Doctor–patient relationship

The doctor–patient relationship can influence communication about asthma management, health outcomes and compliance with medication. A study found that asthma outcomes improved when patient’s physicians encouraged them to participate in decisions about their health care, that contributed to improved quality of life, work disability and need for acute health services.²⁵ Greater participation occurred most commonly with longer consultations and when the patient had seen the same physician for more than 6 months.

Affluent countries and economic development

A global research study evaluating over 54 000 people using standardised questionnaires identified the link between economic development and risk of asthma and atopic sensitisation.²⁶ Children in affluent countries were significantly more likely to have an association with current wheeze, allergy-related asthma, and positive skin prick sensitivity compared with children in less affluent settings. Affluent children with allergic sensitisations were 4.0 times as likely to have asthma compared with non-sensitised children, whereas, children in non-affluent countries were only 2.2 times more likely to have an allergic response and asthma compared with non-sensitised children in the non-affluent countries.

Migration

Worldwide figures highlight a significant rise in asthma prevalence and studies amongst migrant populations indicate environmental risk factors may play a role.

A large-scale international study of 7794 Chinese adolescents in China and Hong Kong and 2235 Chinese adolescents living in Vancouver, Canada, found the prevalence of asthma was lowest in residents of mainland China compared with those of Hong Kong and those who immigrated to Canada or were born in Canada.²⁷ The incidence for ‘current wheezing’ among boys and girls ranged from 5.9% and 4.3% in Guangzhou (mainland China) respectively, and 11.2% and 9.8% in Canadian-born Chinese adolescents respectively. The prevalence of ever having had asthma ranged from 6.6% (Guangzhou) to 16.6% (Vancouver) for boys and from 2.9% (Gangzhou) to 15.0% (Vancouver) for girls, suggesting asthma symptoms in Chinese adolescents were lowest among residents of mainland China and were greater for those born in Canada. The study also demonstrated that asthma prevalence was higher for Chinese born in Hong Kong and Chinese migrants in Canada. These findings suggest that environmental factors may influence asthma prevalence.

Research involving 211 Australian students who migrated from Asia, the South Pacific, the Middle East, Europe and Africa, demonstrated the prevalence of adolescent migrants living in Australia with asthma was higher compared with similar age groups in their home countries.²⁸ The risk of developing asthma increased by 11% for every year they lived in Australia.

Travel

Travel is a risk factor for asthma — a study of 203 asthmatics visiting 56 countries found frequent use (> or = 3 times weekly) of inhaled bronchodilators before travel and participation in intensive physical exertion during treks significantly increased the risk of asthma attacks.²⁹ Asthmatics should avoid intensive trekking.

Low socioeconomic status (SES)

A US twenty year follow-up study of adults and children demonstrated low socioeconomic status had a negative impact on lung function, after adjusting for smoking status, occupational exposures, and race.³⁰ Researchers reported reductions of forced expiratory volume in 1 second (FEV₁) of greater than 300 mL in men and 200 mL in women of low SES compared with high SES.

There are multiple risk factors that may contribute toward the causation and pathogenesis of asthma. Table 5.2 summarises causes and/or triggers of asthma. These are discussed in detail throughout the chapter.

Table 5.2 Risk factors for asthma

General risk factors

A study of Australian rural NSW children aged 3–5 years estimated the prevalence of asthma between 18–22%, and identified clear risk factors for asthma.³¹ The risk factors which doubled the risk of developing asthma included: atopy; having a parent with a history of asthma; having had a serious respiratory infection in the first 2 years of life; and a high dietary intake of polyunsaturated fats. Protective risk factors include breastfeeding and having 3 or more older siblings.

Other risk factors for asthma include: family history (maternal asthma odds 2.4; paternal 2.1); smoking (1.7 fold); serious respiratory infection before age 5 (2.3 fold); positive skin test to cladosporium (mould), house dust mite (HDM), cat and rye grass pollen; and occupational exposure to allergens.³² Avoidance to these irritants may be of help (see Table 5.3).

Table 5.3 Possible allergen triggers especially in high risk asthmatics³³

Allergens, allergic triggers

There are a number of preventative methods to help reduce or avoid exposure to allergens or triggers of allergy or asthma. These methods play a more important role particularly in children who are atopic or at risk of developing atopic disease (high-risk infants) and children with early symptoms of allergic disease. This may improve control of asthma and reduce the need of medication.

Asthma patients may benefit from simple avoidance strategies for allergens when and where possible. Advice on effective strategies is an essential part of managing allergic asthma.

Caesarean section

Children born by caesarean section are at a higher risk of developing asthma later in life, and the risk was higher if either or both parents were atopic.³⁴

Breastfeeding

Exclusive breastfeeding in the first 3–4 months of life significantly reduces the risk of asthma and atopy. Multiple studies including systematic reviews and meta-analyses have consistently supported this association. ^35–39 Also duration of breastfeeding is significant with longer duration greater than 9 months being protective towards risk of asthma and wheeze.⁴⁰ Furthermore, a prospective birth-cohort study of over 2000 children from antenatal clinics up to 6 years of age, demonstrated children given non-human breast milk in the first 4 months of life were 40% more susceptible to wheeze 3 or more times since 1 year of age.⁴¹

The beneficial effect is postulated to be caused by immunomodulatory qualities of breast milk, avoidance of allergens, or a combination of these factors. Interesting, whilst breastfeeding was protective, the association of asthma and breastfeeding was increased in atopic children of asthmatic mothers after 6 years of age.⁴² Another study failed to demonstrate protective effects of breastfeeding.⁴³ A study of the maternal diet of breastfeeding mothers demonstrated that atopic mothers had a higher intake of total fat and saturated fat and a lower intake of carbohydrate as a percentage of total energy intake compared with non-atopic mothers and was associated with atopic sensitisation of the infant which may explain the higher risk.⁴⁴ Also higher intake of food allergens may also contribute to this association in atopic mothers.⁴⁵

Breast milk can contain significant numbers of bifidobacteria with studies demonstrating maternal fecal and breast milk bifidobacterial counts impact on the infants’ fecal Bifidobacterium levels and provide an important source of bacteria in the establishment of infantile intestinal microbiota. A study found allergic mothers had significantly lower amounts of bifidobacteria in breast milk compared with non-allergic mothers and this may impact on the risk of the infant developing allergic disease.⁴⁶

Of 448 children with a parental history of atopy, children put to bed with a bottle in the first year of life were at higher risk of wheezing at 1–5 years of age.⁴⁷ The researchers postulated that bronchospasm may be caused by repeated airway irritation due to postprandial reflux.

Antibiotic use and early exposure to respiratory infections

Research indicates that antibiotic use in early infancy (i.e. first 2 years of life) is associated with a 2–3 fold increased risk of developing asthma and hay fever, recognising the role of infections in protecting against asthma.⁴⁸ The study found that the number of courses of antibiotics during the first year of life was also associated with significant increased risk of asthma with 1–2 courses, but particularly with 3 or more courses when compared with no antibiotic use in the first year of life. In another study involving 1035 children followed up since birth, young children exposed to older children at home or to other children at day care are at increased risk for infections, which in turn may protect against the development of allergic diseases and asthma later in childhood. ⁴⁹ Another study also found a significant association between antibiotic use and day care in the first year of life and wheezing at 7 years of age.⁵⁰ Similarly antibiotic use in the first year was significantly associated with greater risk of asthma at age 7 years, particularly with the number of antibiotic courses.⁵¹ Compared with children who did not have antibiotics, children who received more than 4 courses of antibiotics were 1.5 times more likely to develop asthma.

Overall, research assessing children who enter day care at an early age, demonstrates exposure to infections in early childhood may prevent and lower the risk of allergy later in life.^{52, 53} This supports the theory that exposure to infections early in life determines the way the immune system is stimulated, with T-helper cells geared toward fighting infection rather than produce cytokines that promoted allergy.

However, more recent studies found no association of antibiotic use and asthma prevalence suggesting that the reason that some children who’ve been given antibiotics appear to develop asthma is because the symptoms of the chest infection in young children can be confused with the start of asthma.^{54, 55}

Medication

A retrospective study demonstrated that children medicated with paracetamol in the first year of life, are at higher risk of developing asthma; by up to threefold for frequent use.⁵⁶ Similarly another study found regular paracetamol intake in pregnancy has also been associated with greater risk of developing asthma by 60%, and even up to 85%, in offspring.⁵⁷ The mechanism behind this finding is not clear. There are many medications known to aggravate asthma such as beta-blockers, non-steroidal anti-inflammatories, aspirin and even the oral contraceptive pill which should be used with caution or avoided in asthmatics.⁵⁸

The modern diet and obesity

The modern diet low in fresh foods such as fruit, vegetables and fish may be responsible for the rise in asthma. Obesity may be a contributor to allergies. Obese children are at greater risk of asthma, especially girls, according to the UK National Study of Health and Growth in London, which surveyed 15 000 children, aged 4 to 11, independent of ethnicity.⁵⁹ Obese children are 26% more likely to be more atopic, and sensitivity to milk was at least 50% higher than in normal-weight children.⁶⁰ Mean total IgE levels were higher among obese and overweight children than normal-weight children. The risk for atopy (any positive specific IgE measurement) was increased in the obese children largely driven by allergic sensitisation to foods.

Also, abdominal adiposity is known to compromise respiratory lung capacity.^{61, 62, 63}

Mattresses

Sleeping on used cot mattress in the first year of life is associated with increased risk of asthma.³⁷ The study assessed 871 New Zealand children of European descent at birth and ages 12 months, 3.5 years and 7 years. The study found that 24% of children suffered from wheezing at 3.5 years and 18% at 7 years when they had a history of sleeping on a used cot mattress. In this study, other than the use of a used cot mattress for sleeping, asthma was also associated with maternal smoking during pregnancy, being in day care, antibiotic use, and the presence of a dog.

Stressful events

Children born to mothers who suffer chronic stress during their early years have a higher risk of asthma rate compared with their peers according to a cohort study of 14 000 children. This finding was independent of income, gender, maternal asthma, urban location or other known asthma risk factors.⁶⁴ The mechanism for how maternal distress causes asthma is not well understood although depressed mothers were more likely to smoke, less likely to breastfeed and less likely to interact with their infants.

Maternal stress and anxiety in pregnancy during fetal life is a risk factor for asthma during childhood. A longitudinal study of 5810 children recruited during pregnancy found a higher incidence of asthma in children at age 7 with mothers who experienced highest levels of anxiety at 32 weeks gestation compared with mothers with lowest levels of anxiety.⁶⁵ Poor coping in parenthood is also a known risk factor. Of 150 middle- to upper-class children followed up from birth to 6–8 years of age, one-quarter developed asthma. Both serum IgE levels and parenting difficulties were associated with increased risk of asthma. The researchers concluded that emotional stress may alter both immune and respiratory responses and their results ‘should reinforce the importance of providing support and education to new parents and their children’.⁶⁵

Acute stressful events and negative life events increase the risk of asthma exacerbations in a study of 90 primary-school Scottish children, particularly in children suffering multiple chronic stressors.⁶⁶ Asthma was self-monitored twice a week for 3 months. Acute negative events, such as family break-up and death of a grandparent increased the risk of suffering asthma. The risk of asthma attacks increased significantly when the acute stress was added to chronic stress such as poverty, family discord, parental substance abuse or being bullied at school.⁶⁷

Stress appears to be a risk factor for asthma.⁶⁸

Post–traumatic stress disorder (PTSD)

A study of 3065 male twin pairs (monozygotic and dizygotic twins), who lived together in childhood and served on active military duty during the Vietnam War, found those who suffered greater PTSD symptoms were 2.3 times as likely to have asthma compared with those who suffered from the least PTSD symptoms.⁶⁹ These findings suggest the emotional association between asthma and PTSD occurred despite twins sharing similar genes. The authors postulated that traumatic stress compromises the immune functioning independent of genes.

General

A review of the literature noted psycho-educational self-management programs, relaxation therapy, biofeedback, and family therapy to be particularly useful in improving asthma outcome and significant beneficial effects were found for relaxation therapy. The researchers also identified biofeedback for ‘respiratory resistance, trachea sounds, and vagal tone’ to show promise.⁷⁰

A Cochrane review of psychological interventions for adults with asthma identified 15 studies, involving 687 participants, aimed at determining the effect of cognitive behaviour therapy (CBT) on quality of life, and biofeedback and relaxation therapy on pulmonary function, FEV₁ and medication use.⁷¹ They found conflicting results but overall quality of life improved with CBT and reduced the use of ‘as needed’ medications. Relaxation therapy also reduced the need for ‘as needed medications’ although no significant differences in FEV₁ was found. Biofeedback improved asthma and lung functions such as peak expiratory flow rate and FEV₁ in 2 studies.

Another Cochrane review assessing psychological interventions for children with asthma found conflicting results amongst the 12 studies of 588 children. Two studies examining the effects of relaxation therapy on peak expiratory flow rate (PEFR) significantly favoured the treatment group (32 L/min, 95% CI 13 to 50 L/min).⁷²

So, based on the findings of these Cochrane reviews, it appears relaxation therapy, biofeedback and CBT can play a role in asthma management to improve quality of life, pulmonary function and the need for ‘as needed’ medication in adult and child asthmatics.

Spiritual healing

An innovative study tried to examine if spiritual healing could assist asthma. Spiritual healing was of no benefit for asthma symptoms when compared with sham healing and control.⁷³

Psychological counselling

Psychological interventions can help reduce the burden of asthma symptoms and improve the management of disease and compliance with medication.

Depression and anxiety are more prevalent in severe asthmatics and associated with greater morbidity, mortality and non-compliance, requiring close psychological monitoring and the potential role for effective counselling in young asthmatic patients.^{74, 75, 76} One study of over 1300 youths aged 11 to 17 years found young people with asthma were twice as likely to suffer depression and anxiety disorders compared with children without asthma.⁷⁷

A population survey of 3010 participants aged 15 years and over found the prevalence of asthma was 9.9% and identified major depression was significantly higher for those who experienced dyspnoea, wakening at night from asthma, morning symptoms of asthma and reduced quality of life compared with those who did not suffer asthmatic symptoms.⁷⁸

A case-controlled study of 21 patients from 8 to 18 years of age with severe asthma who were hospitalised and who died of asthma subsequent to discharge identified psychologic risk factors were prominent, such as conflicts between patients’ parents and hospital staff regarding medical management, depressive symptoms and disregard of asthmatic symptoms.⁷⁹

Psychological approaches such as counselling and biofeedback-assisted relaxation therapy were found to be particularly useful in improving mood and asthma.^{80, 81, 82}

Family therapy

Asthma can be quite stressful for families and can impact parenting and interaction between family members.^{83, 84, 85} Children of parents who experience major depression or panic attacks are also more likely to develop atopic disorders by 67% and 46% respectively.⁸⁶ Children with a genetic predisposition to asthma are 3 times more likely to express the illness with domestic stresses and parenting. ^{87, 88} Research supports the role of family therapy in asthma management.⁸⁹

Relaxation therapy and meditation

Given that stress may exacerbate asthma, there is a role for stress management in the prevention and management of asthma. A review of the literature of variable quality studies demonstrated that stress can produce bronchoconstriction.⁹⁰

Relaxation therapy is associated with respiratory muscle relaxation, reduced panic, reduced airway reactivity, improved lung function, promotion of diaphragmatic breathing, reduction in metabolic rate and may have an anti-inflammatory effect. A study found transcendental meditation (TM) can improve respiratory function.⁹¹ This 6 month study, with cross-over at 3 months, demonstrated TM can be a useful adjunct to asthma treatment.

However, a UK systematic review of the literature found overall, the methodological quality of the 15 randomised clinical trials (RCTs) on relaxation therapy assessed were poor and better quality studies are required.⁹²

In addition to the abovementioned research, it was found that music therapy can be particularly helpful for relaxation and asthma.⁹³

Despite these findings, generally patients with asthma who practise regular relaxation therapies experience improved quality of life.

Biofeedback

Fear and panic are common emotions experienced by asthmatics.^{94, 95, 96}

A review of the literature identified negative emotions such as panic and generalised panic disorder are common in asthmatics. These negative emotions can also affect asthma morbidity.⁹⁷ They identified self-regulation strategies as useful adjuncts to asthma treatment such as relaxation therapy, electromyographic (EMG) biofeedback, biofeedback to improve sensitivity in perceiving symptoms, and biofeedback training for increasing respiratory sinus arrhythmia. Relaxation-oriented methods were more beneficial amongst asthmatics with panic symptoms.

A number of studies demonstrated that biofeedback is helpful for dealing with asthma symptoms in children and adults.^{98, 99} A 15 month follow up of asthmatics that included a comprehensive multi-behavioural and desensitisation retraining program using EMG and spirometer feedback to encourage slow diaphragmatic breathing in all situations, demonstrated subjects reported reductions in their asthma symptoms, medication use, emergency room visits, and breathless episodes.¹⁰⁰

Electromyographic feedback methods can also be useful by providing feedback on muscle tension and strain.^{101, 102}

Hypnosis

A prospective, randomised, single, blind controlled trial of 39 adults with mild to moderate asthma after a 6-weekly course of hypnotherapy demonstrated a 75% improvement in the degree of bronchial hyper-responsiveness, improved peak expiratory flow rates by 5.5%, and reduction of use of bronchodilators by 26% in the more highly susceptible subjects to hypnosis.¹⁰³ Daily home recordings of symptoms also improved.

Another study of severe chronic asthmatics inadequately controlled with medication undergoing relaxation induced hypnotherapy reported: improved asthma symptoms; a significant reduction in hospital admissions, from 44 to 13 a year in total; reduced duration of hospitalisation; and reduction of prednisolone use and side-effects experienced from medication.¹⁰⁴ Air flow tests remained variable among subjects.

Journal writing

A study of patients with mild-moderate asthma or rheumatoid arthritis demonstrated that writing about emotionally traumatic life experiences over a 4-month period can help reduce chronic disease symptoms.¹⁰⁵ With asthma, lung function test forced expiratory volume in 1 second (FEV₁) improved from 63.9% at baseline to 76.3% at the 4 month follow-up period of journal writing, with no change in the control group. The rheumatoid arthritis patients also did well with significant reduction of symptoms and disease activity compared with the control group.

In an RCT 137 adult asthmatic patients were randomly assigned to write for 20 minutes, once per week for 3 weeks, about stressful life experiences (n = 41), positive experiences (n = 37), or neutral experiences (n = 36; control group).¹⁰⁶ The study found only marginal benefit for FEV₁ and for forced vital capacity (FVC) between each group: the stress-writing group demonstrated 4.2% FEV₁ and 3.1% FVC improvement, the positive-writing group 1.3% FEV₁and 3.6% FVC, and in the control group 3.0% FEV₁ and 2.4% FVC.

Laughter

Laughter and excitement can also trigger asthma, such as cough and dyspnoea, with cohort studies suggesting the incidence is common, estimated at 32% in young asthmatics.¹⁰⁷ The researchers examined 285 children who had experienced an acute asthma attack and found ‘mirth-triggered’ asthma, especially cough symptom, occurred within 2 minutes of laughing.

Mirth-triggered asthma is an indication of sub-optimal asthma control and treatment.

Pet ownership

Allergens are a common cause for triggering asthma attacks. Allergens from pet and animal hair can trigger symptoms in an atopic asthmatic.

Pet keeping in early childhood can impact on allergies and asthma depending on the type of pet, the age and the allergic sensitisation of the individual.¹⁰⁸ A review of the literature found recent published studies have produced heterogeneous results.¹⁰⁹ Sensitisation to pets is a risk factor for asthma and can occur in children who live in homes with no pets and with low levels of pet. allergen. The authors of the review conclude ‘excluding pets from the home will not necessarily protect children from the development of sensitisation to pets’.

Another systematic review found exposure to pets increases the risk of asthma in children over 6 years of age.¹¹⁰

A large international survey of almost 19 000 adults found the effects of having pets during childhood varied according to the type of pet, the allergic sensitisation of each subject and pet prevalence in the community.¹¹¹ The survey indicated that keeping a cat doubled the risk of asthma, but only among atopic subjects.

However, dogs kept in early childhood protect against allergic sensitisation and protect against hay fever symptoms in atopic subjects. Those who were not atopic had an increased risk of adult respiratory symptoms with early dog exposure. Having birds in childhood was associated with more adult respiratory symptoms independent of atopic status. These findings confirm that early exposure to animals in early life does influence the development of the immune system and the airways, with the potential to promote or prevent subsequent disease in later adulthood.

Exposure to a dog in early infancy may protect against atopy due to mediation of cytokine response.^{106, 112} Further research studying 285 infants demonstrated that children who grow up with a pet dog were less likely to develop allergic sensitisation and atopic dermatitis.¹¹³ The rate of allergic sensitisation was 14% lower and the rate of atopic dermatitis 21% lower in children with a dog compared with children with no dog. Similarly, studies suggest early exposure to pets can be protective towards asthma development.^{114, 115}

A recent study of 275 children (3 years of age) at increased risk of developing allergic diseases found exposure to dogs in infancy, and ‘especially around the time of birth, is associated with changes in immune development and reductions in wheezing and atopy’.¹¹⁶

A community sample of 3181 adults aged 26–82 years found keeping a cat or dog in childhood was associated with increased risk of dyspnoea or breathing difficulties.¹¹⁷ Based on current evidence there are mixed findings to pet ownership but it appears dogs may offer some benefit in reducing development of asthma risk in atopic children.

Thunderstorms

Asthma epidemics may be linked with thunderstorms as pollen counts are high during these times. A deluge of grass pollen during thunderstorms may be the cause of epidemic asthma. It may be wise for asthmatics to stay indoors during thunderstorms. The risk of symptoms doubled if asthma patients were outdoors during thunderstorms, according to an analysis of data of 183 patients following a spring storm.¹¹⁸ Asthmatics sensitive to thunderstorms also tend to suffer hay fever and are allergic to rye grass pollen compared to control groups.^{119, 120}

Weather

A change of weather may impact on asthma. Triggers of asthma include changes in temperature; cold windy days; hot humid days; and poor air quality.

Farm children

A study surveyed 1333 farmers’ children and a reference group of 566 children aged from 5 to 17 years and found that children with both prenatal and current exposure to farm animals and plants were up to 50% per cent less likely to have allergies such as asthma, eczema and hay fever than the reference group.¹²¹

House dust mite (HDM)

House dust mite (HDM) is a major allergen found in house dust. There are various methods available to reduce HDM allergens by chemical or physical means, with the aim to reduce asthma symptoms in those who are sensitive to HDM. There are many studies finding links between HDM and allergic and asthma symptoms. Seasonal fluctuations of HDM numbers determined by humidity in children’s beds may contribute to fluctuations and influence asthma symptoms.¹²²

A large-scale prospective birth-cohort study of 939 newborns, followed up until 7 years of age, cast doubt on the theory of early exposure to HDM allergens as a primary cause of asthma in young children.¹²³ The study did show that children with asthma were more likely to be sensitised to HDM and cat allergens, but those were not the ‘cause’ of asthma.

Whilst studies show mixed results, the weight of evidence supports reducing HDM levels in households. Advice to parents to reduce HDM exposure to infants and asthmatics includes: removal of old carpet; use of closely woven dust mite covers on bedding; frequent airing of blankets and mats; keeping indoor humidity low; using hydronic heating instead of central heating; and using damp cloths for wiping surfaces.

Bedding and mattress protectors

Higher HDM antigen levels in bedding appear to be a risk factor for persistent bronchial hyper-reactivity in adolescence.¹²⁴ Exposure to HDM in temperate climates is the strongest environmental risk factor for asthma. A study of 616 pregnant women were randomised to HDM intervention by using impermeable mattress covers and an acaricide washing detergent for bedding. When compared with the control group, these methods were effective in reducing HDM allergens.¹²⁵

Laundry washing

Washing laundry at 25 degrees Celsius for at least 5 minutes was sufficient to remove most of the cat and mite allergens, according to an Australian study.¹⁴⁰ There were no distinct differences between which laundry detergents were used and washing at 60 degrees Celsius reduced more allergens, though the benefits were slight.

Physical and chemical methods

A Cochrane review of 54 trials (3002 patients) of which 36 trials assessed physical methods (26 mattress encasings), 10 chemical methods, and 8 a combination of chemical and physical methods, found most trials were of poor quality and the interventions were statistically of no benefit for health outcomes and asthma symptom score.¹⁴¹ Similarly, a report published in Cochrane PEARLS (Practical Evidence About Real Life Situations) concluded HDM control measures may not reduce asthma symptoms.¹⁴²

A study found successful attempts to reduce environmental allergens such as avoidance of HDMs, pets, tobacco smoke, promoting longer breastfeeding and avoiding early introduction of foods significantly reduced the risk of asthma by 60% and wheeze by 90% in 2-year olds compared with the control group.¹⁴³ Table 5.4 provides simple strategies for reducing allergen exposure at home.

Table 5.4 Simple measures for reducing environmental allergens

Damp houses and mould

Dampness in the house is also a risk factor for asthma.

A Munich study of 234 children with asthma, demonstrated that living in damp houses plays a significant risk factor for asthma with increased nocturnal wheeze, shortness of breath and persistence of bronchial hyper-reactivity in adolescence.¹⁴⁸ This risk was not attributed or explained by exposure to HDM antigen.

The Skorge et. al. study also found an association of mould exposure with all the respiratory symptoms such as cough and dyspnoea with 3–5% of the frequency of the respiratory symptoms in the study population attributed to exposure to visible moulds.¹¹⁷ Of interest, fitted carpet in the bedroom reduced the risk of respiratory symptoms.

A population-based case–control study that involved researchers visiting and assessing the homes of 121 asthmatic children and 241 controls found visible moisture damage and mould growth in the main living quarters (living room or child’s bedroom) was significantly associated with the development of asthma in early childhood.¹⁴⁹

Occupational asthma and chemical exposure

Occupational asthma is caused by reactions to allergens in the workplace.² The report, Occupational Asthma in Australia, indicates 9–15% of adult-onset asthma cases can be attributed to exposure to causal agents at work such as wood dust, paint fumes, solvents, latex and baking flour.¹⁵⁰ The commonest causes of occupational asthma in Australia are wood dust from trees such as the Western red cedar, isocyanates (the raw materials used in polyurethane products), paint fumes, solvents, latex, and flour.

One of the largest population studies of occupational asthma that analysed data on 15 637 randomly selected people aged 20–44 from 26 areas of 12 industrial countries estimated the incidence of occupational asthma in young people at 5–10%.¹⁵¹ A recent population-based study of 13 countries also found that at least 10% of adult onset asthma is related to occupational allergens.¹⁵² Those at greatest risk had a history of atopy or parental asthma. High-risk occupations included farmers, painters, plastic workers, cleaners, spray painters and agricultural workers commonly exposed to chemical substances. Asthma risk was also associated with high exposure to dusts, gases and fumes. People who work in commercial greenhouses are also at risk of occupational asthma if they are sensitised to the flowers they grow, according to German researchers.¹⁵³

Professional and domestic cleaning are also associated with aggravation or inducing asthma due to chemical exposure from cleaning products.^{154, 155} A 9-year European study of 3503 adults free of asthma at baseline, found 42% of the sample study who used cleaning sprays at least once weekly increased the risk of asthma symptoms by 49% and wheeze by 39%.¹⁵⁶ The risk increased with increasing use of cleaning sprays but not liquid products. Glass and furniture cleaning sprays and air-refreshers posed the greatest risk to asthma. The overall prevalence of adult onset asthma related to cleaning sprays was estimated at 15% by researchers.

A study of 4500 Spanish women aged 30–65 years found those who had worked in domestic cleaning had a higher rate of all respiratory symptoms, including asthma compared to those who had never worked in domestic cleaning.¹⁵⁷ It was not clear whether exposure to dust mites, cleaning products or other allergens contributed to the increased risk.

Smoking

The association between smoking (passive and active) and asthma is strong and well accepted. The beneficial effects of smoking cessation on lung function are well established. Smoking should be avoided by asthmatics and smoking indoors avoided by other household members (e.g. parental smoking), as even passive smoking may cause or aggravate asthma.¹⁵⁸

Traffic and air pollution

Air pollution is associated with impaired health, including reduced lung function in adults and children.¹⁵⁹ Air pollution is commonest in major cities and some industrialised areas. Motor vehicles are the main source of air pollution due to particles in suspension, particularly those that use diesel fuel. Air pollution compromises respiratory function. Moving to polluted areas may aggravate lung function in children and adults. A number of studies demonstrate benefit to lung function when children move to cleaner geographic areas.

Epidemiological studies demonstrate an association between the degree of traffic exposure and lung function in asthma. A large-scale study of city school children primarily based in the centre of Oxford (England) demonstrated a statistically significant improvement in peak expiratory flow (PEF) rate and respiratory symptoms among children living where traffic on roads decreased compared to those living where the traffic increased.¹⁶⁰

Exposure to traffic pollution, particularly diesel exhaust, is associated with impaired lung function in asthmatics and the rise of atopy.^{161, 162}

A recent prospective birth cohort study based in Germany of children at the age of 4 and 6 found a strong positive association was found between the distance to the nearest main road and asthmatic bronchitis, hay fever, eczema, and sensitisation, especially in those living less than 50 metres from busy roads.¹⁶³

A study of 460 children in Holland found episodes of wheeze and shortness of breath increased by 140% when exposed to airborne pollutants of small particulate matter and when other pollutants, such as sulphur dioxide and nitrous oxides, were highest.¹⁶⁴ The study found children with bronchial hyper-responsiveness and high concentrations of serum total IgE were more susceptible to health problems from air pollution.

The rise in asthma, allergic rhinitis and atopic eczema may be attributed to a number of combined causes such as air pollution, exposure to diesel exhaust particulates, greater exposure to indoor allergens through adoption of an ‘inside’ lifestyle, artificial ventilation of buildings and changes to outdoor allergen exposure with climate changes.

Climate change

Climate change gives rise to variations in temperature patterns that impact on plants by varying pollination times and favouring some plant species over others. The presence of high CO² concentrations and temperatures can increase pollen counts by plants with the subsequent risk of allergic sensitisation in the human population.¹⁶⁵ For example, an environmentally controlled greenhouse mimicking climate changes by doubling the atmospheric CO² concentration stimulated ragweed-pollen production by 61% suggesting significant increases in exposure to allergenic pollen under the scenario of global warming.¹⁶⁶

A prospective study of 9651 adults (18 to 60 years of age) randomly selected from population registries found an association between indoor and outdoor pollution (particulate air pollution) and decline in lung function, especially of small airway function.¹⁶⁷

Street trees

Children living in areas with more tree-lined streets have lower rates of asthma and a lesser risk of developing asthma, as trees improve air quality or encourage children to play more outdoors.¹⁶⁸ Street trees were associated with a lower prevalence of early childhood asthma.

Indoor pollution

Indoor pollution may play a role in the pathogenesis of childhood asthma but not as the cause of asthma in childhood.¹⁶⁹ There are potentially multiple indoor allergens that can cause sensitisation such as dust mite, cockroach, pet, rodent allergens, and indoor air pollutants; for example, ozone, particulate matter, nitrogen dioxide, environmental tobacco smoke, sulfur dioxide, and carbon monoxide.¹⁷⁰

A study of 409 children in 5 New Zealand communities between the ages of 6 and 12 with diagnosed asthma, were assessed before and after more effective heating was installed in their homes.¹⁷¹ After installing better heating such as heat pumps, flued gas heaters or pellet burners, children demonstrated improved health, less sleep disturbance, reduced asthma symptoms such as wheezing, less coughing at night and overall improved respiratory symptoms. Consequently they had fewer sick days off school and less doctor visits.

A cohort study of children (2–6 years of age) monitored the air in their bedrooms for 3 days to assess the level of indoor pollution specifically for particulate matter, nitrogen dioxide, and ozone.¹⁷² They found the level of bedroom air pollutant concentrations did not differ significantly between asthmatic and non-asthmatic subjects. Whilst these substances may aggravate asthma, the study did not support the causative role of these factors for developing asthma.

Overall a systematic review of the literature supports a link between housing improvement, such as rehousing, refurbishment, and energy efficiency measures and health gains after the intervention.¹⁷³

Of interest, exposure to airborne inhaled allergens released during cooking can provoke asthma in atopic children allergic to foods.¹⁷⁴ The study identified inhaling allergens from foods such as fish, chickpeas, and buckwheat during cooking, and even opening packets of peanuts in a confined space, can provoke an asthma attack. Asthmatics with food allergies need dietary advice and need to be aware of environmental measures that may be required to limit exposure to aerosolised food.

Winter air pollution — wood smoke

High wood smoke for home heating causing indoor air pollution, as measured by particulate matter in smoke, can affect the health of boys with asthma by reducing lung function.¹⁷⁵ The boys who didn’t have respiratory problems such as asthma were not affected, although all the students (with and without asthma) coughed slightly more on high pollution nights from wood chips.

Installing non-polluting heating in the homes of children with asthma can significantly reduce symptoms of asthma, days off school, visits to health care workers and chemists without significantly improving lung function.¹⁷⁶

Swimming pools — chlorine

Swimming offers an excellent way to build up fitness and can improve lung function. However, a number of studies demonstrate exposure to indoor and outdoor chlorinated swimming pools can be detrimental to the airways of swimmers and pool attendants and can be associated with higher risks of asthma, airway inflammation and some respiratory allergies.^177–181

In addition, case reports describe occupational asthma in swimming pool attendants, due to poor air quality above indoor chlorinated swimming pools.¹⁸² It would appear swimming in non-chlorinated pools such as ozone-treated pools or the beach is preferred for asthmatics.

Trekking

Young adults with mild to moderate asthma are at risk of aggravating their symptoms with high-altitude trekking due to cold, dry air and exposure to new allergens. Of the 88 high-altitude trekkers surveyed, 45% noted their asthma worsened, 37% experienced the worst attack in their life and 11% experienced a life-threatening attack.¹⁸⁴

Swimming

While some asthmatics suffer exercise-induced bronchoconstriction, a number of trials have demonstrated the benefits of exercise, such as swimming, that improves aerobic capacity, in the management of asthma particularly.¹⁸⁵ Review of available evidence suggests that swimming induces less severe bronchoconstriction than other sports, due to the high humidity of inspired air at water level. Based on the findings of chlorine induced asthma, it is preferable to swim in non-chlorinated pools, such as ozone-treated pools.

Yoga

A number of yoga studies investigating yoga and breath work for treating asthma have been promising with several randomised controlled trials showing benefit from yoga postures and breathing versus control (usual care).

A double-blind, controlled trial of 56 adult asthmatics on maximum doses of inhaled steroids for poorly controlled asthma were randomised to sessions of Sahaja yoga, a traditional form of ‘yoga meditation’ or a control group for 2 hours on a weekly basis for 4 months. Yoga provided significant benefits in improving asthma hyper-responsiveness at the end of each treatment.¹⁸⁶

University students who practised yoga techniques 3 times a week for 16 weeks reported a significant degree of relaxation, positive attitude, better yoga exercise tolerance and lesser usage of beta adrenergic inhalers compared with control groups, but no significant difference in pulmonary function measured with spirometry between the 2 groups.¹⁸⁷

A study of 53 asthmatic patients compared with 53 control patients practising 65 minutes of daily yoga over 2 weeks resulted in significantly fewer attacks per week, less use of medication and improved PEFR.¹⁸⁸

Similar findings were demonstrated in a study of 570 asthmatic patients, with those undergoing yoga therapy of 2–4 weeks and followed up at 3 and 54 months experiencing significant improvement in PEFR and at least 66% reduction in asthma medication, especially in those who practised consistently on a daily basis for longer periods of time.¹⁸⁹

Yoga breathing exercises (pranayama) statistically significantly reduced the dose of histamine needed to provoke a 20% reduction in FEV₁ in patients with mild asthma compared with the placebo device.¹⁹⁰

Another study demonstrated that a yoga therapy program on 46 indoor patients with chronic bronchial asthma improved exercise tolerance and pulmonary functions, reduced symptom scores and reduced medication requirements, even at 1 year follow-up.¹⁹¹

One trial did not find yoga any different to benefits derived from breath-work and stretching alone. This randomised, controlled, double-masked clinical trial of 62 asthmatics compared the active control involving breath-work and stretching with yoga intervention over a 4-week period.¹⁹² Both groups demonstrated significant improvement in post-bronchodilator forced expiratory volume in 1 second and morning symptom scores at 4 and 16 weeks, but no differences were found between the 2 groups.

Yoga clearly has a potential as an adjunct to asthma management as well as improving quality of life, such as reducing stress symptoms.

Qigong

Qigong, part of traditional Chinese medicine (TCM), combines movement, meditation and breathing techniques. It may assist asthmatics according to a pilot study of 30 patients who demonstrated improved lung function tests (peak flow), reduced emergency hospital visits and sick leave.¹⁹³

Alexander technique

Alexander technique, a physical therapy involving a series of movements designed to correct posture and bring the body into natural alignment, may play a role in management of chronic asthma although robust, well-designed RCTs are required in order to test claims by practitioners.¹⁹⁴

Breathing exercises

Inspiratory muscle training

Inspiratory muscle training to improve inspiratory muscle strength training and endurance, also improved asthma symptoms, reduced hospitalisations for asthma, emergency department visits, absence from school or work, and use of medication in patients with asthma.^{207, 208} These exercises may also benefit patients with cystic fibrosis.²⁰⁹

Buteyko

The buteyko method shows potential but there is still debate until more definitive trials are completed as to whether these benefits are physiological or purely subjective. The high incidence of dysfunctional breathing amongst asthmatics may explain or account for the therapeutic effect of breathing retraining exercises and buteyko method of treating asthma.^{195, 210}

Those practising the buteyko method reduced hyperventilation and their use of beta 2-agonists, with daily inhaled steroid dosage reduced by 49% and observed better quality of life, despite no change in FEV₁ levels.²¹¹ In another study, buteyko significantly improved quality of life and reduced inhaled bronchodilator use.²¹² A study of 69 patients found the buteyko technique improved symptoms and reduced the use of bronchodilator use compared with the pranayama breathing exercises (a yoga breathing technique).²¹³

A blinded RCT comparing buteyko breathing with control in 38 people with asthma (18–70 years of age) over 6 months found no significant change in FEV₁ but a significant reduction in inhaled steroid use of 50% and beta2-agonist use of 85% at 6 months from baseline compared with the control group.²¹⁴ The control group remained unchanged with steroid use and there was an observed reduction of beta2-agonist by 37%.

A 2-year Scottish study of 600 asthma patients (aged 18–69 years) randomised to receive buteyko breathing therapy, standard asthma management by physiotherapists, or continued standard asthma management with medication, found buteyko considerably improved asthma symptoms.²¹⁵ Overall, the buteyko group reduced asthma symptoms by 98%, the need for reliever medications by 98%, preventer medications by 92%, oral preparations by 100%, oral preventers by 96%, and reduced the incidence of colds or viral infections by 20%. This compared with ‘no significant change’ in the other 2 groups.