Health of individuals and populations is determined by a number of factors, some modifiable and some non-modifiable. Whether people are healthy or not is determined to a large extent by their circumstances and environment. Factors such as access and use of healthcare services often have less of an impact.

Factors such as age, gender, ethnicity and genes are considered non-modifiable determinants of health. Factors that can be modified include lifestyle factors (smoking, alcohol, physical activity, diet), environmental factors (geography, air and water quality), socio-economic factors (occupation, income, education) and wider societal factors (macroeconomic conditions, healthcare, sanitation). Some of these factors can be addressed at individual level while others may be addressed at group level. The ‘rainbow’ model by Dahlgren and Whitehead (Figure 19a) provides a useful model to think of these influences.