Health inequalities in morbidity and mortality between socioeconomic groups have widened in recent years, breaking the trend of convergence observed in the 1950s and 1960s. Theoretically, a wide range of possible mechanisms can explain such changes. Income can, for example, be correlated with risk behaviour, which in its turn has an influence on choices regarding diet, exercise, and smoking. But income also affects the ability to buy different kinds of health goods, for example health treatments, air bags, bicycle helmets, time at gyms, better housing and safer environments. Some of these factors have immediate effects on health, others a long-lasting effect. Conditions early in life can, for example, influence the development of cardiovascular diseases, respiratory and allergic diseases, diabetes, hypertension and obesity, breast and testicular cancers, neuropsychiatric and certain other disorders. And some diseases are transferred from one generation to the next. Thus, while a long-term perspective seems necessary in all studies of health, most findings so far stem from cross-sectional studies.
The research conducted in this area can be dividen into four partly overlapping sub-areas; 1) the effects of social contexts and geographic areas/neighbourhoods on health and social inequalities, 2) impacts of early-life factors on health later in life, 3) effects of conditions in early life on later life mortality, and 4) impacts of intergenerational transfers on health.