Social and biological determinants of cognitive aging.

The aging of populations increases the importance of cognitive function as a public health issue. The Whitehall II study is investigating influences on aging processes within social context, with tests in five domains of cognitive function (short-term memory, inductive reasoning, vocabulary, phonemic and semantic fluency). The tests have now been completed three times over a 10-year period, by participants initially aged 40-60 years. In mid-life, socioeconomic differences in cognitive function were large, while APOE genotype had little influence. Higher occupational status was strongly related to lower metabolic syndrome prevalence. This social-biological gradient illustrates that potential confounding of psychosocial, behavioral and biological effects on cognitive decline is an important consideration in etiologic research. Additionally, it highlights the importance for population health of the 'causes of the causes' of cognitive aging. Epidemiology contributes to our understanding of risk and protective factors for cognitive decline by showing the links between the wider determinants of health and biological markers such as glucose intolerance and the metabolic syndrome.