Midlife income, occupation, APOE status, and dementia: a population-based study

To examine the relationship between socioeconomic factors and APOE carrier status on the development of dementia.

Subjects were derived from random, population-based samples previously studied in surveys carried out in 1972, 1977, 1982, and 1987. After an average follow-up of 21 years, 1449 (73%) subjects aged 65 to 79 years were re-examined in 1998. The diagnosis of dementia among the nonparticipants was derived from patient records of the local hospitals and primary health care clinics.

Low income level at old age was related to dementia, but low income level at midlife was not a risk factor for dementia. Dementia was also associated with decreasing income level, from midlife to old age 21 years later, when dementia was diagnosed. A sedentary occupation (office, service, or intellectual work) was associated with a decreased risk for dementia among participants; however, when the nonparticipants were included in the analysis, the associations were no longer significant. Low educational level and the APOE epsilon4 allele independently increased the risk for dementia.

Reduction in income level during follow-up and low income level at old age might be the consequence of a dementing process rather than being associated with risk evolution of dementia.