Behavioural risk factors
Prevention of dementia
Regular and high intensity leisure time physical activities (e.g. dancing, walking) seem to reduce dementia risk. In a population based study, leisure-time physical activity at midlife at least twice a week was associated with a reduced risk of dementia and AD.
A prospective cohort-study in the USA found that incidence rate of dementia was 13 per 1000 person-years for participants who exercised 3+ times/week compared with 19.7 per 1000 person-years for those who exercised fewer than 3 times/week. Risk reduction associated with exercise was greater in those with lower performance levels/ poorer physical functioning at baseline. Data from the Canadian Study of Health and Aging have associated regular physical activity (defined by a simple “yes/no” question) with a reduced risk of AD. The CAIDE study showed that regular leisure time physical activity at midlife may protect against dementia and AD later in life. The risk reduction was 50% for dementia and 60% for AD. Associations between increased activity and decreased risk seem to be more pronounced among the APOE 4 carriers. Regular physical activity may reduce the risk or delay the onset of dementia and AD, especially among genetically susceptible individuals. Social and mental activities have also been suggested to protect against AD. Generally, an active lifestyle may increase cognitive reserve capacity, reduce stress and thus protect against development or expression of dementia.
Cognitive activity / education
A higher level of education appears to reduce the risk for dementia. More frequent participation in cognitive activity is associated with reduced incidence of dementia. A cognitively inactive person seems to be more likely to develop AD than a cognitively active person. Frequent cognitive activity was also associated with reduced incidence of mild cognitive impairment and less rapid decline in cognitive function.
There even appears to be a dose-response relationship of education, each additional year of formal education further delays the time of accelerated cognitive decline.
Living alone, having no close social ties, not participating in social and leisure activities and never having married seems to increase dementia risk. Recent studies have found that Alzheimer´s disease in particular is negatively associated with diversity of activities and intensity of intellectual activities and positively associated with psychosocial inactivity, unproductive working style, living with a dominant spouse and physical inactivity. A potential protective effect of the psychosocial network on dementia can be demonstrated in several studies. Multivariate analyses suggest an independent effect, especially of sports and cultural activities, and of the number of confidants. There seems to be a decreased risk for dementia for high challenge at work, high control possibilities at work, and high social demands at work.
Subjects with high leisure activity seem to have less risk of developing dementia. Reading, visiting friends or relatives, going to movies or restaurants, and walking for pleasure or going for an excursion seem to be most strongly associated with a reduced risk of incident dementia. In the Bronx Aging Study, leisure activities, reading, playing board games, playing musical instruments, and dancing were associated with a reduced risk of dementia.
A population-based study of Swedish twins suggests that greater complexity of work, and particularly complex work with people, may reduce the risk of AD. Several studies of the relationship between the psychosocial network or activity level and dementia have focused only on a short time span before the onset of clinical dementia.
These results point to a possible independent protection against dementia from social relationships and from physical and intellectual activities in midlife, possibly also in later life.
Cohort studies have yielded inconsistent results, with some indicating a statistically significant increased risk for AD with history of depression. Meta-analytic evaluation of depression and risk for AD concluded an elevated risk for dementia in people previously diagnosed with depression. History of depression, and particularly an early onset, but not presence of depressive symptoms increased the risk for AD. Interval between diagnoses of depression and AD was positively related to increased risk of developing AD, suggesting that rather than a prodrome, depression may be a risk factor for AD. To date, no evidence exists to answer the question whether early detection and successful treatment of depression in the elderly (or perhaps in younger people) reduce the risk for subsequent AD. Therefore, no clear guidelines can be given.
Measures of work-related stress (job dissatisfaction and high job demands) seem not to be associated with dementia risk many years later. Greater reactivity to stress seems to predict higher risk of dementia controlling for age, education, sex, occupational status, alcohol use, and smoking status. Looking at monozygote twins, co-twin control analyses also showed that dementia probands were more likely to report high reactivity to stress than their co-twins who did not have dementia. Overall, indicators of stress due to environment were not associated with dementia, whereas the individual characteristic of reactivity to stress predicted dementia risk. Distress proneness was also associated with more rapid cognitive decline. Whether psychotherapy that could lead to more stress tolerance could decrease risk in vulnerable individuals is not known.
Last Updated: Thursday 08 October 2009