Eliminating depression, diabetes can reduce levels of dementia: Study

Research: Designing prevention programs to reduce incidence of dementia: Prospective cohort study of modifiable risk factors

Eliminating diabetes and depression, as well as increasing education and fruit and vegetable consumption, are likely to have the biggest impact on reducing levels of dementia in the coming years, should no effective treatment be found, concludes a study published on bmj.com today.

These findings suggest priorities for future public health interventions.

While the exact cause of dementia is still unknown, several modifiable risk factors have already been identified. These include vascular risk factors (heart disease, stroke, high blood pressure, obesity, diabetes, and high cholesterol), a history of depression, diet, alcohol consumption, and education level.

Based on this knowledge, a team of researchers based in France and the UK estimated which of these risk factors might be most effective in reducing the future burden of dementia, should no effective treatment be found.

Their analysis involved 1,433 healthy people aged over 65 years living in the south of France and recruited between 1999 and 2001. Participants underwent cognitive testing at the start of the study and again at two, four and seven years. A reading test (the Neale score) was also used as an indicator of lifetime intelligence.

Medical history and information on measures such as height, weight, education level, monthly income, mobility, dietary habits, alcohol consumption, and tobacco use was obtained. An individual's genetic risk of dementia was also measured: although it's not a factor that can be changed it served as a useful benchmark for dementia risk.

Results showed that eliminating depression and diabetes and increasing fruit and vegetable consumption were estimated to lead to an overall 21% reduction in new cases of dementia, with depression making the greatest contribution (just over 10%). However, the researchers point out that the direct (causal) relationship between depression and dementia remains unclear.

Increasing education would also lead to an estimated 18% reduction in new cases of dementia across the general population over the next seven years. By contrast, eliminating the principal known genetic risk factor from the general population would lead only to a 7% reduction in the number of new cases over the next seven years.

Given these findings, the authors suggest that public health initiatives should focus on encouraging literacy at all ages irrespective of ability, prompt treatment of depressive symptoms, and early screening for glucose intolerance and insulin resistance (early stages in the development of diabetes).

While these calculations can only provide a crude estimate of impact on incidence, they do make a significant statement about public health priorities in disease prevention in the face of current knowledge, conclude the authors. Further studies including younger adults are clearly needed to test the impact of intervention measures.

A second study, also published on bmj.com today, finds that death rates are more than three times higher in people with dementia than in those without dementia in the first year after diagnosis. The study also says that earlier and better detection of dementia in primary care is needed. An accompanying editorial suggests that key areas to focus on include better education and training in primary care, developing more integrated systems of care, and ensuring that policy makers and commissioners plan services that reflect the effects of dementia on primary care and other services.