Midlife Chronic Disease Increases the Risk of Late Life Dementia
People exhibiting chronic disease in middle age, such as type 2 diabetes or other lifestyle conditions brought on being overweight and sedentary, have a greater risk of dementia in later life. A sizable amount of evidence exists to support this relationship, and the point is once again illustrated by the data presented in this open access paper. Maintaining good health has a great deal of value, especially in an era of progress towards therapies to slow and reverse aspects of aging. Being in better health in late life will mean a greater ability to take advantage of therapies that will further improve and lengthen healthy life span.
A further consequence of population ageing is the increase in multimorbidity, conventionally defined as the presence of two or more chronic diseases irrespective of the severity of such conditions. Recent estimates suggest that more than 50% of older adults in high income countries report multiple chronic conditions, although multimorbidity is not confined to older adults. The development of chronic diseases at younger ages has implications for their management, the risk of premature mortality, and the cost of care. Multimorbidity is estimated to have an adverse effect on patients' outcomes and healthcare systems that is greater than that of chronic conditions considered indivdually.
In older adults with dementia, the presence of several comorbid conditions is common. A recent study of older adults (mean age 75 years) followed for a mean of 8.4 years reported higher risk of dementia in those with multimorbidity, but studies that have followed individuals for longer are lacking. Recent studies also suggest that the risk of dementia is higher in people with cardiometabolic disease in midlife rather than late life, suggesting that age at onset of multimorbidity is an important determinant of risk of dementia.
Accordingly, we examined whether longer duration of multimorbidity and severity of multimorbidity (defined as three or more chronic conditions), implying earlier age at onset of multimorbidity, increase the risk of dementia at older ages in the Whitehall II cohort study spanning 30 years. The prevalence of multimorbidity (≥2 chronic diseases) was 6.6% (655/9937) at age 55 and 31.7% (2464/7783) at age 70; 639 cases of incident dementia occurred over a median follow-up of 31.7 years. After adjustment for sociodemographic factors and health behaviours, multimorbidity at age 55 was associated with subsequent risk of dementia, hazard ratio 2.44. Multimorbidity, particularly when onset is in midlife rather than late life, has a robust association with subsequent dementia. The increasingly younger age at onset of multimorbidity makes prevention of multimorbidity in people with a first chronic disease important.