Dementia risk ‘doubles’ with two or more chronic health issues at middle age

Having two or more chronic health problems in middle age more than doubles the risk of dementia, according to a study that researchers say underscores the importance of good health earlier in life.

More than 64,000 people are living with dementia in Ireland and about 57 million people are affected globally. The worldwide toll is predicted to nearly triple to 153 million by 2050.

Evidence shows that having multiple conditions is common in people living with dementia. But studies examining whether multimorbidity at an earlier age affects the risk of subsequent dementia are lacking.

To fill this knowledge gap, researchers at University College London and the University of Paris set out to examine the long-term association between multimorbidity at ages 55, 60, 65 and 70 and subsequent dementia.

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Their findings are based on data collected from more than 10,000 Britons taking part in the Whitehall II study, which is looking at the association of social, behavioural and biological factors on long-term health. All were aged 35 to 55 and free of dementia when they joined the study between 1985 and 1988.

For this study multimorbidity was defined as the presence of at least two chronic conditions from a predefined list of 13 types, including heart disease, high blood pressure, diabetes, heart failure, depression, liver disease, stroke, arthritis and cancer.

The research, published in the British Medical Journal, found that the risk of dementia was greater when these sorts of conditions developed at a younger age (mid-50s) rather than later in life.

For those with three or more chronic conditions at 55 there was a fivefold higher risk of dementia

For every five years younger a person was when multimorbidity occurred up to the age 70 the risk of dementia went up by 18 per cent.

From the group of Britons taking part in the Whitehall II study, 7 per cent had two or more conditions aged 55, rising to 32 per cent at age 70. Overall, 639 cases of dementia occurred over an average 32-year follow-up.

After adjusting for factors such as socioeconomic status, diet and lifestyle, having two or more conditions aged 55 pushed up the risk of dementia almost 2.5 times compared with people who had none. Developing two or more conditions between 60 and 65 was associated with a 1.5-fold higher risk.

For those with three or more chronic conditions at 55 there was a fivefold higher risk of dementia. The risk fell dramatically if people were aged 70 before they developed chronic health conditions.

“Given the lack of effective treatment for dementia and its personal and societal implications, finding targets for prevention of dementia is imperative,” the researchers wrote. “These findings highlight the role of prevention and management of chronic diseases over the course of adulthood to mitigate adverse outcomes in old age.”

Prof Paul Morgan of the Dementia Research Institute at Cardiff University, who was not involved in the research, described the work as a "landmark study" which he said concluded that the number of chronic health conditions and how long a person had them was "strongly predictive" of dementia risk. – Guardian