Chronic Conditions linked to Dementia Risk

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Chronic Conditions linked to Dementia Risk

Jim Windell

           As life expectancy has increased over the past couple of centuries, there is a downside to living longer.

           While adults, particularly in high income countries, commonly life to age 65 and beyond, this longevity comes with the growing prevalence of dementia. Typically, dementia increases markedly after age 65. The primary cause of dementia is Alzheimer's disease, which is a complex, multisystemic disease for which an effective cure remains elusive.

           As research on the causes and treatments for Alzheimer’s proceeds, there is increasing interest in how risk factors over the life course, including chronic diseases, shape the risk of dementia at older ages. That interest has resulted in better understanding multimorbidity, usually defined as the presence of two or more chronic diseases irrespective of the severity of such conditions. Some recent estimates suggest that more than 50% of older adults in high income countries report multiple chronic conditions.

           What has been found in older adults with dementia is the presence of several comorbid conditions. In fact, at least one study found higher risk of dementia in those with multimorbidity. But, up to now, there has been no long-term study assessing the dementia risk in those with multiple chronic conditions. But a new study, recently published in the British Medical Journal,  has followed people for an average of 32 years.

           To conduct the study several researchers drew on data from 10,095 people who took part in the Whitehall II study. This study tracked British civil servants for an average of 32 years, starting between 1985 and 1988.

           The researchers knew at the beginning of the study that multimorbidity is common, particularly at older ages and in people living with dementia. But studies examining whether multimorbidity at earlier ages affects the risk of subsequent dementia were lacking. To fill this knowledge gap, researchers set out to examine the long-term association between multimorbidity at ages 55, 60, 65, and 70 and subsequent dementia.

           According to Dr. Archana Singh-Manoux, a research professor at the Université de Paris in France and the corresponding author of the new study, “Multimorbidity — the occurrence of two or more chronic diseases — is increasingly common and not confined to older ages. It is also associated with a range of adverse health outcomes, including mortality. There is quite a lot of evidence showing some chronic diseases — analyzed one at a time — are associated with dementia, leading us to examine the role of multimorbidity in the risk of dementia.”

           The results of the research confirm that having two or more chronic conditions in middle age is associated with an increased risk of dementia later in life. These common chronic conditions include high blood pressure, diabetes, coronary heart disease, depression, and chronic lung disease (COPD). The risk for dementia is greater when these sorts of conditions develop at a younger age (mid-50s) rather than later in life. 

           After taking into account a range of factors, including age, sex, ethnicity, education, diet and lifestyle behaviors, multimorbidity at age 55 was associated with a 2.4-fold higher risk of dementia compared with people without any of the 13 chronic conditions. On the other hand, those with three or more chronic conditions at age 55 had a nearly five-fold higher risk of dementia, whereas the risk was 1.7-fold higher when onset of multimorbidity was at age 70. 

           Since this was an observational study, cause cannot be established. And the researchers point to some limitations in the study – such as possible misclassification of some dementia cases, and the fact that study participants are likely to be healthier than the general population.

           However, this was a large study with over 30 years of follow-up, and results were similar after further analyses using death as the outcome measure, which the researchers say increases confidence in their findings on dementia.

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

           To read the original article, find it with this reference:

Ben Hassen, C., Fayosse, A., Landr,Ã,B., Raggi, M., Bloomberg, M., Sabia, S. et al. (2022). Association between age at onset of multimorbidity and incidence of dementia: 30 year follow-up in Whitehall II prospective cohort study. The British Medical Journal, 376 :e068005 doi:10.1136/bmj-2021-068005


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