The onset of multimorbidity earlier in life was associated with an increased risk for subsequent dementia, according to results of a prospective cohort study, published in the British Medical Journal.
As life expectancy has continued to increase, the prevalence of dementia has been on the rise. Alzheimer disease is the primary cause of dementia and is a complex, multisystemic disease of which the causes and effective treatments remain elusive. The objective of the current study was to examine the association of midlife and late life multimorbidity, including multimorbidity severity, with the risk of developing dementia.
To explore the potential role of multimorbidity in dementia, data for this study were sourced from the ongoing Whitehall II cohort study. Between 1985 and 1988, British civil service employees (N=10,095) were recruited for a longitudinal study. Linked patient data from the National Health Service (NHS) for study participants has been updated annually until 2019. Risk for dementia was assessed on the basis of multimorbidity status which was defined as 2 or more chronic conditions out of a predefined list of 13 conditions.
As of 2019, 639 participants had been diagnosed with dementia. The dementia and control cohorts were 58.5% and 67.9% men, aged mean 49.9 (standard deviation [SD], 4.9) and 44.6 (SD, 6.0) years at baseline, 59.2% and 46.5% had low secondary school or lower education, and 70.4% and 50.9% had multimorbidity, respectively.
At age 55 years, 6.6% of the population had multimorbidity and by 70 years of age, 31.7% had developed multimorbidity.
Dementia risk was increased among individuals with diabetes (hazard ratio [HR], 2.31) and hypertension (HR, 1.37) at age 55 years; mental disorders (HR, 13.51), stroke (HR, 3.55), diabetes (HR, 2.21), depression (HR, 1.71), coronary heart disease (HR, 1.46), and hypertension (HR, 1.29) at age 60 years; Parkinson disease (PD) (HR, 21.24), mental disorder (HR, 6.66), chronic obstructive pulmonary disease (HR, 3.64), heart failure (HR, 3.44), stroke (HR, 2.68), diabetes (HR, 1.98), depression (HR, 1.79), coronary heart disease (HR, 1.31), and hypertension (HR, 1.29) at age 65 years; and PD (HR, 19.31), chronic kidney disease (HR, 5.18), depression (HR, 1.93), diabetes (HR, 1.60), and hypertension (HR, 1.31) at age 70 years.
Dementia onset at ages 60, 65, or 70 years was associated with the onset of multimorbidity before 55 years of age (adjusted hazard ratio [aHR] range, 2.46-2.60; P <.001).
The risk for dementia was highest among individuals with 3 or more chronic conditions by 55 years of age (aHR, 4.96; 95% CI, 2.54-9.67), followed by 3 or more chronic conditions by 60 years of age (aHR, 4.23; 95% CI, 2.84-6.31), and 3 or more chronic conditions overall (aHR, 3.29; 95% CI, 2.70-4.01).
As data for this study was extracted from linked health records, there is the possibility that some patient information was missing or incorrect. In addition, the study population was not diverse, so these findings may not be generalizable.
“Multimorbidity, particularly when onset is in midlife rather than late life, has a robust association with subsequent dementia,” the researchers concluded.
Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.
Hassen CB, Fayosse A, Landré B, et al. Association between age at onset of multimorbidity and incidence of dementia: 30 year follow-up in Whitehall II prospective cohort study. BMJ. Published online February 2, 2022. doi:10.1136/bmj-2021-068005