Multimorbidity associated with increased risk for dementia
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Adults with two or more chronic conditions by middle age had an increased risk for dementia later in life, according to findings published in The BMJ.
“Given the lack of effective treatment for dementia and its personal and societal implications, finding targets for prevention of dementia is imperative,” Céline Ben Hassen, of the department of epidemiology of aging and neurodegenerative diseases at the University of Paris, and colleagues wrote. “Multimorbidity is increasingly prevalent, starting in early adulthood and midlife.”
Hassen and colleagues examined the association of midlife and late-life multimorbidity with incident dementia using data from the prospective cohort Whitehall study. The cohort included 10,095 participants who were employees of the British civil service. They were aged 35 to 55 years at baseline, which was from 1985 to 1988. They received follow-up clinical examinations every 4 to 5 years. The participants’ data were linked to electronic health records through the U.K. National Health System and were updated annually up to March 31, 2019.
The researchers defined multimorbidity as the presence of two or more chronic conditions. They evaluated the participants for 13 common chronic conditions, including coronary heart disease, stroke, heart failure, diabetes, hypertension, cancer, chronic kidney disease, chronic obstructive pulmonary disease, liver disease, depression, mental disorders other than depression, Parkinson’s disease and arthritis/rheumatoid arthritis.
Incidence of dementia
By March 2019, after a median follow-up of 31.7 years, 639 cases of dementia were documented. Among those with dementia, 58.5% were men, 85.6% were white and the mean age was 49.9 years, according to Hassen and colleagues.
Overall, 63% of participants aged 55 years had no chronic disease compared with 29.8% of participants aged 70 years.
Multimorbidity and risk for dementia
The researchers reported that 6.6% of participants aged 55 years and 31.7% of those aged 70 years had multimorbidity. After adjustment for sociodemographic factors and health behaviors, multimorbidity among those aged 55 years was associated with a higher risk for dementia later in life, with a difference in incidence rate of 1.56 (95% CI, 0.62-2.77) per 1,000 person-years (HR = 2.44; 95% CI, 1.82-3.26). However, the risk association weakened progressively with older age at onset of multimorbidity. For example, by age 65 years, the onset of multimorbidity before age 55 years was associated with 3.86 (95% CI, 1.8-6.52) per 1,000 person-years higher incidence of dementia (HR = 2.46; 95% CI, 1.8-2.26), and onset between age 60 and 65 years was associated with 1.85 (95% CI, 0.64-3.39) per 1,000 person-years higher incidence (HR = 1.51; 95% CI, 1.16-1.97) of dementia. Severity of multimorbidity, defined as having three or more chronic conditions, for those aged 55 years was associated with a 5.22 (95% CI, 1.14-11.95) per 1,000 person-years higher incidence of dementia (HR = 4.96; 95% CI, 2.54-9.67), according to Hassen and colleagues. Moreover, severe multimorbidity among those aged 55 years was associated with a 4.49 (95% CI, 2.33-7.19) per 1,000 person-years higher incidence (HR = 1.65; 95% CI, 1.25-2.18) of dementia by age 70 years.
Chronic conditions
Hassen and colleagues reported that the most common chronic conditions among participants with dementia were hypertension (77.9%), coronary heart disease (27.7%), depression (27.2%) and diabetes (24.7%). The prevalence of all individual chronic conditions increased with age, yet some conditions, like diabetes, showed a steady increase during the study period and others, like chronic obstructive pulmonary disease and chronic kidney disease, showed a more rapid increase between those aged 65 and 70 years. The researchers reported that Parkinson’s disease had the strongest association with incident dementia (HR = 8.16; 95% CI, 5.68-11.73) in time-carrying analyses. Also, mental disorders had a strong association at age 60 years (HR = 13.51; 95% CI, 6.53-27.95). However, it decreased by age 70 years (HR = 2.05; 95% CI, 0.97-4.35).
“Our results show that multimorbidity is associated with an increased risk of dementia at older ages, even more so when onset of multimorbidity is in midlife rather than late life,” Hassen and colleagues 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.”
Perspective
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Margot Savoy, MD, MPH, FAAFP
[This study and additional research] confirm a looming concern many family physicians have held as we have seen the dramatic rise in chronic, comorbid conditions at younger ages. The cumulative effect of CVDs such as hypertension, hyperlipidemia and diabetes have long been culprits at causing cognitive decline. It doesn’t seem a stretch to imagine that other chronic conditions such as liver, lung and kidney disease and the treatments needed to manage them could have long-lasting cognitive impact as well.
These types of findings elicit two groups of questions for me. First, I question, what does it really mean? For example, if these findings are not due to diet, exercise or lifestyle, could there be some underlying genetic issue that puts people at risk for chronic disease in general, and that happens to include dementia? Is this some other cross-linking impact of multimorbidity such as polypharmacy or even an environmental impact that could be tied to industry or exposure? Second, I wonder which prevention interventions could reduce or eliminate these chronic conditions and possibly reduce the downstream dementia.
Currently, we don’t adequately fund prevention in the U.S. Ensuring access to healthy foods, including fresh fruits and vegetables, reducing environmental toxins such as lead, providing safe spaces for exercise and treatments are just the tip of the work we could be doing to reframe medical care as true health care — seeking opportunities to make health and wellness the goal rather than simply managing disease. Benjamin Franklin was speaking about fire prevention in Philadelphia back in 1736 when he said, “An ounce of prevention is worth a pound of cure.” That adage remains true today. Preventing disease is healthier, easier and cheaper than trying to cure it.
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