Study Suggests Multimorbidity Associated with Increased Dementia Risk

Catherine M. Calvin, PhD

A recent study found that mulimorbitity was associated with increased dementia risk, potentially helping clinicians to identify those at high risk of the condition.

The prevalence of this condition has increased as a result of global life expectancy, which is why the study was created and led by Catherine M. Calvin, PhD, and Thomas J. Littlejohns, PhD, of the Nuffield Department of Population Health at the University of Oxford. Around two-thirds of people ages 65 to 84 live with multimorbidity, a condition involving 2 or more long-term health issues.

“To our knowledge, 2 studies have investigated the association between multimorbidity and dementia risk,” Calvin and colleagues wrote. “Both found that multimorbidity was associated with an increased risk of dementia, while one found that neuropsychiatric, cardiovascular, and sensory impairment or cancer clusters, but not a respiratory, metabolic, and musculoskeletal cluster, were associated with an increased risk.”

Research and Background

The investigators designed a population-based prospective cohort study with data gathered between 2006 and 2010 from the UK Biobank cohort. Study participants were 60 years or older and did not report dementia, with this data gathered from interviews with nurses at 1 of the 22 baseline assessment centers in England, Scotland or Wales.

The final sample size in the participant population was 206,960. During the nurse’s interviews at the assessment centers, participants reported their medical conditions. The researchers defined multimorbidity as having at least 2 out of 42 listed conditions, and those with dementia prior to baseline were excluded.

The investigators assessed dementia information using hospital death registry and inpatient records. They also collected sociodemographic information such as sex, age, ethnicity, education and socioeconomic status. This information was collected due to the wide variance observed between ethnic groups on dementia risk and multimorbidity.

Study Findings

The investigators found that about 43% (89,201) of the study’s 206,960 participants were reported as having multimorbidity, with the mean age being 64.1 years. About 3% (6,182) of participants were found to have developed dementia over a mean of 11.8 years of follow-up.

Incidence rates for dementia were 3.41 per 1000 person-years (95% CI, 3.30 - 3.53) with multimorbidity compared to 1.87 per 1000 without (95% CI, 1.80 - 1.94). The research team also found that 52.7% of the final sample of 206,960 study participants were female, though there was no statistically significant interaction with regard to sex, ethnicity, age, socioeconomic status, or education.

“Various disease clusters were differentially associated with dementia risk, with hypertension, diabetes, and CHD and pain, osteoporosis, and dyspepsia clusters in women and diabetes and hypertension and CHD, hypertension, and stroke clusters in men associated with double or more the risk of dementia,” they wrote.

Furthermore, the investigators identified a statistically significant interaction of APOE genotype with dementia risk and multimorbidity, identifying stronger associations with noncarriers. They added that APOE-ε4 allele’s presence has led to a fourth of heritability for Alzheimer disease, dementia’s most common form.

The investigators hoped to help clinicians identify those with high risk of dementia as well as to stress the importance of targeting disease clusters for dementia, as opposed to individual risk factors.

This study, “Association of Multimorbidity, Disease Clusters, and Modification by Genetic Factors With Risk of Dementia,” was published online on JAMA Network Open.