Multimorbidity associated with increased risk for dementia

Multimorbidity was associated with a 63% increased risk for incident dementia, with the greatest risk linked to hypertension and diabetes, researchers reported in JAMA Network Open.

The global prevalence of dementia is projected to increase from 57 million to 153 million individuals by 2050 — a threefold increase, Catherine M. Calvin, PhD, of the department of population health at Oxford University, and colleagues wrote.

Calvin and colleagues conducted a population-based, prospective cohort study to assess whether multimorbidity was associated with incident dementia and whether associations varied by different disease clusters and genetic risk.

The researchers used data from the UK Biobank cohort, which included baseline information collected between 2006 and 2010 and up to 15 years of follow-up. Participants included individuals aged 60 years and older without dementia at baseline. Medical conditions were recorded through verbal interviews at baseline.

The authors defined multimorbidity as the presence of at least two long-term conditions from a preselected list of 42 conditions. Genetic risk was based on the presence of one or two apolipoprotein e4 alleles (APOE), and incident dementia was identified using hospital inpatient and death registry records. Associations of multimorbidity with dementia were assessed with Cox proportional hazard models.

A total of 206,960 participants (mean age, 64 years; 52.7% women) were included in the final sample. Of those, 89,201 people (43.1%) had multimorbidity. Over a mean of 11.8 years, 6,182 participants (3%) developed dementia.

The incident rate of dementia was 1.87 per 1,000 person-years for those without multimorbidity (95% CI, 1.8-1.94). For those with multimorbidity, the rate was 3.41 (95% CI, 3.3-3.53).

After adjusting for age, sex, ethnicity, education, socioeconomic status and APOE carrier status, researchers reported that multimorbidity was associated with an increased risk for incident dementia (HR = 1.63; 95% CI, 1.55-1.71).

The highest dementia risk was reported in women with hypertension, diabetes and coronary heart disease (HR = 2.2; 95% CI, 1.98-2.46) and in men with hypertension and diabetes (HR = 2.24; 95% CI, 1.97-2.55). Associations between multimorbidity and dementia were greater in those with a lower genetic risk for dementia (HR = 1.96; 95% CI, 1.81-2.11) compared with those with a higher genetic risk for dementia (HR = 1.39; 95% CI, 1.3-1.49).

“Overall, these findings could improve identification of individuals at high risk of dementia and highlight the necessity of targeting clusters of diseases for dementia prevention rather than individual risk factors,” the authors wrote.