AIM:

The aim of the present study was to investigate whether polypharmacy correlates with the risk of dementia in older people.

METHODS:

From representative claims data established from the National Health Insurance with a population coverage rate of 99% in Taiwan, we identified 7135 newly diagnosed patients with dementia in 2000-2008 and 2,8540 randomly selected controls without dementia, both aged ≥ 65 years. The daily use of prescribed drugs in the past 2 years was compared between cases and controls, controlling for demographic characters and comorbidities.

RESULTS:

The incidence of dementia increased with the number of medications used and age. Cases were older than controls, predominant with women and more likely to use five or more drugs daily (44.0% vs 32.0%, P < 0.0001). Multivariate logistic regression analysis showed that, compared with participants using zero to one drug, the odds ratios (OR) of dementia were 1.28 (95% confidence interval [CI] 1.18-1.38) for those using two to four drugs, 1.34 (95% CI 1.23-1.46) for those using five to nine drugs and 1.56 (95% CI 1.38-1.76) for those using 10 or more drugs. Cerebrovascular disease (OR 3.19), diabetes mellitus (OR 1.23), chronic kidney disease (OR 1.21) and hypertension (OR 1.08) were significant comorbidities predicting the risk of dementia. There was significant interaction between cerebrovascular disease and the number of medications used in the dementia risk.

CONCLUSIONS:

The risk of dementia increases steadily with the number of medications used and age in older people in Taiwan. Cerebrovascular disease, diabetes mellitus, chronic kidney disease and hypertension might also correlate with the risk of dementia.