Association of Polypharmacy With Mild Cognitive Impairment and Cognitive Ability: A Nationwide Survey in Taiwan

Background: Polypharmacy, defined as the concomitant use of 5 or more medications, has a documented negative association with cognitive impairment such as delirium and is associated, potentially, with a higher risk of dementia. However, whether polypharmacy contributes to increased risk of mild cognitive impairment (MCI) or decreased cognitive capacity requires further investigation. This nationwide population survey investigated the association among polypharmacy, MCI, and dementia. Methods: Through random sampling based on the proportion of all Taiwan counties, subjects were recruited and received in-person interviews between December 2011 and March 2013. Demographic data and clinical information included medical histories, medication use, and mental status measured by the Taiwanese Mini-Mental State Examination (TMSE) and Clinical Dementia Rating (CDR). Data on lifestyle and habits were collected, and subjects were distributed to cognitively normal, MCI, or all-cause dementia groups based on criteria by the National Institute on Aging and the Alzheimer's Association. Results: A total of 7,422 people aged 65 years or older were recruited. After adjustment for age, sex, body mass index, education, medical comorbidities, and lifestyle and habits, polypharmacy was associated with a 1.75-fold increased odds of MCI and 2.33-fold increased odds of dementia. Polypharmacy was associated with a 0.51-point decrease in TMSE scores (P=.001) and a 0.10-point increase in CDR score (P<.001). Additionally, for those without specific vascular comorbidities, polypharmacy had a greatly more negative impact on cognitive capacity. Conclusions: Polypharmacy is common in the elderly and is associated with significantly lower cognitive capacity and higher risks of MCI and dementia, especially for persons without diabetes, hypertension, hyperlipidemia, or cerebrovascular diseases.