BACKGROUND:

Little is known about the relationship between polypharmacy and Parkinson's disease (PD). In the present study, we tested the hypothesis that polypharmacy increases the risk of PD in older people in Taiwan.

METHODS:

From a randomly sampled cohort of one million health insurance enrollees, we identified 2827 new cases of PD over the period 2000-2008 aged ≥ 65 years and selected 11 308 age-matched controls without PD. Medication history and baseline comorbidities were compared between the two groups. We defined 'polypharmacy' as an average daily use of five or more prescribed drugs.

RESULTS:

Compared with patients using between none and one drug, the odds ratios (ORs) for PD increased to 1.53, 2.08, 2.64, and 2.95 for patients using two to four, five to seven, eight to nine, and ≥ 10 drugs, respectively. The other conditions associated with PD were dementia (OR 3.43), stroke (OR 2.30), depression (OR 2.15), and alcoholism (OR 2.11). Hyperlipidemia (OR 0.90) was inversely associated with PD.

CONCLUSIONS:

Polypharmacy was shown to increase the risk of PD in older people in Taiwan, with risk increasing with the number of medications taken daily. Dementia, stroke, depression, and alcoholism were also associated with an increased risk of PD, whereas there was an inverse correlation between PD and hyperlipidemia.