Geographical differences in the prevalence of chronic polypharmacy in older people: Eleven years of the EPIFARM-Elderly Project

Purpose: To compare the geographical differences in the prevalence of chronic polypharmacy in community-dwelling older people over 11 years. Methods: This study analyzed nearly two million patients aged 65-94 years recorded in the Drug Administrative Database of the Lombardy Region (Northern Italy) from 2000 to 2010. Chronic polypharmacy was defined as taking five or more drugs in 1 month for at least 6 months (consecutive or not) in a year. Results: There was a significant spatial autocorrelation that increased at the municipality level from 2000 (Moran's I Index = 0.26, z score = 16.91, p <0.0001) to 2010 (Moran's I Index = 0.36, z score = 23.78, p <0.0001). Clusters of high (Z(G) > 1.96) and low (Z(G) <-1.96) prevalence rates of chronic polypharmacy were found and were not influenced by age. Chronic polypharmacy weakly correlated with hospital admission (2000: ρ = 0.08, p = 0.0032; 2005: ρ = 0.11, p <0.0001; 2010: ρ = 0.18, p <0.0001), but not with mortality. Conclusions: There were geographical differences in the prevalence of older people with chronic polypharmacy that were only partly explained by health indicators. Targeted activities on prescription practice to ensure that the prescribing of chronic polypharmacy is appropriate are required.