Do statins reduce hospital admissions for cardiovascular diseases?

Managing cardiovascular risk is a major concern for healthcare systems. Statins are lipid-lowering drugs used to prevent adverse cardiovascular events. Using an instrumental variables approach, this study provides district-level evidence consistent with a causal effect of statin prescribing on hospitalisation rates for cardiovascular disease. By exploiting variation in prescribing patterns and physicians' preferences to construct an instrument for district-level statin consumption, we move beyond the correlational evidence from existing ecological studies. We focus on the Emilia-Romagna region (Italy) from 2010 to 2019, using district-level longitudinal data. We consider two study populations to measure hospitalisations among individuals aged 50 and over: firstly, the general population living in the region; secondly, those on statin therapy (statin users). The IV estimates show that increasing statin use at the district level is linked to reduced cardiovascular hospitalisation rates, with effects varying by diagnosis and type of admission. Comparing district-level measures of coverage and average treatment intensity, we find more consistent evidence for the coverage-based specification, while intensity estimates based on DDDs per treated patient are less stable and require cautious interpretation. Exploratory analyses by recent hospitalised vascular-event history suggest some differences across treated users, but formal tests provide limited evidence of statistically significant heterogeneity. Overall, the findings support population-level pharmaceutical prevention while cautioning against interpreting aggregate coverage-intensity margins as clean individual-level mechanisms.