Do socioeconomic disparities affect assessing and keeping antihypertensive drug therapy? Evidence from an Italian population-based study

We conducted this population-based cohort study by linking several databases to explore the role of socioeconomic position for accessing and keeping antihypertensive drug therapy. A total of 71469 patients, residents in the city of Milan (Italy) aged 40-80 years, who received an antihypertensive drug during 1999-2002 were followed for 1 year starting from the first dispensation. Socioeconomic position and drug prescriptions were respectively obtained from tax registry and outpatient prescription database. The effect of socioeconomic characteristics on standardized incidence rate (SIR) of new users of antihypertensive agents, odds ratio (OR) of using combined antihypertensive agents and non-antihypertensive drugs and hazard ratio (HR) of discontinuing antihypertensive therapy were estimated after adjustment for potential confounders. SIRs were 3.7 and 4.2 per 1000 person-months among persons at the lowest and intermediate income, respectively, and 2.4 and 3.0 among immigrants and Italians, respectively. Compared to persons at the highest income, those at the lowest income had increased chances of starting with combined antihypertensive drugs (OR: 1.1; 95% confidence intervals (CIs): 1.0, 1.2), and of using drugs for heart failure (OR:1.5; CIs:1.3, 1.6) and diabetes (OR: 1.7; CIs: 1.6, 1.9). Compared with Italians, non-western immigrants had increased chances of starting with combined antihypertensive agents (OR: 1.2; CIs: 1.0, 1.3), of using drugs for heart failure (OR: 1.2; CIs: 1.0, 1.4) and for diabetes (OR: 1.8; CIs: 1.6, 2.1), and of interrupting antihypertensive therapy (HR: 1.1; 95% CIs: 1.0, 1.2). Despite the universal health coverage of the Italian National Health Service (NHS), social disparities affect accessing and keeping antihypertensive therapy.