Longitudinal cholesterol trends across socioeconomic groups in Norway: the influence of lipid-lowering drugs in the population-based Tromsø Study 1994–2016

Abstract

Objectives There is limited evidence regarding the impact of lipid-lowering drugs (LLDs) on the socioeconomic gradient in a longitudinal perspective. The study investigates the longitudinal socioeconomic gradient in total cholesterol levels and whether this is affected by the use of LLDs.Design Population-based cohort study.Setting Sample from adult inhabitants of Tromsø municipality, Norway, who participated in the Tromsø Study (1994–2016).Participants 17 550 participants of the population-based Tromsø Study in 1994–1995 who were non-users of LLD, aged 25–78 years at baseline and who attended one or more of three subsequent surveys in 2001, 2007–2008 and 2015–2016 were included in the study.Outcome measure Socioeconomic gradient in total cholesterol levels was compared among participants treated and not treated with LLDs during the observation period.Results The total cholesterol levels across all educational groups increased from 1994–1995 to 2015–2016 among untreated women (+0.33 mmol/L to +0.48 mmol/L), except for those with primary education (−0.12 mmol/L). Total cholesterol levels decreased among untreated men (−0.40 mmol/L to −0.06 mmol/L, from lowest education to highest education), treated women (−1.88 mmol/L to −1.35 mmol/L) and men (−2.21 mmol/L to −1.84 mmol/L) across all educational groups. At baseline, we observed a significant inverse association between education and total cholesterol levels among non-users of LLDs. There was no clear educational gradient in total cholesterol levels among users of LLDs.Conclusions Users of LLDs experienced a more substantial decrease in total cholesterol levels over time compared with non-users. The educational gradient in total cholesterol levels observed among non-users of LLD was not apparent among users.