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.

Keywords: Cardiovascular Disease; Drug Therapy; EPIDEMIOLOGIC STUDIES; EPIDEMIOLOGY; Risk Factors.

Figure 1. Flowchart of the participants. The Tromsø study 1994–2016. LLDs, lipid-lowering drug

Figure 2. Observed estimated mean longitudinal cholesterol (mmol/L) in women and men over surveys and education among non-user of lipid-lowering drugs (LLD) (A and B) and user of lipid-lowering drugs from 2001 (Tromsø5) to 2015–2016 (Tromsø7) (C and D). The Tromsø Study 1994–2016.