Associations of educational level with ECG-derived cardiovascular ageing in a population-based cohort: a mediation analysis from the Tromsø Study.

OBJECTIVE

To assess the association between educational level and cardiovascular age acceleration metric derived from ECG, and to determine whether this association is mediated by established cardiovascular disease (CVD) risk factors.

DESIGN

Prospective population-based cohort study (the Tromsø Study).

SETTING

General population of the Tromsø municipality, Norway.

PARTICIPANTS

The study sample consisted of 4367 participants of the Tromsø Study, who took part in both Tromsø6 (2007-2008) and Tromsø7 (2015-2016), had a 12-lead ECG obtained at Tromsø7 and did not report a history of heart attack, stroke or atrial fibrillation.

PRIMARY OUTCOME MEASURES

δ-age, a biomarker of cardiovascular ageing, is defined as the difference (in years) between an individual's ECG-predicted heart age and their chronological age. ECG-predicted heart age was estimated using a previously validated deep neural network.

RESULTS

Our findings indicate an inverse association between education and δ-age, with a regression coefficient per increment increase in education of -0.24 (95% CI -0.41 to -0.07) in the overall sample, -0.38 (95% CI -0.59 to -0.16) for women and -0.04 (95% CI -0.31 to 0.23) for men. Participants with the highest level of education (university/college for 4 or more years) had the lowest estimated δ-age with a regression coefficient of -0.69 years (95% CI -1.23 to -0.16) compared with the group with primary education for the overall sample, -1.05 years (95% CI -1.73 to -0.37) for women and -0.15 years (95% CI -1.03 to 0.73) for men. CVD risk factors mediated up to 75% of the association between overall education and δ-age, and 80% of the association among those with the highest education level (university/college for 4 or more years). Among women, 50% of the effect of overall education on δ-age was mediated by CVD risk factors, rising to 53% in the category with the highest level of education. However, in the subsample of men, there was no significant association between education and δ-age, and the mediation analysis produced natural direct and indirect effects pointing in opposite directions.

CONCLUSIONS

Cardiovascular ageing is inversely associated with educational level, an effect that appears to be largely mediated through established risk factors.