Educational inequalities in midlife risk factors for non-communicable diseases in two Norwegian counties 1974–2002

Background: The absolute educational differences in the mortality of Norwegian women and men increased during 1960–2000 and thereafter levelled off in men, but continued to widen in women. Which of the risk factors for non-communicable diseases (NCDs) might explain these trends? Aim: The aim of this study was to investigate trends in gender-specific, absolute educational differences in established risk factors during 1974–2002. Methods: We used cross-sectional data from 40–45-year-old women and men who participated in one of three health surveys in two counties, from the years 1974–1978, 1985–1988 and 2001–2002. To account for increasing educational attainment through the period we used a regression-based index of inequality (Slope Index of Inequality) to assess the educational gradients over time. Results: From 1974 to 2002, the mean levels of serum total cholesterol and blood pressure decreased and body mass index (BMI) increased in all subgroups by education in both sexes. In men, the educational gradient tended to diminish toward the null for serum total cholesterol and narrowed for systolic blood pressure, but increased for BMI. In women, the educational gradient increased to the double for smoking and increased for triglycerides. Conclusions: In two Norwegian counties, the NCD risk factors showed dynamic patterns during 1974–2002. For blood pressure and serum total cholesterol, the levels showed consistent beneficial changes in all educational subgroups, with a narrowing tendency for educational gradients in men. In women, the educational gradient for smoking increased markedly. Knowledge on midlife trends in the educational gradients of risk factors may help to explain recent and future NCD mortality.