Knowledge of social inequalities in monoclonal gammopathy of undetermined significance (MGUS) will contribute to understanding multiple myeloma (MM) etiology, as MGUS consistently precedes MM. The aim of the present study was to examine whether socioeconomic position (SEP) is associated with MGUS in a population-based cohort including information on potential MGUS risk factors. Overall, 4787 study participants aged 45-75 years with information on MGUS were included. SEP indicators (education, income) and potential risk factors (i.e., body mass index, diabetes, smoking, dietary factors) were assessed at baseline. Overall, 260 MGUS cases were detected at baseline and prospectively over a 10-year follow-up. In age-adjusted logistic regression models, a lower chance of having MGUS at baseline or developing MGUS during 10 years of follow-up was indicated for groups of low SEP with odds ratios (OR) of 0.39 (95% confidence interval [95%-CI] 0.19-0.76) for women and 0.48 (95% CI 0.10-1.16) for men in the lowest compared to the highest educational group. After additionally including potential mediating risk factors in the regression models, the estimated ORs changed only slightly in magnitude. Similar results were obtained for income. Current smoking and low fruit consumption were associated with MGUS independently of SEP in women, but not in men. The present study indicates a lower MGUS risk in lower SEP groups. Supporting evidence is given that smoking and diet play a role in the development of MGUS independently of SEP, while it has to be assumed that risk factors unknown to date are responsible for the observed social inequalities in MGUS.
Keywords: Health inequalities; MGUS; Monoclonal gammopathy of undetermined significance; Multiple myeloma; Socioeconomic position.