Glucose metabolism in midlife predicts participation in working life: a Northern Finland Birth Cohort 1966 study.

Objective: To evaluate how clinically measured glucose metabolism categories predict registered participation in working life.

Methods: In the 46-year follow-up of Northern Finland Birth Cohort 1966 (n=5328, 2342 men and 2986 women), we used oral glucose tolerance tests, surveys and glycated haemoglobin to determine glucose metabolism categorised as normal, pre-diabetes, screen-detected and previous type 2 diabetes (T2D). Consequent participation in working life during the 2-year follow-up period was measured as registered disability, unemployment and employment days, for which incidence rate ratios (IRRs) with 95% CIs were calculated using Poisson regression, adjusted for baseline employment and socioeconomic, health-related and behavioural factors.

Results: In comparison to normal glucose, all categories of impaired glucose metabolism were associated with poorer participation in working life in the unadjusted models. After adjustments, the risks (IRR (95% CI)) of disability days remained heightened by both screen-detected and previous T2D among men (1.3 (1.3 to 1.4) and 1.5 (1.4 to 1.5), respectively), whereas among women the risks were lowered (0.9 (0.8 to 0.9) and 0.9 (0.9 to 1.0), respectively). The risks of unemployment were consistently higher in all categories of impaired glucose metabolism, and were the highest among women with previous T2D (1.6 (1.5 to 1.6)). Correspondingly, the rates of total employment days were lower in relation to screen-detected T2D among men and women (5% and 6%, respectively), and previous T2D (6% and 3%).

Conclusions: Overall, impaired glucose metabolism associated with deteriorated working life participation already in middle age. The high prevalence of impaired glucose metabolism emphasises the need for actions to support sustainable working careers.