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Original research
Glucose metabolism in midlife predicts participation in working life: a Northern Finland Birth Cohort 1966 study
  1. Tuulia Varanka-Ruuska1,2,
  2. Mimmi Tolvanen1,
  3. Eeva Vaaramo3,
  4. Sirkka Keinänen-Kiukaanniemi1,4,
  5. Sylvain Sebert1,5,
  6. Nina Rautio1,
  7. Leena Ala-Mursula1
  1. 1 Center for Life Course Health Research, University of Oulu, Oulu, Finland
  2. 2 Kallio Primary Health Care Unit, Ylivieska, Finland
  3. 3 Infrastructure for Population Studies, Faculty of Medicine, University of Oulu, Oulu, Finland
  4. 4 Healthcare and Social Services of Selänne, Pyhäjärvi, Finland
  5. 5 MRC-PHE Centre for Environment and Health, Imperial College London, London, UK
  1. Correspondence to Tuulia Varanka-Ruuska, Center for Life Course Health Research, University of Oulu, Oulu 90014, Finland; tuulia.varanka-ruuska{at}


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.

  • type 2 diabetes
  • longitudinal cohort study
  • register study
  • unemployment
  • Disability

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  • Contributors TV-R, NR, SS and LA-M conceived the research question and drafted the study design. MT, EV and SK-K contributed to the study design. EV acquired the data for the registered variables. TV-R and MT performed the statistical analyses. TV-R wrote the first draft of the manuscript. All the authors contributed to the interpretation of the results, revised the manuscript critically and approved the final version before submission. LA-M is the guarantor of the study.

  • Funding This project has received funding form European Regional Development Fund (539/2010 A31592), European Union’s Horizon 2020 research and innovation program (633595), Oulu University Hospital (24301140) and University of Oulu (24000692).

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval The Ethics Committee of Northern Finland Hospital District approved the study.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available on reasonable request. Data are available from the Northern Finland Birth Cohort (NFBC) for researchers who meet the criteria for accessing confidential data. Please, contact NFBC project center ( and visit the cohort website ( for more information.