Objectives The Norwegian Agreement on a More Inclusive Working Life (the IW Agreement) was introduced in 2001 amid efforts to reduce sickness absence (SA) and increase work participation. Little research has been done on the effects of this agreement. The study’s aim was to compare SA before and after introduction of the IW Agreement.

Methods Data from several national registries involving 115,119 individuals born in Norway 1967–1976 was used. Individuals were classified using ICPC-2 codes into musculoskeletal (code L) and mental health (code P) diagnosis groups. A difference-in-differences method using logistic regression was used to compare the difference in one year risk of SA lasting >16 days in individuals working in IW companies relative to non-IW companies in 2000 and 2005. Analyses were adjusted for age, gender, and industry. Standard errors were clustered at the individual level and average marginal effects were calculated with 95% confidence intervals. Gender and industry specific models were also estimated.

Results There was no significant association between the IW Agreement and risk of SA in the overall musculoskeletal diagnosis group (-0.4 percentage points (PP), CI -0.9,0.1), but women had significantly lower risk of SA (-0.8 PP, CI -1.5,-0.1). There was no association between the IW Agreement and risk of SA in the mental health diagnosis group (overall: 0.0 PP, CI -0.3,0.3). Significant associations were found in the electricity (males: 5.2 PP, CI 0.4,10.0) and wholesale/retail sectors (females: -4.9 PP, CI -8.9,-1.0) for musculoskeletal diagnoses, and in the financial/real estate sector (overall: 1.6 PP, CI 0.2,2.9, females: 3.1 PP, CI 0.2,5.9) for mental health diagnoses.

Conclusions Women in companies with an IW Agreement had a significant reduction in one year risk of SA for musculoskeletal diagnoses. Gender and industry may modify the association between the IW Agreement and SA in musculoskeletal and mental health diagnoses.