Introduction There has been increasing attention on work ability promotion and prolonging working life in Norway. The aim of this study was to investigate the association between several lifestyle-related risk factors (unhealthy diet, low physical activity, overweight/obesity and smoking) and self-rated work ability.

Methods This study is based on the Telemark study, a cross-sectional population study conducted in Telemark county, Norway in 2013. Complete data on lifestyle-related factors and work ability were obtained for 10 434 participants aged 18–50 years, all engaged in paid work during the past 12 months. The outcome measure was the first single item question of the work ability index (WAI). We used multiple logistic regression analysis to examine the associations with the independent variables: diet, body mass index, physical activity and smoking. We adjusted for age, gender, education and main occupational group and stratified for age groups (18–30, 31–40 and 41–50).

Results Reduced work ability (score <8) was more likely among obese participants (OR 1.5, 95% CI: 1.3 to 1.7), past and current smokers (OR 1.3, 95% CI: 1.1 to 1.5 and OR 1.4, 95% CI: 1.2 to 1.6 respectively), inactive individuals (OR 1.4, 95% CI: 1.3 to 1.6), and persons responding to have an unhealthy diet (OR 1.3, 95% CI: 1.0 to 1.5). Among participants aged 18–30 years, inactivity and smoking were associated with deceased work ability, while among participants aged 41–50 years, all the studied lifestyle-related factors were significantly associated with decreased work ability.

Discussion Lifestyle-related risk factors were found to be associated with reduced work ability in a general working population aged 18–50. The results indicate that workers may benefit from interventions focusing on multiple life style changes. The findings further indicate an increased importance of lifestyle-related behaviours on work ability with age. The results are considered relevant to occupational intervention health programs aimed at prevention of decreased work ability.