Chronic health conditions, multimorbidity and subsequent economic inactivity in three British birth cohorts

Background. Economic inactivity due to ill-health has been rising in the United Kingdom. Chronic health conditions make up most of the burden of poor health, and frequently co-occur, yet the impact of multimorbidity on economic inactivity remains underexplored. Methods. Data was from three British birth cohorts (born in 1946, 1958 and 1970). Psychological distress, chronic back pain and cardiometabolic disease were assessed in participants' thirties and forties, and economic inactivity one to two decades later. Modified Poisson regression models with robust standard errors estimated associations between health and inactivity, accounting for economic activity at baseline and several socioeconomic and demographic confounders. We tested for multiplicative and additive interaction between condition pairs. Results. The prevalence of all three health conditions increased with age. Each was associated with a higher risk of later economic inactivity in fully adjusted models. Psychological distress was the strongest and most consistent predictor across cohorts (RR = 1.22 (95% CI 0.90-1.64) to 1.99 (95% CI 1.67-2.38)). Comorbidity was common; more than 10% of participants experienced two or more conditions in their forties. Risk of economic inactivity increased with multimorbidity. However, we found little evidence that risk for comorbidity exceeded the sum of individual conditions on either the multiplicative or additive scales. Conclusions. Common chronic conditions in adulthood, particularly when comorbid, are associated with a substantially higher risk of economic inactivity across decades-long time horizons. This association has persisted over time and across policy contexts.