AimsStudying birth-cohort differences in depression incidence and their explanatory factors may provide insight into the aetiology of depression and could help to optimise prevention strategies to reduce the worldwide burden of depression.MethodsData were used from the Longitudinal Aging Study Amsterdam, a nationally representative study among community dwelling older adults in the Netherlands. Cohort differences in depression incidence over a 10-year-period (score ≥16 on the Center for Epidemiologic Studies Depression scale) were tested using a cohort-sequential-longitudinal-design, comparing two identically measured cohorts of non-depressed 55-64-year-olds, born 10-years apart. Baseline measurements took place in 1992/93 (early cohort, n = 794), and 2002/03 (recent cohort, n = 771). As indicated by the dynamic equilibrium model of depression, potential explanatory factors were distinguished in risk and protective factors.ResultsThe incidence rates for depression in the early and recent cohort were 1.91 (95% confidence interval (CI) 1.59-2.27) and 1.60 (95% CI 1.31-1.94) per 100 person-years, respectively. A 29% risk reduction in depression incidence was observed in the recent cohort (HRcohort: 0.71, 95% CI 0.54-0.92, p = 0.011), as compared with the early cohort, even though average levels of risk factors such as chronic disease and functional limitations had increased. This reduction was primarily explained by increased levels of education, mastery and labour market participation.ConclusionsThese findings suggest that favourable developments of protective factors have counterbalanced unfavourable effects of risk factors on the incidence of depression, resulting in a net reduction of depression incidence among young-old adults. However, maintaining a good physical health must be a priority to further decrease depression rates.