Secular trends in the prevalence of major and subthreshold depression among 55-64-year olds over 20 years.

BACKGROUND: Studying secular trends in the exposure to risk and protective factors of depression and whether these trends are associated with secular trends in the prevalence of depression is important to estimate future healthcare demands and to identify targets for prevention.

METHODS: Three birth cohorts of 55-64-year olds from the population-based Longitudinal Aging Study Amsterdam were examined using identical methods in 1992 (n = 944), 2002 (n = 964) and 2012 (n = 957). A two-stage screening design was used to identify subthreshold depression (SUBD) and major depressive disorder (MDD). Multinomial logistic regression analyses were used to identify secular trends in depression prevalence and to identify factors from the biopsychosocial domains of functioning that were associated with these trends.

RESULTS: Compared with 1992, MDD became more prevalent in 2002 (OR 1.90, 95% CI 1.10-3.28, p = 0.022) and 2012 (OR 1.80, 95% CI 1.03-3.14, p = 0.039). This was largely attributable to an increase in the prevalence of chronic diseases and functional limitations. Socioeconomic and psychosocial improvements, including an increase in labor market participation, social support and mastery, hampered MDD rates to rise more and were also associated with a 32% decline of SUBD-rates in 2012 as compared with 2002 (OR 0.68, 95% CI 0.48-0.96, p = 0.03).

CONCLUSIONS: Among late middle-aged adults, there is a substantial net increase of MDD, which is associated with deteriorating physical health. If morbidity and disability continue to increase, a further expansion of MDD rates may be expected. Improving socioeconomic and psychosocial conditions may benefit public health, as these factors were protective against a higher prevalence of both MDD and SUBD.