The co-occurrence of diabetes mellitus and depression, especially in persons younger than 65 years, poses an important hazard to healthy brain aging and cognitive fitness in the later years of life. Katon and colleagues1 from Denmark contribute this key observation in this issue of JAMA Psychiatry.
This observation raises questions about the biology of aging and about promotion of ways of aging well, not just living a long life. First, with respect to the basic biology of aging, how does aging enable disease? Second, from the perspective of population health, how can we narrow the gap between life span and health span, compressing the period of functional morbidity (especially related to dementia) in the later years of life? The answers to the first question will likely provide important clues for answering the second.2