Aging and Positive Mood: Longitudinal Neurobiological and Cognitive Correlates.

ABSTRACT

OBJECTIVE: Despite the losses commonly associated with aging, older adults seem to possess particularly preserved emotional regulation. To further understand this phenomenon, the authors examined longitudinal trajectories between age, depressive symptoms, brain structure, and cognition. METHODS: Seven hundred and sixteen functionally intact older adults (age M = 67.9, 56.8% female), followed longitudinally (visit range 1-13, M = 2.5), completed cognitive testing and the Geriatric Depression Scale (GDS). A subset (N = 327) underwent 3T brain MRI. Mixed-effects linear regression models were conducted controlling for sex, education, and total intracranial volume. RESULTS: There was a significant interaction between age and time on GDS, such that GDS improved with increasing age over time, but attenuated around age 71 (age*time b = 0.10, p <0.001). Fractional anisotropy (FA) and mean diffusivity interacted with age to predict longitudinal changes in GDS (FA b = -0.02, p = 0.01; MD b = 0.03, p = 0.007), such that age-related benefits on GDS were attenuated in those with declining FA. Executive function (EF) and processing speed also interacted with age to predict longitudinal changes in GDS (EF b = -0.04, p = 0.03; speed b = 0.04, p = 0.04). Again, the positive effect of age on GDS attenuated in those with worsening EF and speed. There were no associations with memory, semantic fluency, or gray matter (p values >0.05). CONCLUSION: EF, processing speed, and white matter integrity moderated the longitudinal relationship between age and mood. Previous studies demonstrate the link between positivity and better cognitive control, leading to improved mood in older adults. Our results are not only consistent, but establish a potential neurobiological correlate. Future research further exploring biological mechanisms driving psychological processes may have important therapeutic implications.