Optimism and Sleep in Aging Women: Bidirectional Relationships.

Objective: Sleep quality and duration are important for biological restoration and promotion of psychological well-being. Optimism may facilitate or result from sufficient sleep, but questions remain as to directionality. The present study tested how optimism is associated with levels of and variability in sleep quantity and quality in a longitudinal burst design.

Methods: Midlife and older women ( N = 199) reported their sleep quantity and quality in online diaries for a 7-day period, every 3 months for 2 years. Optimism was measured at baseline and end-of-study. Multilevel models tested the effects of optimism on sleep. Linear regression models tested the effect of sleep on optimism.

Results: Baseline optimism was associated with higher sleep quality ( γ = 2.13 [1.16 to 3.11], p < .0001) and lower intraindividual variability (IIV; night-to-night and wave-to-wave) in sleep quantity (night-to-night: γ = -0.07 [-0.13 to -0.005], p = .03; wave-to-wave: b = -0.07 [-0.12 to -0.02], p = .003). In turn, higher average sleep quality (but not quantity) was associated with higher optimism at end-of-study ( b = 0.02 [0.007 to 0.03], p = .002). Variability in sleep was unrelated to optimism.

Conclusions: Optimism may play an important role in maintaining sleep quality and consistency in sleep quantity, perhaps by buffering stress. Similarly, sleep quality may play an important role in maintaining optimism. The cycle whereby optimism and sleep enhance one another could improve physical health and psychological well-being among aging adults.