Affect, worry, and sleep: Between- and within-subject associations in a diary study

Objectives: Little is known about the daily associations between affect, worry, and sleep problems, and previous studies did not distinguish differences between persons from differences within persons. We examined bidirectional associations of daily unpleasant affect (UA), pleasant affect (PA), and worry with sleep problems at both the between- and the within-persons level.

Methods: The data came from a web-based diary study called “HowNutsAreTheDutch”, in which 1,165 respondents filled out an online questionnaire 3 times a day, for 30 consecutive days. Daily levels of affect and worry were calculated by averaging the morning, afternoon, and evening scores. Sleep problems were assessed in the morning, with regard to the previous night. Bidirectional associations between affect, worry, and sleep problems were tested using Dynamic Structural Equation Modeling (DSEM).

Results: High UA, low PA, high worry, and poor sleep were strongly associated at the between-person level. At the within-person level, better-than-usual sleep at night significantly predicted lower UA (β = -0.31, p <.001) and worry (β = -0.16, p <.001) and higher PA (β = 0.29, p <.001) during the subsequent day. The effects from daytime affect and worry to sleep the subsequent night were also significant, but considerably weaker.

Limitations: Women and highly educated individuals were overrepresented in our sample.

Conclusions: Persons who sleep worse than usual at night are likely to experience less PA and more UA and worry the following day. Daytime UA, PA, and worry also predict sleep problems during the following night, but to a lesser extent than the reverse effects.