Dyadic associations between sleep quality, diet-related self-regulation, and diet quality in couples

Although poor sleep is known to impair diet quality and self-regulation, research has primarily examined these effects within individuals. For cohabiting couples, one partner's poor sleep may affect both partners' diet quality.

This study examined whether sleep quality is associated with both one's own and one's partner's diet quality, and whether impaired self-regulation processes linked partners' poor sleep and poor diet quality.

We conducted a 3-month dyadic longitudinal study with 204 cohabiting couples (N = 408; M age = 42.4 years). Participants completed assessments of sleep quality (Pittsburgh Sleep Quality Index) and diet quality (Starting the Conversation on Diet) at baseline, 1-month, and 3-month follow-ups. Following baseline, participants completed a 14-day daily diary assessing diet-related self-regulation based on the Health Action Process Approach.

Using Actor-Partner Interdependence Models, we found both actor (b = 0.07; 95% CI, 0.01-0.13; P = .026) and partner effects (b = 0.10; 95% CI, 0.04-0.16; P = .001) of sleep quality on diet quality at baseline, indicating that an individual's sleep quality was independently associated with both their own and their partner's diet quality. Similarly, there were actor and partner effects of sleep quality on self-regulatory effort and self-efficacy. There were significant indirect effects of partners' sleep quality on the actor's diet quality through the actor's self-regulatory effort and self-efficacy.

Poor sleep quality has both individual and dyadic associations with diet quality in couples. Poor sleep in one partner is also associated with impaired diet-related self-regulation in both partners.