Chapter 4 104 Abstract Women report poorer sleep than men, and oral contraceptive (OC) users appear to experience more disrupted sleep and poorer sleep quality relative to non-users, which potentially relate to disruption of circadian rhythms such as cortisol dynamics. This preregistered study evaluated sleep quality, sleep disruptions and the role of cortisol dynamics in naturally cycling (NC) women, OC users and men. In 242 healthy participants from the Cimbi database, we first compared selfreported sleep quality and sleep disruptions between the groups with probabilistic index and linear regression models, respectively. Second, we examined the role of the cortisol awakening response (CAR) in sleep by use of mediation or moderation analyses dependent on findings of group differences in the sleep outcomes. We show no significant differences in sleep disruptions in OC users (n=31), or in men (n=124) compared to NC women (n=87). OC users reported modestly poorer overall sleep quality compared to NC women (padjusted=0.042), but this difference was not mediated by the CAR. A lower CAR was associated with more sleep disruptions in OC users (-0.138 [-0.238; -0.039], p=0.006) and with poorer sleep quality in men (0.24 [-0.40; -0.08], p=0.003), but no associations with sleep were seen in NC women. In conclusion, we find modestly poorer sleep in healthy OC users compared to NC women, but no sex differences per se. Further, our data suggest a coupling between cortisol dynamics and sleep in OC users and men. Prospective studies are necessary to further assess the role of sex and OC use in cortisol dynamics and sleep.
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