Eveningness in Middle-Aged and Older Adults: Associations With Sleep, Internalising Symptoms, and Alertness.

Evening chronotype, characterised by a preference for later circadian timing, can present challenges in societal activities oriented towards morning schedules. This study investigates the link between chronotype and sleep, alertness, and internalising symptoms in middle-aged and older adults. The sample comprised 652 healthy adults (ages 35-98) free of sleep, psychiatric, or neurological disorders. All participants completed a 3-min version of the Psychomotor Vigilance Test both in the morning and evening, where the median reaction time served as a measure of behavioural alertness. Additionally, participants completed: (1) the Morningness-Eveningness Questionnaire for chronotype, (2) the Stanford Sleepiness Scale for subjective alertness, (3) the Pittsburgh Sleep Quality Index for sleep disturbance, and (4) the Mood and Anxiety Symptom Questionnaire for depression-specific anhedonia, anxiety-specific anxious arousal, and the common internalising factor, general distress. Results indicated that endorsing an evening chronotype provided a transdiagnostic risk factor for general distress, anhedonia, anxious arousal, as well as sleep disturbance and morning subjective sleepiness across middle-aged and older adults. Evening chronotypes showed higher behavioural alertness in the evening, compared to both intermediate and morning chronotypes. These results suggest that chronotype should be considered when promoting healthy ageing and optimal performance.