Abstract
The aim of this study was to investigate whether the nighttime cortisol release was associated with subjective and objective sleep quality and the discrepancy between them. Forty-five healthy older adults (age range from 56 to 75 years) collected salivary samples immediately before sleep and immediately after awakening on two consecutive nights. Actigraphy was used to assess objective sleep quality and quantity. A sleep diary was used to assess subjective sleep quality. Linear mixed models were performed using subjective and objective sleep quality data from 76 nights to investigate between-subject associations. We observed that larger changes in cortisol levels between sleep onset and awakening, reflecting a healthier circadian rhythm of the Hypothalamic-Pituitary-Adrenal (HPA) axis, were associated with better subjective sleep quality, but not with objective sleep quality. Moreover, smaller changes in nighttime cortisol were associated with lower subjective sleep quality relative to objective sleep quality. All these results were observed even after controlling for important confounders such as sleep quantity, age, sex, subjective socioeconomic status, stress perception, depression, physical activity, and adherence to the salivary sampling protocol. This study demonstrates that subjective sleep quality in older people may be explained, to some extent, by the activity of the HPA axis.
Highlights
Normative aging is associated with changes in sleep patterns [1]
This study demonstrates that subjective sleep quality in older people may be explained, to some extent, by the activity of the Keywords: sleep quality; subjective sleep; objective sleep; older people; HPA axis; cortisol
As observed with the complete sample, these results showed that higher Cortisolchange was related to better subjective sleep quality (Controlling for sleep quantity: (F(1,64) = 16.234, p < 0.001, 95% CI
Summary
Normative aging is associated with changes in sleep patterns [1]. Previous research has identified reduced sleep quality as one of the most critical changes in healthy aging. Reduced sleep quality has been associated with important age-related health problems, such as cognitive deficits, including higher risk of dementia, mood disorders, and cardiovascular disease [2,3,4]. Investigating the factors associated with sleep quality may offer critical evidence to understand, prevent, and treat sleep problems and the negative effects of sleep problems in older people. An association between subjective and objective measures of sleep quality is expected, several studies in older people have demonstrated discrepancies between these two measures [7,8]. Public Health 2020, 17, 1264; doi:10.3390/ijerph17041264 www.mdpi.com/journal/ijerph
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