Sleep Alterations in Non-demented Older Individuals: The Role of Cortisol

Background: Sleep alterations can impair quality of life and contribute to disease progression but they, and their features and contributing factors, are rarely analysed in institutionalised older individuals. In this study, we investigated sleep alterations, the factors involved, and the role of cortisol in sleep-related problems in institutionalised individuals. Methods: We conducted a descriptive cross-sectional study in participants living in nursing homes in Valencia (Spain); sleep alterations were determined based on two validated tools: the Athens insomnia scale and Oviedo sleep questionnaire. Plasma cortisol was measured in the morning and determined by high performance liquid chromatography-mass spectroscopy, along with other blood analytical parameters. We also analysed any confounding factors (sleep duration, morning awakening time, intake of hypnotic and psychotropic medication, and cognitive function). Results: The mean age was 82.5 years (range: 65-99); approximately 80% were women and sleep alterations were present in 25-60% of the population, depending on the scale used or type of sleep disorder considered. There was no significant correlation between morning cortisol concentrations and sleep disorders, sex, age, or psychotropic drug ingestion (including hypnotic drugs). However, there was a significant correlation between cortisol and an Oviedo questionnaire subscale for evaluating insomniarelated adverse events, which remained significant after adjusting for multiple potentially confounding factors. Conclusion: Sleep disorders are common in institutionalised older individuals and are not related to sleep duration or decreased by ingestion of hypnotic medications. There is a significant relationship between morning cortisol levels in blood and insomnia-related sleep disorders (e.g. snoring with awakenings, nightmares, restless legs syndrome, etc.) but not directly with insomnia or hypersomnia.