Subjective insomnia symptoms and sleep duration are not related to hypothalamic–pituitary–adrenal axis activity in older adults RIAN J. G. PETERS VAN NEIJENHOF 1 , ERIK VAN DUIJN 1,2 , JULIA F. VAN DEN BERG 3,4 , MARGOT W. M. DE WAAL 5 , ROOS C. VAN DER MAST 2,6 and HANNIE C. COMIJS 7 1 Center for Mental Health Care Delfland, Delft, The Netherlands; 2 Department of Psychiatry, Leiden University Medical Center, Leiden, The Netherlands; 3 Parnassia Psychiatric Institute, Den Haag, The Netherlands; 4 Department of Clinical Psychology, Leiden University, Leiden, The Netherlands; 5 Department of Public Health and Primary Care, Leiden University Medical Center, Leiden, The Netherlands; 6 Department of Psychiatry, CAPRI-University of Antwerp, Antwerp, Belgium; 7 Department of Psychiatry/EMGO Institute for Health and Care Research, VU University Medical Center, GGZ InGeest, Amsterdam, The Netherlands Keywords sleep disturbances, HPA-axis, cortisol levels, old age, depressive mood Correspondence Rian Peters van Neijenhof, Centre for Mental Health Care Delfland, Sint Jorisweg 2, 2612GA Delft, The Netherlands. Tel.: +31-15-2607607; fax: +31-15-2120272; e-mail: r.petersvanneijenhof@ggz-delfland.nl Accepted in revised form 26 April 2017; received 14 December 2016 DOI: 10.1111/jsr.12570 SUMMARY Insomnia symptoms are highly prevalent in depressed older adults. This study investigates the association between hypothalamic–pituitary– adrenal (HPA) axis activity and symptoms of insomnia, respectively, sleep duration among 294 depressed and 123 non-depressed older adults of the Netherlands Study of Depression in Older people (NESDO) study. Insomnia symptoms were defined as clinically relevant when having a score ≥ 10 points on the Women’s Health Initiative Insomnia Rating Scale (WHIIRS). Sleep duration was categorized in short (≤ 6h per night), normal (7–8 h per night) and long (≥ 9 h per night) duration. Salivary cortisol levels were used to assess the following cortisol parameters for HPA axis activity: area under the curve with respect to the increase (AUCi) and to the ground (AUCg), diurnal slope, evening cortisol level and dexamethasone suppression ratio. Clinically relevant insomnia symptoms were present in 46% of the participants. Thirty-two per cent of the participants were short sleepers, whereas 16% were long sleepers. However, univariate analyses showed no differences in any of the HPA axis parameters between people with and without insomnia symptoms or between the three groups with different sleep duration. In addition, no significant interaction was found between a diagnosis of depression or the severity of depressive symptoms and any of the cortisol parameters in relation to insomnia symptoms or sleep duration. INTRODUCTION Symptoms of insomnia are common in late life, with preva- lences in non-institutionalized older adults ranging from 20 to almost 50% (Ohayon, 2002; Ohayon and Reynolds, 2009). Disturbances in sleep have a major impact on quality of life and increase the risk of falls (Stone et al., 2014), substance use and physical and mental health problems, such as depression (Foley et al., 2004). It has been suggested that sleep disturbances might be associated with dysregulation of the hypothalamic–pituitary–adrenal (HPA) axis (Buckley and Schatzberg, 2005). A cascade of processes in the HPA axis results in the excretion of cortisol in a diurnal rhythm, with a post-awakening increase (Elder et al., 2014; Pruessner et al., 1997) followed by a decline throughout the day, reaching the lowest point during the first half of the nightly sleep period and rising again until the morning (Weitzman et al., 1971). To measure the negative feedback loop of the HPA axis, the dexamethasone suppression test (DST) was developed (APA, 1987) initially to diagnose Cushing’s disease. The DST has also been proposed as a biomarker of psychiatric diseases such as depression (American Psychiatric Association, 1987). Dexamethasone suppresses the nocturnal production of adrenocorticotrophic hormone (ACTH), resulting in low cortisol levels the next morning (Buckley and Schatzberg, 2005). However, research ª 2017 European Sleep Research Society 40 J Sleep Res. (2018) 27, 40–46 Sleep hygiene, insomnia and mental health