Klinefelter syndrome (KS) is a sex chromosome disorder affecting 1:660 males (Stochholm et al., 2012). KS affects physical, cognitive, and psychological functioning. Physically, the main concerns are related to hypogonadism, reduced testosterone levels, and accompanying infertility. Cognitively, the average intellectual level of men with KS is normal, albeit lower than among non-KS controls, and with higher performance IQ relative to verbal IQ (Skakkebæk et al., 2014, 2015). Impaired executive functioning, as well as poor expressive and impressive language skills have been documented (Fjermestad et al., 2020; Gravholt et al., 2018; Leggett et al., 2010). Psychologically, men with KS report more psychological distress, as well as lower wellbeing and life satisfaction relative to controls (de Ronde et al., 2009; Herlihy et al., 2011; Skakkebæk et al., 2014). There is a higher risk for poor emotion regulation skills, as well as depression, anxiety, attention deficit hyperactivity disorder, and schizophrenia (Skakkebæk et al., 2015; van Rijn, et al., 2006).
Despite the documentation of several risk factors, there are still knowledge gaps regarding KS. Sleep is an important domain with emerging, yet limited, evidence of problems for men with KS. Sleep disturbance is associated with several negative factors such as poor socio-economic status, mental health problems, and neuropsychological difficulties, all of which are prevalent in men with KS (Altman et al., 2012). Given the vast amount of documentation of a reciprocal relationship between sleep and various health domains (e.g., Grandner, 2017; Hudson et al., 2020), it seems evident that there may be particular issues with sleep also for men with KS, due to their many health challenges. However, surprisingly little research has addressed sleep for this group. We know of two studies that have examined sleep in men with KS. The first was a self-report survey with 53 adults which found that men with KS reported poorer subjective sleep quality, more sleep disturbances, more tiredness affecting daytime functioning, and more use of sleep medication compared to Norwegian normative data (Fjermestad & Stokke, 2018). These data were collected using the self-reported Pittsburgh Sleep Quality Index (PSQI; Buysse et al., 1989). A later study used an objective sleep measure, i.e., actigraphy watches, to measure sleep over seven consecutive nights in 30 men with KS and age-matched controls (Fjermestad et al., 2020). Eight sleep domains were measured. The only domain that significantly differed between the groups was duration of night wakes, measured as the combined duration of the wakes after sleep onset. There were no differences between men with KS and controls in the other domains, which were time going to bed and getting out of bed, number of hours spent in bed, number of minutes awake in bed before falling asleep, sleep duration, number of times waking up during the night, or sleep efficiency, i.e., the percentage of time spent sleeping in bed.
Considered together, these studies suggest that there may be discrepancies between subjective and objective sleep measures for men with KS. This is in line with studies from the general population, in which there is a tendency towards little agreement between objective and subjective measured sleep (Girschik et al., 2012; Mezick et al., 2014). Nevertheless, there are reasons why further examination of the potential objective-subjective sleep inconsistency for men with KS is warranted. Subjective reports may be particularly difficult for men with KS due to their language problems. Furthermore, because many health issues in KS may be further impacted by disturbed sleep, sleep may be of key importance for clinicans and patients. Disentangling the role of sleep relative to other problem areas for men with KS may represent a clinical challenge, and it is therefore important to identify the most efficient ways of measuring sleep for this group.
In the current study, we build on the actigraphy data collected from men with KS in a previous study (Fjermestad et al., 2020) and examine these in relation to subjective sleep measures. We proposed three research questions. First, are there significant differences in objective (actigraphy) and subjective (questionnaire, sleep diary) measures of sleep within the KS sample? Since such discrepancies are common in the general population (e.g., Mezick et al., 2014), we also expected significant differences in the KS sample. Second, are there differences in objective (actigraphy) and subjective (questionnaire, sleep diary) measures of sleep for men with KS compared to non-KS controls? Due to the many psychosocial health difficulties reported in KS, we expected more sleep problems for men with KS than for controls. Third, are the socio-demographic variables age, educational level, vocational status, IQ, and mental health associated with sleep variables, above and beyond KS status? We examined this because the physical, social, cognitive, and psychological difficulties typically affecting men with KS may be associated with both objectively and subjectively measured sleep. Due to the paucity of research on sleep in KS, we explored this research question without a priori hypotheses.