Sleep problems have been shown to have broad deleterious effects. Difficulty sleeping was found to be predictive of psychiatric disorders (Ohayon & Roth 2003
; Taylor et al. 2003
) and was associated with medical conditions, such as heart disease and hypertension (Taylor et al. 2007
). Other consequences of difficulty sleeping include decreased cognitive functioning, daily accomplishments, enjoyment of relationships, emotional well-being, and quality of life (Chevalier et al. 1999
; Léger et al. 2008
; Roth & Ancoli-Israel 1999
; Vandekerckhove & Cluydts 2010
). Similarly, among patients with chronic illness, difficulty sleeping was associated with worse health-related quality of life after accounting for the effects of depression, anxiety, and medical comorbidities (Katz & McHorney, 2002
Previous survey studies suggest that prostate cancer patients on androgen deprivation therapy are vulnerable to sleep problems. Using more time-sensitive instruments, this study similarly found evidence of sleep problems in this population. Specifically, patients had trouble sleeping at the beginning and during the night, and daytime naps were common. Even though hot flashes are common in this population (Hanisch et al. 2009
), nocturia was reported by participants as the primary cause of awakenings. Most striking, the average sleep duration noted by both objective and subjective measures was approximately 6 hours per night.
In spite of low total sleep time, normal functioning was indicated by findings of circadian rhythmicity in activity levels and patient-reported general quality of life. Current reports of general quality of life appear consistent with previous androgen deprivation therapy studies (Arai et al. 2008
; Joly et al. 2006
; Sakai et al.
2009). Conversely, clinically significant daytime sleepiness was reported by 23% of participants, and actigraphy results suggest that participants were napping during the day. To our knowledge, sleepiness has not been assessed previously among prostate cancer patients on androgen deprivation therapy, but similar mean scores were found prior to and after radiotherapy for prostate cancer (Monga et al. 2005
Only patient-reported daytime sleepiness was related to objective total sleep time. This was contrary to our hypothesis that poor sleep would be related to multiple negative outcomes and suggests that daytime nap time and quality of life are not related to night-time sleep time. Likewise, another study found that older age was associated with fewer daytime symptoms despite increases in night-time sleep problems (Unruh et al. 2008
). It is possible that older adults adapt to age-related (Unruh et al. 2008
; Vitiello et al. 2004
; Zilli et al. 2009
) as well as treatment-related changes in sleep.
Low to moderate relationships were found between objectively measured and patient reports of sleep. Actigraphy detected worse sleeping patterns, consistent with other studies showing older men report better sleep on diaries compared to actigraphy (van den Berg et al. 2009
). This is expected as persons are not likely to recall accurately when in a state of reduced consciousness, resulting in reporting biases, such as an overestimation of night-time sleep. On the other hand, although actigrapy is a validated measure of sleep, it is not accurate at differentiating between sleep versus restful wake periods, and wake versus periodic limb movements during sleep (Tryon 2004
). These different sources of error may account for the weak relationships between actigraphy and diary-based estimates and support use of both measures for a comprehensive assessment of sleep.
This study had limitations. Data was obtained from a convenience sample, so results may not generalize. Future studies including a more representative sample may find that poor sleep has broader negative effects. Similar results may have been found if a control group of men not on androgen deprivation therapy or diagnosed with prostate cancer was included. However, such findings would not alter the implications for therapeutic targets or effects on daily life. Another primary limitation of the current study was the use of retrospective patient report for identifying the causes of awakenings at night. Participants may have recalled awakening mostly due to nocturia and hot flashes because both are salient events.
In conclusion, this study provides further evidence of poor sleep among prostate cancer patients on androgen deprivation therapy. It specifically showed that patients had problems with sleeping at the beginning and throughout the night and highlights the need to provide distressed patients with effective interventions targeting sleep latency and disruption. Results suggests that nocturia and hot flashes are common causes of sleep disruption in this population, but there may be other contributing factors, such as sleep apnoea and emotional distress, that are not as readily detected or associated with sleep problems by patients. More research is needed to identify the effect of each factor on sleep in order to provide more tailored interventions for patients.