Men who reported sleep problems, including difficulty falling asleep and staying asleep, had up to a twofold increased risk for prostate cancer, according to data published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.
“Sleep problems are very common in modern society and can have adverse health consequences,” said Lara G. Sigurdardóttir, M.D., at the University of Iceland in Reykjavik. “Women with sleep disruption have consistently been reported to be at an increased risk for breast cancer, but less is known about the potential role of sleep problems in prostate cancer.”
Previous studies have generated conflicting results for an association between sleep disruption from working night shifts and the risk for prostate cancer. Sigurdardóttir and her colleagues, therefore, investigated the role of sleep in influencing prostate cancer risk.
The researchers followed 2,102 men from the prospective Age, Gene/Environment Susceptibility-Reykjavik study, which involved an established, population-based cohort of 2,425 men aged 67 to 96. Upon enrollment into the study, the participants answered four questions about sleep disruption: whether they took medications to sleep, had trouble falling asleep, woke up during nights with difficulty going back to sleep or woke up early in the morning with difficulty going back to sleep.
Among the participants, 8.7 percent and 5.7 percent reported severe and very severe sleep problems, respectively. None of the participants had prostate cancer at study entry. The researchers followed the participants for five years, and during this period, 6.4 percent were diagnosed with prostate cancer.
After the researchers adjusted for age, they found that compared with men who reported no problems with sleeping, the risk for prostate cancer increased proportionately with reported severity of problems falling and staying asleep, from 1.6-fold to 2.1-fold. Further, the association was stronger for advanced prostate cancer than for overall prostate cancer, with more than a threefold increase in risk for advanced prostate cancer associated with “very severe” sleep problems.
Circadian disruption, sleep loss, and prostate cancer risk: a systematic review of epidemiologic studies
Disruption of the circadian system has been hypothesized to increase cancer risk, either because of direct disruption of the molecular machinery generating circadian rhythms or because of disruption of parameters controlled by the clock such as melatonin levels or sleep duration. This hypothesis has been studied in hormone-dependent cancers among women, but data are sparse about potential effects of circadian disruption on the risk of prostate cancer. This review systematically examines available data evaluating the effects of light at night, sleep patterns, and night shift work on prostate cancer risk.
Sigurdardottir LG, Valdimarsdottir UA, Fall K, Rider JR, Lockley SW, Schernhammer E, Mucci LA.
To rule out the possibility that the problems with sleeping were because of undiagnosed prostate cancer or an enlarged prostate, the researchers reanalyzed the data after excluding men with symptoms of sleep disturbance that might be indicative of nocturia (waking up during the night to urinate). The results remained unchanged.
According to Sigurdardóttir, these data should be confirmed with a larger cohort with longer observation times. “Prostate cancer is one of the leading public health concerns for men and sleep problems are quite common,” she said. “If our results are confirmed with further studies, sleep may become a potential target for intervention to reduce the risk for prostate cancer.”
Sleep duration and the risk of prostate cancer: the Ohsaki Cohort Study
Sleep duration is associated with various health outcomes (Youngstedt and Kripke, 2004) including three observational studies of sleep duration and breast cancer (Verkasalo et al, 2005; McElroy et al, 2006; Pinheiro et al, 2006). Melatonin, which is secreted mainly from the pineal gland and plays a role in sleep duration, is suggested as one of the candidates responsible for the association in breast cancer (Brzezinski, 1997; Schernhammer and Schulmeister, 2004) as it influences the synthesis and secretion of sex hormones by promoting the release of gonadotropin-releasing hormone (Martin and Klein, 1976; Aleandri et al, 1996).
In relation to melatonin, there have been several observational studies of night work, shift work or visual impairment, and sex hormone-related cancers such as prostate or breast (Feychting et al, 1998; Verkasalo et al, 1999; Kliukiene et al, 2001; Megdal et al, 2005; Kubo et al, 2006; Conlon et al, 2007; Schwartzbaum et al, 2007). However, there has been no study of sleep duration and prostate cancer risk, even though prostate cancer, like breast cancer, is also a sex hormone-related cancer.
We therefore examined the association between sleep duration and prostate cancer risk in a population of Japanese men, in whom the mortality of prostate cancer is increasing (Statistics and Information Department, Minister’s Secretariat, Ministry of Health Labour and Welfare of Japan, 2007).
M Kakizaki, K Inoue, S Kuriyama, T Sone, K Matsuda-Ohmori, N Nakaya, S Fukudo and I Tsuji
Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
Division of Behavioral Medicine, Department of Functional Medical Science, Tohoku University Graduate School of Medicine, Sendai, Jap
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