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Less sleep may increase risk for death in younger men with prostate cancer
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Younger men with prostate cancer had a significantly higher risk for death of the disease if they slept less than 7 hours per night, according to data presented at the American Association for Cancer Research Annual Meeting.
“There is growing interest in determining the potential health effects of factors that disrupt circadian rhythms, such as shift work and lack of sleep,” Susan M. Gapstur, PhD, MPH, vice president of epidemiology at the American Cancer Society, said in a press release.
Previous research suggested associations between shorter sleep durations and prostate cancer morbidity. Gapstur and colleagues analyzed data from the Cancer Prevention Study-I (CPS-I), which followed 407,649 men from 1950 through 1972, and CPS-II, which followed 416,040 men from 1982 through 2012. Study participants — who were cancer free at baseline — reported sleep-related behaviors, such as sleep duration, shift work and insomnia.
During follow-up, 1,546 men from CPS-I and 8,704 men from CPS-II died of prostate cancer.
In the first 8 years of follow-up, men aged younger than 65 years who reported they slept 3 to 5 hours per night had a greater risk for dying of prostate cancer (RR = 1.61; 95% CI, 1.1-2.37) than men who slept 7 hours per night. Men who slept 6 hours per night exhibited a greater risk (RR = 1.25; 95% CI, 0.99-1.58).
Interestingly, men aged 65 years and older showed no association between sleep duration and risk for death of prostate cancer whether they slept 3 to 5 hours (RR = 0.97; 95%, 0.68-1.38) or for 6 hours (RR = 1.02; 95% CI, 0.82-1.27).
Gapstur noted that sleep deprivation and the presence of light at night while working an overnight shift can inhibit the natural production of melatonin, a hormone that affects sleep cycles. Low melatonin production can spark increased genetic mutations, greater oxidative damage, reduced DNA repair and immune suppression. Additionally, short sleep durations of 3 to 5 hours may also contribute to the dysregulation of genes involved in tumor suppression.
It is unclear why data suggest no association between sleep duration and prostate cancer death in older men, although it might be related to the natural decline in nocturnal melatonin levels with age, Gapstur said.
“While these results are intriguing and contribute to a growing body of evidence that circadian rhythm–related factors might play a role in prostate carcinogenesis, more research is needed to better understand the biologic mechanisms,” Gapstur said. “If confirmed in other studies, these findings would contribute to evidence suggesting the importance of obtaining adequate sleep for better health.” – by Chuck Gormley
Reference:
Gapstur SM, et al. Abstract 2306. Presented at: AACR Annual Meeting; April 1-5, 2017; Washington, D.C.
Disclosure: The American Cancer Society funded this study. Gapstur reports no relevant financial disclosures.
Perspective
Back to TopThomas A. Sellers, PhD, MPH; and Heather S. Jim, PhD
At the 2017 American Association for Cancer Research Annual Meeting, Susan M. Gapstur, PhD, MPH, vice president of epidemiology at the American Cancer Society, presented results from two ongoing cohort studies of over 825,000 men. Participants provided responses to questions about sleep-related behaviors — such as sleep duration, shift work and insomnia — and were followed for subsequent death of prostate cancer.
Duration of follow-up was up to 30 years, and more than 10,000 deaths from prostate cancer were documented. Results showed that, compared with men who reported 7 hours per night of sleep, those who reported only 6 hours had a 29% increased risk for death of prostate cancer, and those who reported between 3 and 5 hours per night had a 55% greater risk. Interestingly, the association was only evident among men aged younger than age 65 years, and only for the first 8 years of follow-up. There were no differences in prostate cancer mortality by sleep duration patterns among older men, or for follow-up longer than 8 years.
This study contributes to robust scientific literature on sleep disturbance and health; the first publication appeared in 1964 and studies have been conducted around the world and subjected to meta-analysis. What is consistent across studies is that the association of sleep duration and health is U-shaped. People who sleep 7 to 8 hours per night have the lowest mortality; those who sleep too little or too much fare worse. Short sleep is associated with cancer, cardiovascular disease, cardiovascular events, diabetes and hypertension.
The ACS study confirms an earlier report and is notable for the large sample size and long duration of follow-up. The results could shed light on underlying mechanisms, which the researchers noted could be via reduction of melatonin levels or dysregulation of circadian rhythm genes that influence tumor suppression. The results may not only reflect biology, but also socioeconomic factors or other variables not included in the analysis.
Before rushing to sleep aids or melatonin tablets, it is important to note that the questions on sleep patterns were only asked once, and may have changed over time, especially given the long duration of the study. The study was only able to measure mortality, not incidence of the disease, and differences in clinical presentation and treatment should be considered, too. It remains unknown whether the relationship between sleep and prostate cancer mortality is causal. Nevertheless, randomized trials to improve sleep in cancer patients (eg, cognitive-behavioral therapy for insomnia) have demonstrated a variety of benefits, including better mood and quality of life.
The ACS study underscores the importance of good sleep in patients with prostate cancer and highlights the need for additional research to determine whether sleep interventions can improve disease outcomes.
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