Lack of Sleep Linked to Increased Risk of Cancer

 By Leah Lawrence

Source: https://www.cancertherapyadvisor.com/

Getting less than 6 hours of sleep each night was associated with an increased risk of cancer. Source: Getty Images

Getting less sleep is associated with an increased risk of cancer, according to a study published in the journal Cancer.

Researchers found evidence to suggest that individuals who slept less than 6 hours each night, those who did not nap during the day, and those who got less than 7 hours of sleep in total had an increased risk of cancer.  

For this study, the researchers analyzed data from 14,851 participants in the China Health and Retirement Longitudinal Study, a population-based survey of people older than 45 years of age. The researchers evaluated associations between cancer and nighttime sleep duration, daytime napping, and total sleep duration.

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The study participants’ mean age was 58.78 years, 53% were women, 29% slept for less than 6 hours per night, and 46.9% did not take naps during the day. Over a median follow-up of 6.9 years, there were 229 cases of incident cancer.

In a multivariable analysis, individuals who slept less than 6 hours per night had a 41% higher risk of cancer than those who slept for 6-8 hours per night (hazard ratio [HR], 1.41; 95% CI. 1.01-1.95; P =.041). When the researchers stratified patients by sex, this association was only significant for women (HR, 1.53; 95% CI, 1.00-2.33; P =.047).

Individuals who did not nap during the day had a 60% higher risk of cancer than those who napped for more than 1 hour per day (HR, 1.60; 95% CI, 1.01-2.55; P =.047). There was no variation in risk by sex.

Individuals who slept less than 7 hours in total had a 69% higher risk of cancer than those who slept for 7-8 hours total (HR, 1.69; 95% CI, 1.19-2.39; P =.003). When the researchers stratified participants by sex and body mass index (BMI), there was a significantly increased cancer risk associated with less than 7 hours of total sleep for men (HR, 1.95; 95% CI, 1.14-3.35; P =.015) and for individuals with a BMI of 24 kg/m² or more (HR, 1.70; 95% CI, 1.06-2.75; P =.029). The difference for women and individuals with a BMI of less than 24 kg/m² did not reach statistical significance.

The researchers also analyzed sleep trajectories over time in 9788 participants. Compared to participants who had a normal sleep trajectory throughout follow-up, those who maintained a short sleep duration — at nighttime only or in total — did not have a significantly increased risk of cancer overall.

However, when participants were stratified by sex and BMI, the risk of cancer was increased among women (HR, 2.01; 95% CI, 1.07-3.80; P =.030) and those with a BMI of 24 kg/m² or higher (HR, 1.87; 95% CI, 1.01-3.45; P =.046) if they maintained a short trajectory of nighttime sleep duration. The risk of cancer was also increased among women who maintained a short trajectory of total sleep duration (HR, 2.26; 95% CI, 1.13-4.52; P =.021).

“This study provides novel evidence of the association between sleep duration and cancer incidence from both static and dynamic perspectives,” the researchers wrote.

They suggested several possible mechanisms for the association between sleep and cancer risk, including decreased melatonin levels, impaired immune function, and disruptions of circadian rhythms that could promote tumorigenesis.