Sleep Saves Lives: Lower Quantities of REM Sleep Tied to Mortality

Less rapid eye movement (REM) sleep appears to be associated with an increased risk of mortality among middle-aged and older adults, according to recent findings published in JAMA Neurology.

Investigators arrived at their conclusion after performing a cross-sectional study (N = 4050) of 2 independent cohorts: the Outcomes of Sleep Disorders in Older Men Sleep Study (n = 2675) and Wisconsin Sleep Cohort (n = 1375). The present analysis was performed from May 2018 to December 2019. The main outcome was defined as all-cause and cause-specific mortality validated by death certificates.

Specifically, the results of the study indicated that lower amounts of REM sleep were associated with an increased risk of all-cause, cardiovascular, and other noncancer-related mortality in both cohorts. Neurology Learning Network discussed these findings and their implications further with study author Eileen Leary, PhD, RPSGT, who performed this work while at the Stanford University Center for Sleep Sciences and Medicine in Palo Alto, California.

Neurology Learning Network: You and your colleagues concluded that a decreased percentage of REM sleep was associated with greater risk of all-cause, cardiovascular, and other noncancer-related mortality. Could you elaborate on this finding and its significance?

Dr Leary: Sleep is a complex biological phenomenon, and we are only just beginning to understand the consequences of insufficient and poor-quality sleep. Although previous studies identified there was a U-shaped association between sleep duration and mortality, little was known about how the different sleep stages relate to timing or cause of death.

The goal of this study was to investigate the relationship between REM sleep and mortality. A combination of traditional statistics and machine learning were used to conduct a thorough analysis on the association and explore whether another sleep stage could be a better predictor of mortality. The hypotheses were:

  • Lower quantities of REM sleep would be associated with increased mortality rates.
  • Compared with other sleep stages, REM would be the best predictor of mortality.

To evaluate generalizability of the findings, the final models were replicated in an independent cohort. Our research study found a strong association between lower levels of REM sleep and increased rate of mortality. We examined two cohorts and found that middle-aged and older adults in the studies had a 13% to 17% higher mortality rate for every 5% reduction in REM sleep. REM sleep was found to be the most important sleep stage for predicting mortality based on results from multiple analytic strategies. Therefore, it is unlikely the association was caused by a different sleep stage.

Given the complex underlying biological functions at play, further studies are required to understand whether this relationship is causal. However, the consistency of the association across different populations and sensitivity analyses (subpopulations) suggests that REM sleep may be a reliable predictor of mortality and may have other predictive health values.

Strategies to preserve REM sleep may influence clinical therapies and reduce mortality risk, particularly for adults with less than 15% REM sleep. While it would be premature to make any clinical recommendations based on this study, the results support the critical role sleep plays in health outcomes.

NLN: The American Academy of Sleep Medicine (AASM) recently issued a recommendation to end daylight saving time, noting that sleep deprivation associated with the time change leads to an increased risk of automobile accidents and patient safety-related adverse events. Does this study provide further evidence for the AASM’s recommendation?

Dr Leary: I agree with the AASM’s recommendation to permanently adopt standard time, and my research on the association between REM and mortality supports this position. There is a known circadian component to REM sleep, as most of REM occurs in the final third of the sleep period, so the quantity of REM sleep is significantly impacted when sleep duration is truncated by awakening early. When we shift the clocks back, we are impacting quantities of REM sleep while the body adjusts to the new schedule. There have been countless other studies demonstrating the negative impact of the time change on health and safety, so it is confusing to me why this practice is still in effect.

NLN: What areas of future research are still needed in this field?

Dr Leary: Since publishing this study, I was able to replicate the results in a third cohort, which strengthens the validity of the finding. A meta-analysis of the 3 cohorts produced an overall hazard ratio of 1.13 for all-cause mortality and 1.10 for cardiovascular mortality. When stratified by gender, the rate of mortality was similar for men and women (hazard ratio 1.14 vs 1.11). In sum, lower levels of REM sleep was an indicator of increased mortality rate across both genders and a broad age range.

Understanding how much within-subject variation is present over time and whether that change is associated with mortality will be an important addition to the REM/mortality story. The 3 cohorts used in these analyses have at least 1 additional visit with sleep study data. Therefore, the relative change in REM sleep over time can easily be determined. Even if the finding shows there is no association between change in REM sleep and mortality, the results will be informative.

NLN: What key takeaways about this topic do you hope to leave with neurologists and neurology providers?

Dr Leary: Numerous studies have linked insufficient sleep with significant health consequences, yet many people ignore the signs of sleep problems or do not allow enough time to get adequate sleep. In our busy, fast-paced lives, sleep can feel like a time-consuming nuisance. This study published in JAMA Neurology found that lower levels of REM sleep were associated with higher rates of mortality in 2 independent cohorts.

If you would like to speak with Dr Leary about this research, she may be contacted at eileen@eileenleary.com.

—Christina Vogt

Reference:
Leary EB, Watson KT, Ancoli-Israel S, et al. Association of rapid eye movement sleep with mortality in middle-aged and older adults. JAMA Neurol. 2020;
77(10):1241-1251. doi:10.1001/jamaneurol.2020.2108