Wang YH, Wang J, Chen SH, et al. Association of longitudinal patterns of habitual sleep duration with risk of cardiovascular events and all-cause mortality. JAMA Netw Open. 2020;3(5):e205246.
To determine whether trajectories of long-term vs single-measure sleep duration are associated with subsequent risk of CVEs and all-cause mortality
Prospective, population-based cohort study
52,599 Chinese adults (76.2% male, 23.8% female) without atrial fibrillation, myocardial infarction, stroke, or cancer. The mean [SD] age at baseline for all participants was 52.5 [11.8] years.
Study Parameters Assessed
Trajectories in sleep duration from January 1, 2006, to December 31, 2010, were identified to investigate the association with risk of CVEs and all-cause mortality from January 1, 2010, to December 31, 2017. Habitual self-reported nocturnal sleep durations were collected in 2006, 2008, and 2010. Trajectories in sleep duration for 4 years were identified by latent mixture modeling.
Subjective, habitual, nighttime sleep duration was biennially collected during face-to-face interviews with the question, “On average, how many hours of sleep have you gotten per night in the preceding 12 months?”
Primary Outcome Measures
All-cause mortality and first incident CVEs (including fatal or nonfatal CVEs, including atrial fibrillation, myocardial infarction, and stroke).
Based on the baseline sleep duration and patterns over time, 4 sleep trajectories were categorized as:
- normal stable
- normal decreasing
- low increasing
- low stable
Sleep duration trajectories were significantly associated with the risk of CVEs and all-cause mortality.
Compared with the normal-stable group, who maintained a sleep duration of 7.0 to 8.0 hours per night for 4 years, low-stable and low-increasing patterns were significantly associated with higher risk of first CVEs after adjustment for potential confounders.
Adjusted hazard ratios (HRs) of CVEs for each pattern were:
- low-increasing: 1.22 (95% CI, 1.04-1.43)
- normal-decreasing: 1.13 (95% CI, 0.97-1.32)
- low-stable: 1.47 (95% CI, 1.05-2.05)
Compared to volunteers in the normal-stable group, the risk of all-cause mortality was significantly higher in those with normal-decreasing and low-stable sleep duration patterns.
Adjusted HRs of death for each pattern were:
- normal-decreasing: 1.34 (95% CI, 1.15-1.57)
- low-increasing: 0.95 (95% CI, 0.80-1.13)
- low-stable: 1.50 (95% CI, 1.07-2.10)
Results were consistent even when potential confounding variables were excluded, including outcomes that occurred in the first 2 years of follow-up, in shift workers, in those who developed cancers during follow-up, in those with self-reported frequent snoring, or in volunteers with atrial fibrillation.
No significant interaction was observed for any of the medical comorbidities, and the results were similar when stratified by baseline weight status and sex.
However, when stratified by age group, the association with CVEs was found for the low-stable (HR, 1.75; 95% CI, 1.17-1.62) and low-increasing (HR, 1.28; 95% CI, 1.04-1.56) groups among participants younger than 65 years, but not among those 65 years or older.
Participants with sleep duration of 7.0 to 8.0 hours per night had the lowest risk of all outcomes. After adjustment for potential confounders, short and long sleep durations were associated with CVEs and death.
Compared with sleeping 7.0 to less than 8.0 hours per night, adjusted HRs for the composite outcomes were 1.24 (95% CI, 1.10-1.39) for those who slept less than 6.0 hours per night, 1.08 (95% CI, 0.98-1.20) for those who slept 6.0 to less than 7.0 hours per night, 1.32 (95% CI, 1.21-1.44) for those who slept 8.0 to less than 9.0 hours per night, and 1.45 (95% CI, 1.13-1.87) for those who slept at least 9.0 hours per night. The results were similar for CVEs and all-cause mortality individually.
Sleep deprivation is a major contributor to chronic diseases and early mortality. It’s estimated that 50 to 70 million Americans chronically suffer from a disorder of sleep and wakefulness.1 Undoubtedly clinicians are working with patients struggling with sleep issues. The prevalence of insomnia in primary care patients is estimated as high as 69%.2
This study is the first to evaluate the association of changes in sleep patterns with cardiovascular events and mortality. The results suggest that trajectories in sleep duration are clinically important variables to evaluate when assessing risks for a first cardiovascular event and death. Since the results were maintained even after adjustment for a single measure of baseline sleep duration, the current research builds on a body of prior evidence showing that single measures of sleep duration are also associated with adverse health outcomes.
Prior research has evaluated the comorbidities and mortality associated with chronic sleep deprivation. Inadequate sleep is a correlate of virtually all psychiatric disorders and presages specific disorders such as depression and substance abuse. Insomnia is also associated with a diminished quality of life, the magnitude of which is similar to chronic conditions such as congestive heart failure and major depressive disorder3,4 and is considered an early symptom of Alzheimer’s disease, Parkinson disease, and Huntington disease.5
Inadequate sleep is a correlate of virtually all psychiatric disorders and presages specific disorders such as depression and substance abuse.
Sleeping less than 6 hours per night on average has been associated with double the risk for high blood pressure. Men who are short sleepers were also at 4 times greater risk for dying early. Short sleepers and long sleepers, which are people who sleep more than 9 hours per night on average, are both at increased risk for metabolic syndrome and diabetes.6-10
A prior study published in 2010 in the journal Sleep, concluded that increased early mortality was associated with male short sleepers but not female.9 In contrast to that earlier study, the current one found an increase in all-cause mortality in both male and female volunteers who exhibited the low-stable and normal-decreasing sleep trajectories.
The current study provides clinically relevant data that can inform how clinicians evaluate their patients. In addition to asking patients how many hours they sleep on average per night, understanding changes in sleep patterns over time may provide a more comprehensive picture of risk for first cardiovascular events and death.
Conducting additional research to confirm these results and also expand the endpoints to additional outcomes, such as diabetes, hypertension, and cancer would add to our knowledge of the health impacts of sleep and changes in sleep patterns over time.