A recent study published in JAMA Network Open reveals that persistently favorable sleep patterns may reduce the risk of cardiovascular disease (CVD), even in individuals with higher genetic susceptibility.

Study: Changes in Sleep Patterns, Genetic Susceptibility, and Incident Cardiovascular Disease in China. Image Credit: aslysun / Shutterstock.com

How does sleep affect CVD?

CVD is a leading cause of morbidity and mortality worldwide, with about 33% of all deaths in 2019 attributed to CVD throughout the world. Similarly, the estimated mortality rate due to CVD in China currently exceeds 40%. Thus, the global burden of CVD emphasizes the importance of identifying modifiable risk factors that can be implemented to prevent CVD.

Growing evidence indicates that an unhealthy lifestyle, including impaired sleep patterns, can potentially increase the risk of CVD. Despite these studies, a single sleep measurement was often used to define sleep patterns, which may not adequately reflect sleep with CVD, as sleep habits can evolve. Furthermore, there remains a lack of data on how different sleep patterns in retired and older populations affect their risk of CVD.

Study design

The current study was conducted between 2008 and 2018 in China and included 15,306 middle-aged and older individuals without diagnosed cardiovascular complications. Self-reported sleep information was collected at baseline between 2008 and 2010 and at the first follow-up visit in 2013.

Sleep patterns of the study participants were defined as "favorable" and "unfavorable" based on bedtime, sleep duration, sleep quality, and midday napping. Study participants were categorized into four groups: persistent unfavorable, favorable-unfavorable (transitioning from favorable to unfavorable), unfavorable-favorable (transitioning from unfavorable to favorable), and persistent favorable.

Polygenic risk scores for coronary heart disease and stroke were calculated to determine the genetic susceptibility of the study participants to these diseases. Additionally, an expert panel of physicians was appointed to assess incident CVD, defined as a composite outcome of incident coronary heart disease and incident stroke, until the end of 2018.

Important observations

A total of 3,669 incident CVD cases, including 2,986 coronary heart disease cases and 683 stroke cases, were documented during the five-year study period from 2013 to 2018.

The assessment of five-year changes in sleep patterns found that 35.8% of participants practiced persistent unfavorable sleep patterns, whereas 25.8% had persistent favorable sleep patterns. Young age, female gender, and higher educational background were associated with persistent favorable sleep patterns.

Study participants with persistent unfavorable sleep patterns were at a greater risk of CVD than those with persistent favorable, favorable-unfavorable, or unfavorable-favorable sleep patterns. More specifically, a 16% and 34% reduced risk of coronary heart disease and stroke were observed among participants with persistent favorable sleep patterns. A subgroup analysis conducted after adjusting for participant's age and sex revealed similar associations between changes in sleep patterns and CVD risk.

Genetic risk factors were not found to significantly influence the association between sleep pattern changes and cardiovascular disease risk. However, a combination of sleep pattern changes and polygenic risk scores was associated with cardiovascular risk in a dose-dependent manner.

To this end, individuals with persistent favorable sleep patterns and an intermediate genetic risk had a 36% reduced risk of stroke. In contrast, those with persistent favorable sleep patterns and a high genetic risk had a 45% reduced risk of stroke. Further analysis revealed that participants with persistent favorable sleep patterns and low genetic risk had a 35% reduced risk of coronary heart disease and a 52% lower risk of stroke compared to those with persistently unfavorable sleep patterns and high genetic risk.

Conclusions

The current study found that individuals with persistent favorable sleep patterns were at the lowest risk of incident CVD, coronary heart disease, and stroke during the subsequent five years. The benefits of persistent favorable sleep patterns remain unchanged for those with high genetic susceptibility to cardiovascular complications, thus demonstrating that individuals with higher genetic risk may benefit from persistent favorable sleep patterns. 

Importantly, the study population included middle-aged and older Chinese retirees, which may restrict the generalizability of these findings. Furthermore, the current study does not include any information about participants' sleep disorders and depression levels, which may have confounded the observed associations.