A study led by Dr. Mengyu Fan published in the European Heart Journal showed that a healthy sleep pattern was associated with a lower risk of cardiovascular disease (CVD), congestive heart failure (CHF), and stroke in patients with low, intermediate or high genetic risk.
Cardiovascular disease is among the leading cause of mortality worldwide. There has been evidence to suggest that unhealthy sleeping behaviors, including short or long duration of sleep, insomnia, snoring, and excessive daytime sleepiness was associated with a 10-40% increased risk of cardiovascular disease. However, a lot of these sleeping behaviors typically correlate with each other. There is a lack of evidence surrounding the relationship of co-occurrence of sleeping behaviors and their impact on cardiovascular disease. Additionally, it is unknown whether genetic susceptibility can interact with lifestyle factors leading to changes in cardio-metabolic outcomes. The investigators aimed to utilize the United Kingdom Biobank Study to address this gap in knowledge.
The UK Biobank Study is a prospective study with 500,000 patients between the ages of 37 and 73. In this study, participants provided information on their sleep behavior and other health-related behaviors. Additionally, blood samples were collected for genotyping. Patients without cardiovascular disease were included in the analysis. Patients with missing data and those with cardiovascular disease at baseline were excluded from the study. Sleep behavior, including sleep duration, chronotype preference, reported snoring, and subjective daytime sleepiness, was collected. Based on their sleeping behavior, each patient received a sleep score (ranging from 0 to 5 with 5 being the healthiest sleep pattern). A score of 4 or more was considered healthy, 2 to 3 was intermediate, and a score of 1 or less was considered an unhealthy sleeping pattern. A genetic score was determined based on the presence of 74 independent single nucleotide polymorphism (SNP) and 10 SNPs that showed significant genome association with CHD and stroke. The genetic risk scores for CHD and stroke were calculated separately. Based on the genetic risk score, patients were divided into quintiles for each outcome. Using linked hospital data and death registry records, the primary outcome of CVD (a composite of CHD and stroke) was assessed. Additionally, CHD and stroke were assessed separately.
Of the 385,292 patients enrolled in this study, 21.8% had a healthy sleep score of 5, 37.0% had a score of 4, and 27.9% had a score of 3.0. Participants with a higher sleep score were more likely to have a lower body mass index, be female, smoke and be physically active and less likely to have chronic conditions such as hypertension or diabetes. During a median follow up of 8.5 years, a total of 7,280 patients met the CVD endpoint (including 4,667 cases of CHD and 2,650 strokes). Short (<6 h) or long sleep duration (>9 h), insomnia, snoring, and excessive daytime sleepiness were all associated with an increased risk of a CVD event. After adjusting for relevant baseline variables, with the exception of snoring, the association between the abnormal sleeping behaviors and CVD remained significant. Compared to those with a sleep score of 1 or less, the adjusted HRs (95% CI) of those with a sleep score of 5 was 0.65 (0.52–0.81) for CVD, 0.66 (0.56–0.78) for CHD, and 0.66 (0.58– 0.75) for stroke, respectively. Each additional healthy sleep score was associated with an 8% lower risk of CVD, a 9% lower risk of CHD, and a 7% lower risk of stroke. When looking at the interaction between genetic risk score and sleep score, while the interaction between the two was not significant, the investigators found that patients with the highest risk of CVD based on their genetic score and a poor sleep pattern had the highest risk of CHD and stroke.
Through this large prospective cohort, the investigators were able to demonstrate that poor sleeping behavior was associated with an increased risk of both CHD and stroke. Additionally, this association remained significant despite an individual’s genetic risk score. Although the interaction between sleeping behavior and genetic risk score on the outcome was not significant, patients with a high genetic risk score and poor sleeping behavior had the highest risk of a CVD event. The current study adds to the body of evidence that demonstrates an association between poor sleeping patterns and an increased risk of cardiovascular disease. When discussing the implications of this study, the investigators noted, “The healthy sleep pattern defined by this study (early chronotype, sleep 7–8 h per day, never or rarely insomnia, no snoring, and no frequent excessive daytime sleepiness) provides a positive frame of reference for sleep and is also of value in identifying high-risk individuals and facilitating health management. From a public health perspective, the use of the simple score algorithm makes epidemiological findings easier to be interpreted and translated into practice, and therefore to be more informative to the general population.” However, this study does have its limitations. The findings of this study are based on observational data and can be affected by confounding and unmeasured bias. Therefore, the findings should be interpreted with caution.