Researchers at Brigham and Women’s Hospital in Boston have found that going to sleep at different times each night may double a person’s risk of developing heart disease.
Tianyi Huang, the study’s lead author, said, “When we talk about interventions to prevent heart attacks and stroke, we focus on diet and exercise. Even when we talk about sleep, we tend to focus on duration -- how many hours a person sleeps each night -- but not on sleep irregularity and the impact of going to bed at different times or sleeping different amounts from night to night. Our study indicates that healthy sleep isn't just about quantity but also about variability, and that this can have an important effect on heart health."
For the study, the researchers examined data from the Multi-Ethnic Study of Atherosclerosis (MESA), which included health records from 1,992 people who did not have heart disease at the beginning of data-collection. With each participant aged between 45 and 84, they came from diverse ethnic backgrounds: 38% were white, 28% African AMerican, 22% Hispanic and 12% Chinese American.
To collect the data, each participant was given an activity tracker to wear on their wrists for seven days at various intervals over a 5-year period to record their sleep patterns, including bedtime, sleep duration and wake-up time. Over the study period, 111 participants experienced cardiovascular events, including heart attacks and strokes.
To analyze the data, the researchers split the participants into four groups. One group contained people with irregular sleeping patterns of two hours or more in sleep duration each night. Another group contained those with less than an hour variation in sleep duration per night, while the remaining two contained those with 30 minute and 90 minutes variations.
In the end, the researchers found that those with the most irregular sleep patterns were twice as likely to have a cardiovascular event than those with more regular sleeping habits. They estimated that while only 8 of every 1000 people following regular sleeping patterns would have a cardiovascular event each year, for those with the most irregular sleeping patterns, this figure would be 20.
Huang said, “Sleep regularity is a modifiable behavior. In the future, we'd like to explore whether changing one's sleep patterns by going to bed consistently each night may reduce a person's risk of future cardiovascular events.”