A regular sleep schedule is associated with lower weight, lower blood sugar levels, and a lower risk of heart disease and diabetes—findings that affirm that sleep regularity has a greater influence on health than sleep duration and timing, according to an ongoing study in Scientific Reports.
A person has good sleep regularity, or sleep hygiene, when he or she goes to bed and wakes up at the same time, every day of the week. Scheduled sleeping regulates the body's circadian rhythm as well as appetite and digestion, Carolyn Crist writes for Reuters.
Researchers track and analyze 2,000 sleep schedules
For the study, researchers tracked the sleep schedules of almost 2,000 adult participants using the Sleep Regularity Index, a metric that assesses sleep variation from one day to the next to estimate regular sleep and wake up times, including naps.
For one week, the participants, who averaged 69-years old, wore a wrist device that measured and recorded light exposure, physical activity, as well as sleep and wake indicators. The participants also recorded their sleep and wake times and daytime sleepiness in a sleep diary.
The researchers monitored participants' psychiatric health by assessing the severity of depressive symptoms. Participants were also assessed for cardiovascular disease risk factors, including low and high cholesterol levels, diabetes, and hypertension.
Poor sleep hygiene increases obesity and heart disease risk
According to the study, adults with irregular sleep schedules experienced more daytime sleepiness and slept more during the day—and less at night—than regular sleepers. Irregular sleepers also went to bed later than regular sleepers and experienced less light exposure.
Overall, the researchers found an association between sleep irregularity and a heightened 10-year risk of heart disease, as well as increased severity of depressive symptoms—which are themselves linked to an increased risk of heart disease. Further, the irregular sleepers had a greater risk of hypertension, diabetes, and obesity than regular sleepers.
Adults should establish a regular sleep schedule, according to researchers
Jessica Lunsford-Avery of Duke University Medical Center, who was the lead author of the study, said the results "underscore ... the importance" of a regular sleeping schedule. She explained, "Among the three types of sleep problems—duration, regularity, and timing as a morning lark or night owl—sleep regularity was the most consistently and strongly associated with health."
Lunsford-Avery added that "irregular sleep patterns are common in people of all ages," but poor sleep hygiene is most common among "older adults who have left the work force," people who work at odd or late hours, and African-Americans.
Further research is needed to observe the cause-and-effect relationships between disease risks and sleep irregularity, Lunsford-Avery said, noting she and her colleagues plan to continue assessing disease risk factors as part of the study.
Separately, Frank Scheer, director of the Medical Chronobiology Program at Brigham and Women’s Hospital, who wasn't involved in the study, said of the research, "The exciting findings include the question, 'What can we do about it?'" He explained, "In the broader sense, a regularity in bedtime and wake time is key … Fundamental mechanisms are at play, so if we can think about ways to get the best sleep and keep a regular bedtime, it may be one of the most important pieces of advice for good sleep hygiene" (Crist, Reuters, 9/27; Scientific Reports study, 9/21).
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