A graph of how long Americans sleep forms a U-shaped pattern across our lives, with age 40 being the low point and hours of sleep starting to creep back up about age 50, Medical College of Georgia investigators report.
Our sleep efficiency, which basically means how much of the time we devote to sleeping that we actually sleep, tends to decrease across our lifetime, but investigators were surprised to find efficiency stabilized from ages 30 to 60, says Dr. Xiaoling Wang, genetic epidemiologist at MCG’s Georgia Prevention Institute and corresponding author of the study in the journal Scientific Reports.
True sleep time is tough to measure in a large database of individuals who provide a representative sample of the country, particularly since most assessments are self-reports of sleep, says first author, Dr. Shaoyong Su, also a genetic epidemiologist at the Georgia Prevention Institute and the study’s first author.
The main innovations in the study include its representative sampling technique, broadly inclusive age and the use of accelerometers to measure movement and get a more objective idea of how much participants slept.
For this study, investigators used what is considered a representative sample of 200 million Americans: 11,279 participants age 6 and older from the National Health and Nutrition Examination Survey, or NHANES, which focuses on different populations or health topics. Data on these participants was collected from 2011-14 but released in late 2020, and this is the first time that 24-hour accelerometer data was available in a nationally representative sample.
Participants wore accelerometers on their nondominant wrist 24-hours a day for seven consecutive days. While the device does not directly measure sleep time, the premise is that measuring movement gives you some indication of whether you are asleep or not, says coauthor Dr. Vaughn McCall, chair of the MCG Department of Psychiatry and Health Behavior and an expert in the trifecta of insomnia, depression and suicide.
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