For the study, researchers analyzed sleep and health data on nearly 47,000 people 40 to 79. Participants entered the study between 2002 and 2009, and completed follow-up surveys between 2008 and 2013.
Researchers grouped all the participants based on their sleep “trajectory” — differences between the sleep they reported at the start and then during follow-up.
For example, people on a “long-short” trajectory got too much sleep at the beginning and too little by the end, while “short-long” went the opposite way.
Overall, 66% of participants reported getting too much or too little sleep, results show.