Every study we read on this question

Trials in people (1)

• Trial in 80 adults with overweight: sleep counseling lengthened sleep and cut food intake
  Randomized trial202280 peoplePoints to benefit

Population studies (11)

• Study that followed 406,584 adults: sleep links to digestive cancer death vanished after adjusting
  Population study: followed a group2025406,584 peopleMixed
• Follow-up study of 1,360 adults with diabetes: more sleep linked to less heart disease
  Population study: followed a group20251,360 peoplePoints to benefit
• Survey of 27,473 Taiwan adults: short sleep linked to higher odds of obesity
  Population study: one-time survey202527,473 peoplePoints to benefit
• Study of 13,078 Chinese adults: sleep under 5 hours linked to more heart disease
  Population study: followed a group202513,078 peoplePoints to benefit
• Study that followed 60,977 adults: sleep regularity predicted death better than sleep length
  Population study: followed a group202460,977 peopleNo difference
• Study that followed 502,383 adults: no clear sleep link to dementia after adjusting
  Population study: followed a group2024502,383 peopleNo difference
• Study that followed 195 adults for 1 year: short sleepers regained more weight
  Population study: followed a group2023195 peoplePoints to benefit
• Study that followed 1,216 teens: under 7 hours' sleep linked to overweight or obesity
  Population study: followed a group20231,216 peoplePoints to benefit
• Study that followed 25,430 Swedish adults: death risk lowest at 7 hours of sleep
  Population study: followed a group202225,430 peopleMixed
• Study that followed 322,721 Asian adults: lowest death risk at 7 hours of sleep
  Population study: followed a group2021322,721 peopleMixed
• Study that followed 461,347 adults: short and long sleep linked to more heart attacks
  Population study: followed a group2019461,347 peopleMixed

Blood and genes (1)

• Gene study of 404,044 adults: short-sleep genes linked to higher heart disease risk
  Gene study (Mendelian randomization)2021404,044 peoplePoints to benefit

Reviews (4)

• Pooled review: sleeping under 7 or over 8 hours linked to higher diabetes risk
  Pooled review (meta-analysis)2025Mixed
• Review of 69 pooled analyses: short and long sleep linked to higher death risk
  Systematic review2022Mixed
• Pooled review of 137 studies: long sleep linked to higher death and heart risk
  Pooled review (meta-analysis)20185,134,036 peoplePoints to harm
• Pooled review of 153 studies: short sleep linked to higher death and diabetes risk
  Pooled review (meta-analysis)20175,172,710 peoplePoints to benefit

Opinion (5)

• Review of insomnia and weight: short sleep linked to weight gain, other links inconsistent
  Opinion or narrative review2024Points to benefit
• Review of sleep studies: short sleep linked to obesity and type 2 diabetes risk
  Opinion or narrative review2021Points to benefit
• Review of studies: short and long sleep both linked to type 2 diabetes
  Opinion or narrative review2018Mixed
• Review of short sleep and overweight: evidence that sleep length causes obesity is insufficient
  Opinion or narrative review2016No difference
• Review of lab and population studies: short sleep linked to higher BMI, weight gain
  Opinion or narrative review2008Points to benefit