Overview

• An Uppsala University study in 16 healthy young men found that restricting sleep to about 4.25 hours for three nights increased inflammatory proteins linked to cardiovascular risk and blunted the usual beneficial response to exercise.
• These changes appeared within days under tightly controlled lab conditions with regulated diet, activity and light exposure, highlighting how quickly severe sleep loss can affect physiology.
• The American Heart Association now counts sleep as a core cardiovascular pillar and advises adults to target approximately seven to nine hours nightly.
• Harvard Health reports associations between sleeping more than nine hours or fewer than six and lower scores on tests of memory, attention and processing speed.
• Guidance emphasizes a cool, dark, quiet bedroom with appropriate mattress and pillows, while a small study suggests brief late afternoon resistance breaks may add about 29 minutes of sleep that night.