In healthy adults, how much or how well you sleep doesn’t seem to affect your resting heart or stress system — at least when sleep is measured objectively, which might mean earlier findings were off.

For healthy adults, how well you sleep night after night — based on movement tracking — doesn't seem to affect your blood pressure, heart rate, or nervous system activity, even when we account for age, sex, and weight.

For healthy adults, how much you usually sleep doesn’t seem to affect your blood pressure, heart rate, or stress nerve activity — even if you sleep less than average.

If you sleep less than 7.7 hours a night, the less you sleep, the higher your body mass index (BMI) tends to be — for example, people who sleep 5 hours have a 3.6% higher BMI than those who sleep 8 hours, even when you account for their age, gender, or breathing issues during sleep.

After 24 hours without sleep, heart rate drops slightly but then starts rising again over the next 8 hours, suggesting the body's response to sleep loss changes over time.

Healthy sleepers show stronger sympathetic nervous system activity during sleep deprivation compared to those with chronic insomnia. This finding is from the abstract summary - full study details were not available