Browse evidence-based analysis of health-related claims and assertions
Log in to see full claim details, scientific mechanisms, and cited studies.
In women during pregnancy and after childbirth, fluctuations in sleep quality from their own normal pattern are linked to a stronger rise in the stress hormone cortisol upon waking, with greater...
People who smoke report sleeping just as well as non-smokers, even though objective measurements show their sleep is more disrupted with more time spent awake during the night.
In people who smoke, higher levels of the stress hormone cortisol are linked to spending less time awake after falling asleep, suggesting cortisol may reduce sleep disruptions caused by smoking,...
Adults who smoke tobacco tend to have higher levels of the stress hormone cortisol and spend more time awake during the night after initially falling asleep, compared to adults who do not smoke.
Taking 25 mg of prednisolone daily for five days in healthy young men raises the level of active glucocorticoid hormones in the blood by 4.5 times compared to taking a placebo.
Taking 25 mg of prednisolone daily for five days lowers sleep efficiency by about 3 percentage points in healthy young adult males, compared to taking a placebo.
Taking 25 mg of prednisolone daily for five days raises nighttime systolic blood pressure by about 7 mmHg in healthy young men compared to a placebo, which reduces the normal drop in blood pressure...
Taking 25 mg of prednisolone daily for five days raises glucose levels in the body at night by 67% compared to daytime levels in healthy young men, suggesting that the drug interferes with the...
Taking 25 mg of prednisolone daily for five days reduces the natural daily fluctuations in the activity of key clock genes in muscle and fat tissue, suggesting the drug directly interferes with the...
For hospitalized adults with depression, exposure to bright light each day lowers the daily fluctuation in cortisol levels by about 1.27 ng/mL compared to exposure to dim light.
For people with depression in the hospital, using bright light therapy for two weeks reduces their depression symptoms more than dim light, as measured by standard clinical scales.
In hospitalized adults with depression undergoing bright light therapy, decreases in blood sugar levels are linked to decreases in the average level of cortisol over a 24-hour period, suggesting that...
For hospitalized adults with depression, exposure to bright light each day lowers the average level of cortisol in the body over a 24-hour period by about 1.37 ng/mL compared to dim light, suggesting...
In hospitalized adults with moderate to severe depression, daily exposure to bright light for 30 minutes over two weeks is associated with a measurable decrease in fasting blood glucose levels...
In athletes undergoing intense training, differences in sleep quality are not clearly linked to whether they compete in athletics or other sports once you account for their cortisol levels,...
Among athletes with intense training schedules, differences in sleep quality are not reliably linked to whether someone is male or female, or to their age, once cortisol levels are taken into account.
Athletes who sleep poorly are more likely to have elevated cortisol levels than those who sleep well, even when accounting for differences in sport, gender, and age. This suggests cortisol levels may...
In elite athletes training for national competitions, a blood cortisol level of 208.05 nmol/L or higher is associated with a 75% chance of correctly identifying poor sleep quality and a 71.9% chance...
In athletes with high levels of the stress hormone cortisol, there is a measurable link to worse sleep quality, as determined by a standard sleep questionnaire.
In healthy adults who slept only six hours for two nights, exposure to blue light in the morning helped maintain cognitive function, while light that mimicked dawn improved it further, compared to...
After two nights of limited sleep, people exposed to light that mimics a natural sunrise have higher cortisol levels when they wake up compared to those exposed to blue light or dim light.
In healthy adults who have had limited sleep for two nights, exposure to blue light in the morning may shift the timing of melatonin release to occur earlier than when exposed to dawn-like or dim...
In healthy adults who have had limited sleep, exposure to a simulated sunrise light before waking may improve how good they feel, compared to exposure to dim light or blue light.
Different colors of light affect the body's internal clock differently; blue light at a specific wavelength strongly activates circadian pathways, while red light at another wavelength has minimal...