Scientists put cold germs in people's noses. On purpose!

Observational study. 164 people. 1 week of wrist actigraphy + sleep diary in the ~2 months before exposure, then 6 days hotel quarantine (5 days of monitoring after the nasal drops); blood test ~28 days after exposure. Data collected 2007-2011.

The scientists only watched the habit. Nobody was told what to do. A clue, not proof.

Who: Healthy volunteers from the Pittsburgh (USA) area, 94 men and 70 women aged 18-55 (mean 29.9), screened for good health (no chronic illness, no regular medication, no sleep apnea, no psychiatric medication, low prior antibodies to the virus); paid $1,000

• Slept 6 hours or lessMorecolds
• Slept more than 6 hoursFewercolds

6 hours of tracked sleep or less: about 4× the odds of catching the cold vs over 7 hours

Nobody was told how long to sleep.

More to know, from our read of the paper:

• Sleep was measured, not manipulated: association, not causation. The authors say the design rules out reverse causation (sleep was measured before exposure) but 'does not provide direct evidence of causality'
• Small study: 164 people, 48 colds; the reference group (> 7 h) had only 22 people, so the odds ratios have very wide confidence intervals (OR 4.50, 95% CI 1.08-18.69; OR 4.24, 1.08-16.71)
• Only one week of sleep measured; actigraphy is a wrist movement measure of rest/activity, not a direct measure of sleep (authors' own caveat)
• Very selected sample: healthy adults 18-55 screened for good health, no regular medications, no sleep disorders, low prior antibodies; one virus strain (rhinovirus 39) given as nasal drops in a hotel quarantine. Not tested in older adults or people with sleep disorders
• No sleep intervention was tested: whether sleeping more protects you is, in the authors' words, 'an open question'

164 healthy adults (18–55) wore a sleep watch for a week. Then scientists dripped cold germs into their noses and kept them in a hotel for 5 days. People who slept 6 hours or less caught colds more often than people who slept over 7 hours (about 4 times the odds). What people wrote in their sleep diary did not show who got sick. Nobody was told how long to sleep (the virus was given on purpose, the sleep was only watched), so this is a clue, not proof.

We read the abstract and the full text of this paper and checked every number on this page against it (18 facts, checked on 2026-10-03). The study design is named above. Cohort and other observational studies are described as linked, not proven. Found an error? Email theis@onestudyaday.com.