Sleep Duration vs. Cold Susceptibility

1. fewer than 6 hours of sleep

1.1. larger risk of getting sick

2. greater than 6 hours of sleep

2.1. smaller risk of getting sick

3. greater than 9 hours of sleep

3.1. increased risk of disease

4. What are the mechanisms that might link sleep and susceptibility to acute infectious illness?

4.1. Sleep, along with circadian rhythms, exerts substantial regulatory effects on the immune system

4.2. Circulating immune cells, including T and B cells, peak early in the night and then decline throughout the nocturnal hours moving out of circulation into lymphoid organs where exposure to virally infected cells occur

5. Illness expression in colds is generally attributed to blunted downregulation of local inflammatory responses

5.1. Emerging evidence demonstrates bidirectional links between sleep and inflammation

5.2. Proinflammatory activity has a role in the homeostatic regulation of sleep

6. S

7. Self-reported Sleep Diary

7.1. Less stable averages

7.2. Less accurate estimates of sleep

8. Wrist actigraphy

8.1. Well correlated with polysomnography

8.2. actigraphy assessed indices of sleep duration cannot identify specific dimensions of sleep (e.g., decreased slow wave sleep) that may be contributing to infectious risk

9. Future Studies

9.1. Include both the self-reported sleep diary and the wrist actigraphy

9.1.1. to understand when and why certain sleep measures significantly predict immune function

10. Recent evidence suggests that elevated systemic inflammation mediates prospective associations between short sleep duration and premature mortality

11. Future studies characterizing the immunologic mediators of cold incidence in the context of sleep duration and our viral challenge paradigm are needed to clarify when in the infection process sleep has the most potent effects

12. This study does not provide direct evidence of causality, the prospective nature of the viral challenge design does eliminate concerns of reverse causation.