The Effect of Sleep Deprivation and Disruption on DNA Damage and Health of Doctors

DNA damage and repair are dynamic processes
Animal studies have shown that sleep loss can induce genetic damage in different organs
Sleep deprivation is known to induce oxidative stress
Most studies are conducted on older adults, and these results may not be extrapolated to a younger workforce
Studies of sleep deprivation and its effect on DNA damage in younger people are lacking

Cross‐sectional observational study on 51 healthy, full‐time doctors
Assigned into 2 groups:
- On call group worked at least 3 night shifts/month
- Control group were full-time clinicians who did offsite on calls or no on calls
  - Majority no on calls for 3-5 years
  - Offsite on calls – travelled back 1-2 times per month after midnight

2 doctors were excluded from analysis as they later admitted to taking dietary suppression pills
There was significantly reduced expression of DNA repair genes in doctors who regularly worked night shifts, both at baseline and following a single night of sleep deprivation

The DNA repair genes, ERCC1, OGG1 and XRCC1, examined in this study are involved in nucleotide excision repair, base excision repair and recombinational repair
Decreased or absent expression of these genes is associated with accumulation of DNA damage, increased rates of mutation and tumour genesis
Significantly lower baseline OGG1 and ERCC1 expression, and decreases in expression of all three genes investigated after acute sleep deprivation, suggest impairment of DNA repair activity in sleep‐deprived people
Disrupted circadian rhythm and suppression of nocturnal melatonin causes altered endogenous sex hormone balance, de-synchrony of clock genes and the expression of genes implicated in cancer development
Heightened neuroendocrine stress responses, higher glucocorticoid and catecholamine levels, disrupted appetite control, pro‐inflammatory responses, immunosuppression and changes in lifestyle, including diet and physical activity, are implicated

Results could have been confounded by other factors, including greater work stress in specialties with on‐site calls, different occupational risk exposure (e.g. to radiation) between specialties.
Sleep adequacy and acute sleep deprivation was self‐defined
Sleep demand and habits can vary greatly between individuals, and in addition to the number of hours slept, sleep quality is also an important factor determining sleep adequacy
Participants were mostly young Chinese doctors, and therefore the results of this study may only be applied to this population
The genomic consequence of sleep deprivation and disruption may vary as a function of ethnicity, locality and age groups
Only doctors in the study-not the only profession who work night shifts
Self reporting of adequacy of sleep
Longitudinal study would be more useful- following DNA repair genes in the period before on calls and following the commencement of overnight on calls

Summary by Dr S Sethi. Journal Club Meeting 31 January 2019.