Time for lights out: artificial light during sleep linked to weight gain

  • JAMA Intern Med

  • International Clinical Digest
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Takeaway

  • Exposure to artificial light while sleeping increased risk for weight gain and obesity, especially among women in this cohort study.

Why this matters

  • Exposure to artificial light during sleep should be addressed in discussions about obesity prevention.

Key results

  • Exposure to any artificial light at night was linked to increased baseline (prevalence ratios; 95% CIs): 
    • Obesity: 1.03 (1.02-1.03),
    • Waist circumference: 1.12 (1.09-1.16),
    • BMI: 1.03 (1.02-1.04),
    • Waist-hip ratio: 1.04 (1.00-1.08), and
    • Waist-height ratio: 1.07 (1.04-1.09).
  • Compared with no light on, having on the TV or a light was linked to (relative risks; 95% CIs): 
    • Gaining 5 kg or more: 1.17 (1.08-1.27; Ptrend<.001>
    • BMI increase ≥10%: 1.13 (1.02-1.26; Ptrend=.04), and
    • Incidence overweight and obesity: 1.22 (1.06-1.40; Ptrend=.03) and 1.33 (1.13-1.57; Ptrend<.001 respectively.>
  • The association was stronger for women with baseline normal weight or overweight than among women with obesity.

Study design

  • Prospective analysis of data for 43,722 women ages 35-74 years, enrolled in US Sister Study, July 2003-March 2009.
  • Funding: NIH. 

Limitations

  • No way to track change in artificial light exposure over time, intensity, wavelength, other factors; exposures were self-reported.