Exposure to light at night (LAN) and risk of obesity: A systematic review and meta-analysis of observational studies

Ka Yan Lai; Chinmoy Sarkar; Michael Y Ni; John Gallacher; Chris Webster

doi:10.1016/j.envres.2020.109637

Exposure to light at night (LAN) and risk of obesity: A systematic review and meta-analysis of observational studies

Environ Res. 2020 Aug:187:109637. doi: 10.1016/j.envres.2020.109637. Epub 2020 May 12.

Authors

Ka Yan Lai¹, Chinmoy Sarkar², Michael Y Ni³, John Gallacher⁴, Chris Webster¹

Affiliations

¹ Healthy High Density Cities Lab, HKUrbanLab, The University of Hong Kong, Knowles Building, Pokfulam Road, Pokfulam, Hong Kong Special Administrative Region, China.
² Healthy High Density Cities Lab, HKUrbanLab, The University of Hong Kong, Knowles Building, Pokfulam Road, Pokfulam, Hong Kong Special Administrative Region, China; School of Public Health, The University of Hong Kong, Patrick Manson Building, Sassoon Road, Pokfulam, Hong Kong Special Administrative Region, China. Electronic address: csarkar@hku.hk.
³ Healthy High Density Cities Lab, HKUrbanLab, The University of Hong Kong, Knowles Building, Pokfulam Road, Pokfulam, Hong Kong Special Administrative Region, China; School of Public Health, The University of Hong Kong, Patrick Manson Building, Sassoon Road, Pokfulam, Hong Kong Special Administrative Region, China; The State Key Laboratory of Brain and Cognitive Sciences, The University of Hong Kong, Hong Kong Special Administrative Region, China.
⁴ Department of Psychiatry, Oxford University, Warneford Hospital, Oxford, UK.

PMID: 32497902
DOI: 10.1016/j.envres.2020.109637

Abstract

Background: There is emerging evidence of the association between light at night (LAN) exposure and weight gain.

Objective: We aim to conduct a systematic review and meta-analysis of observational studies on the association between LAN exposure and risk of obesity in human subjects.

Methods: Peer-reviewed observational studies were systematically searched from MEDLINE (EBSCO), Academic Search Complete (EBSCO), CINAHL Plus (EBSCO) and PubMed up to December 24, 2019. Random-effects models were developed to estimate the associations between LAN exposure and weight-related outcomes of overweight and obesity as measured by body mass index (BMI), waist circumference, waist-hip-ratio and waist-to-height-ratio. The I² statistic was used to assess the degree of heterogeneity across studies. The National Toxicology Program's Office of Health Assessment and Translation (OHAT) risk of bias rating tool and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) guideline were respectively employed to assess the risk of bias and to appraise the quality of the generated evidence.

Results: A total of 12 studies (three with longitudinal and nine of cross-sectional design) published between 2003 and 2019 were included for systematic review, while seven of them fulfilling the inclusion/exclusion criteria were included in the meta-analysis. A higher LAN exposure was significantly associated with 13% higher odds of overweight (BMI≥25 kg/m²) (Summary Odds Ratio; SOR: 1.13, 95% CI: 1.10-1.16) with low heterogeneity (I² = 27.27%), and 22% higher odds of obesity (BMI≥30 kg/m²) (SOR: 1.22, 95% CI: 1.07-1.38) with substantial heterogeneity (I² = 85.96%). Stratifying analyses by the levels of measurement of LAN exposures (macro-, meso- and micro-levels) and time of LAN measurement (including before and while sleeping) consistently produced robust estimates, with higher exposure to LAN being positively associated with poorer weight outcomes. Assessment of risk of bias identified substantial detection bias for exposure, with over half of the pooled studies employing subjective LAN measures. The overall evidence of the association between LAN exposure and risk of obesity was rated as 'moderate' as per the GRADE guideline.

Conclusions: Exposure to LAN was reported to be a significant risk factor for overweight and obesity. Prospectively designed future studies with objectively measured multi-level LAN exposures and weight outcomes are required.

Keywords: Body mass index; Light at night; Meta-analysis; Obesity.

Publication types

Meta-Analysis
Research Support, Non-U.S. Gov't
Systematic Review

MeSH terms

Body Mass Index
Body Weight
Circadian Rhythm
Cross-Sectional Studies
Humans
Light* / adverse effects
Obesity* / epidemiology
Overweight*