Long Term exposure to high-intensity outdoor light at night linked to Diabetes Prevalence

Researchers from China found that chronic exposure to higher-intensity outdoor Light at night (LAN) increases the prevalence of Diabetes due to an increased risk of impaired homeostasis. The study was published in the journal Diabetologia. 

Diabetes is a global pandemic and out of the many risk factors, one of them is exposure to artificial light at night (LAN) as it might disrupt the circadian timing system. Hence researchers from China conducted a study called The China Noncommunicable Disease Surveillance Study. It was a national representative study conducted to estimate the associations of chronic exposure to outdoor LAN with glucose homeostasis markers and diabetes prevalence based on a national and cross-sectional survey of the general population in China in 2010.

 From 162 study sites across mainland China, nearly 98,658 participants aged ≥18 years who had been living in their current residence for at least 6 months were recruited. Diabetes was defined as per the ADA criteria. Using the satellite data outdoor LAN exposure was estimated and the participants attending each study site were assigned the same mean radiance of the outdoor LAN at the study site. The relationships between LAN exposure and markers of glucose homeostasis were assessed using linear regression incorporating a restricted cubic spline function. Cox regression with a constant for the time variable assigned to all individuals and with robust variance estimates was used to assess the associations between the levels of outdoor LAN exposure and the presence of diabetes by calculating the prevalence ratios (PRs) with adjustment for age, sex, education, smoking status, drinking status, physical activity, family history of diabetes, household income, urban/rural areas, taking antihypertensive medications, taking lipid-lowering medications, and BMI. 

Study findings: 

• The mean age of the study population was 42.7 years, and nearly 53,515 participants were women.
• There were a positive correlation between outdoor LAN exposure levels and HbA1c, fasting and 2 h glucose concentrations, and HOMA-IR. 
• A negative association was found between outdoor LAN exposure and HOMA-B.
• Diabetes prevalence was significantly associated with per-quintile LAN exposure (PR 1.07 [95% CI 1.02, 1.12]).
• There was a significant association between the highest quintile of LAN exposure and an increased prevalence of diabetes compared with the lowest quintile of exposure. 

Thus, the present study shows evidence that LAN is detrimental to health, and it is a potential novel risk factor for diabetes due to the increased risk of impaired glucose homeostasis with chronic exposure to LAN. 

Further reading: https://doi.org/10.1007/s00125-022-05819-x

Zheng, R., Xin, Z., Li, M. et al. Outdoor light at night in relation to glucose homeostasis and diabetes in Chinese adults: a national and cross-sectional study of 98,658 participants from 162 study sites. Diabetologia (2022).