Brighter Bedroom Light at Night Predicts Risk for Earlier Pubertal Onset: A 2-Year Longitudinal Study
Authors' conclusion
These findings suggest an accelerating effect of individual-level LAN exposure on pubertal onset in both boys and girls, particularly during the post-bedtime period.
Study context
- Population
- Boys and girls aged 6 to 10 years, Tianchang, Anhui province, China; bedroom light at night (LAN) recorded at 1-minute intervals for 2 nights with portable illuminance meter at baseline
- Participants
- 886 participants
- Exposure
- Highest vs lowest bedroom light at night exposure
- Outcome
- Pubertal onset (breast development in girls, testicular volume in boys), assessed every 6 months
- Follow-up
- 2 years
Methodological detailslongitudinal, 2-year follow-up
- Longitudinal
- 2-year follow-up
Main finding
As reported in the abstract
Timing of pubertal onset
Time ratio (TR)
0.96
95% CI 0.95–0.98
Boys; puberty started 3.84 months earlier
TR
0.96
95% CI 0.94–0.98
Girls; puberty started 4.12 months earlier
Observational data: associations, not effects.
Further findings
Earlier pubertal onset per 30-minute increase in duration of LAN ≥ 3 lx
- Earlier testicular development in boys, HR
- 1.09 (1.02-1.16) (95% CI)
- Earlier thelarche in girls, HR
- 1.12 (1.07-1.16) (95% CI)
Timing of LAN exposure
- Increased risk more pronounced with postbedtime than preawake light exposure
Original publication
Brighter Bedroom Light at Night Predicts Risk for Earlier Pubertal Onset: A 2-Year Longitudinal Study. J Clin Endocrinol Metab. Published 27 September 2025. doi:10.
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