Human research · Observational

Wallace DA et al., JAMA Network Open 2024

Landmark T03 #1, what came after (2): a group with NO author overlap with the landmark (though Wallace, Redline and Sofer sit in the same Brigham and Women's Division of Sleep and Circadian Disorders / Harvard Division of Sleep Medicine as landmark co-authors Burns, Saxena and Lane - authorship independent, institution not), in a different population, device and metric, tested the day-light-and-mood half of the finding; the letter cites the landmark (ref 3). Wallace et al. 2024 (JAMA Network Open research letter; read in full) analysed 6,639 US adults in NHANES 2011-2014 who wore a wrist ActiGraph GT3X+; bright-light exposure was 'time above 1000 lux' (TALT1000, hours/day) and depression was the PHQ-9. In the fully adjusted model (age, sex, race/ethnicity, season, employment, physical activity, sleep duration, BMI, serum cotinine): more time in bright light (>1000 lux) was associated with LOWER depression symptoms (linear beta = -0.19 PHQ-9 points per hour, 95% CI -0.34 to -0.04, P=0.02), consistent in direction with the landmark's day-light/depression association, in a different cohort (different design, exposure and outcome, so not a like-for-like replication). Two nuances temper it: (1) the association was NOT significant for more severe depression (PHQ-9 >=10: OR 0.95, 0.83-1.08, P=0.39); (2) after additionally adjusting for sleep regularity it fell to non-significant (beta = -0.11, -0.26 to 0.04, P=0.13), while more bright light predicted more-regular sleep (beta 1.60, 0.95-2.25) and more-regular sleep predicted lower depression (beta -0.05, -0.06 to -0.03) - so the authors conclude 'greater sleep regularity partly explained the association between greater bright light exposure and lower depression symptoms.' Exploratory vitamin D was linked to light and to sleep regularity but NOT to depression. CROSS-SECTIONAL: the authors say 'causality cannot be ascertained, and associations may be bidirectional' (mood may drive time outdoors). Association, not causation; no medical advice.

Verified research card EL-LM-T03-01-d-R1