Human research · Observational

Windred DP et al., PNAS 2024

Landmark T03 #1, what came after (1): the same team extended the day/night light framework from a cross-sectional mental-health association to a PROSPECTIVE hard outcome - death. Windred et al. 2024 (PNAS; read in full) followed 88,905 UK Biobank adults who wore the same wrist light sensor for one week, for a mean 8.0 years (3,750 all-cause and 798 cardiometabolic deaths). Using Cox proportional-hazards models for all-cause mortality and competing-risks proportional subhazards models for the cause-specific (cardiometabolic) outcomes, adjusting day and night light together (percentile groups 0-50 [ref], 50-70, 70-90, 90-100) plus age, sex, ethnicity, photoperiod and socioeconomic/lifestyle factors (Model 3): the brightest-night group (90-100th percentile) had HIGHER all-cause mortality (adjusted HR 1.21, 95% CI 1.08-1.35, P=0.00064) and higher cardiometabolic mortality (subhazard HR 1.33, 1.06-1.68, P=0.0069), while the brightest-day group had LOWER all-cause mortality (aHR 0.83, 0.72-0.94, P=0.0042); effects were dose-dependent. A computational model of the brain's circadian pacemaker showed that higher modelled circadian amplitude was linked to lower all-cause mortality (mean amplitude aHR 0.96 per SD higher, 0.92-0.99), and early or late circadian phase predicted higher mortality. Adjusting for SHORT sleep attenuated the night-light association (90-100th aHR 1.11, 0.99-1.24, no longer significant), which the authors say indicates short sleep 'partially explains' the night-light association (the 70-90th night group stayed significant: 1.11, 1.02-1.22). This is still OBSERVATIONAL/correlational - the authors state 'since this is a correlational study, it is possible that light exposure patterns and premature mortality are explained by other unmeasured factors'; association, not proof of cause. No medical advice.

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