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Abstract Introduction Sleep disturbance and circadian rhythm disruptions are common among adults with chronic heart failure (HF), and are related to cognitive impairment. Although light levels are known to influence sleep quality, cognition, and the circadian system, little is known about the role of light among adults with HF. The purpose of this study is to investigate the association between light exposure and sleep, diurnal rest-activity rhythms (RAR), and cognitive function among adults with HF. Methods We retrospectively analyzed baseline data from a randomized controlled trial of cognitive behavioral therapy for insomnia for adults with HF and insomnia. We measured light levels and sleep with 24-hour wrist actigraphy and computed the circadian quotient, inter-daily stability, and intra-daily variability (strength of the RAR) using cosinor and non-parametric methods. We computed time above threshold (TAT) (100, 500, and 1000 lux), ratio of light exposure in daytime to evening (AUC ratio), and light regularity index (LRI) (20, 50, and 100 lux) to assess the intensity and consistency of light exposure patterns. Lapses in performance on the Psychomotor Vigilance Task (PVT lapse) measured cognitive function. Multiple linear regressions tested if the light exposure metrics could predict the RAR, sleep efficiency, and PVT lapses after adjusting for age, sex, and comorbidities. Results The sample included 167 participants (M age=63.8 (SD =12.9) years; 45.5%female). The AUC ratio and TAT500 were associated with a stronger circadian quotient in males (0.339 ± 0.095, p=.0005; 0.296 ± 0.085, p=.0006) compared to females (0.058 ± 0.106, p=.5800; -0.061 ± 0.128, p=.6364), after controlling for age and comorbidities. TAT500 was associated with better inter-daily stability (0.221 ± 0.077, p=.0044) than the other thresholds. Higher light exposure intensity (TAT100) (0.129 ± 0.065, p=.0492) and a greater circadian quotient (0.267±0.076, p=.0006) were associated with improved sleep efficiency. TAT100 was associated with fewer PVT lapses (-0.229 ± 0.082, p=.0061), after controlling for total sleep time, circadian quotient, and demographics. Conclusion Light exposure, particularly at certain intensities and regularity, predicted RARs, sleep efficiency, and cognitive function in adults with HF. Future tailored light interventions with varying intensities and regularity may improve HF outcomes. Support (if any)
Wang et al. (Sat,) studied this question.