Quantitative Study of Indoor Light and Sleep Health in Elderly

Abstract

Objective

Current lighting recommendations rely on Western laboratory studies, leaving the real-world mechanisms linking light exposure to sleep in Asian older adults unclear. This study aims to systematically analyze the complex relationships among daily light exposure, activity patterns, and sleep health in older adults living in residential environments.

Background

Existing lighting guidance for sleep and circadian health is predominantly based on Western laboratory research, with no clear elucidation of the real-world associative mechanisms between light exposure and sleep among Asian older adults. This study targets this research gap by exploring the relevant correlations in real residential settings, to lay a foundation for targeted lighting improvement for the elderly population.

Methods

We employed a field investigation combining subjective and objective measurements in the living spaces of 116 elderly participants in Shanghai, China. Individual ocular light exposure and activity patterns were collected via luxmeters and interviews. Sleep quality and chronotype were assessed using the Pittsburgh Sleep Quality Index (PSQI) and Munich Chronotype Questionnaire (MCTQ). Hierarchical multiple linear regression was employed to examine associations, controlling for age and gender.

Results

Field measurements confirmed that participants' indoor environments were pervasively light-deficient, lacking sufficient daytime stimulus for robust circadian entrainment. Age was the strongest negative predictor of sleep efficiency (β= -0.419, p < 0.001). After controlling for age, the light environment explained a significant 9.3% of additional variance (p = 0.012). Notably, higher maximum daytime ocular illuminance (Ev) was associated with lower sleep efficiency (β = -0.413, p = 0.015), while higher maximum evening ocular illuminance (Ev) was associated with higher sleep efficiency (β = 0.279, p = 0.008).

Conclusions

These findings challenge simplistic guidelines: high daytime light peaks likely represent uncomfortable glare rather than effective circadian stimulus, while evening light proxies for beneficial social activity. This underscores the urgent need for context-aware, glare-free residential lighting strategies to promote healthy aging among older adults.