Effects of light therapy on sleep efficiency in older adults in long-term care facilities: a systematic review and meta-analysis

Purpose: This study aimed to systematically review the effects of light therapy on sleep efficiency in institutionalized older adults and to analyze effect sizes according to the characteristics of light therapy.Methods: A comprehensive literature search was conducted using RISS, KMBASE, KISS, NDSL, KISTI, NAL, PubMed, EMBASE, Cochrane Library, CINAHL, and ProQuest Global. Manual searches of reference lists were also performed. A total of 1,597 records were identified, and nine studies met the inclusion criteria and were included in the final analysis. Following quality assessment, all eligible studies were analyzed using RevMan and R software.Results: The overall effect size of light therapy on sleep efficiency was 0.67 (95% confidence interval [CI ]: 0.13~1.21), indicating a beneficial effect. In subgroup analyses, studies using light intensity ≥ 5,000 lux showed a significant effect size of 1.58 (95% CI: 0.80~2.37). For studies with light exposure durations shorter than 1 hour (n = 4), the effect size was 1.40 (95% CI: 0.74~2.06). Similarly, studies with intervention periods shorter than 3 weeks (n = 4) demonstrated an effect size of 1.40 (95% CI: 0.74~2.06). However, heterogeneity was high in all analyses. In contrast, when light application timing was categorized as morning, afternoon, or all day, no significant effects were observed.Conclusion: Despite considerable heterogeneity, light therapy showed beneficial effects on sleep efficiency in institutionalized older adults. When applying light therapy, factors such as appropriate light intensity, exposure duration, and intervention period should be carefully considered.