0030 Sleep Regularity Index and Light Regularity Index in Six-month-old Infants

Introduction

There is a bidirectional relationship between sleep patterns and light exposure patterns; in other words, sleep patterns influence light exposure patterns, and vice versa. Sleep regularity can be quantified using the Sleep Regularity Index (SRI), while the Light Regularity Index (LRI) has been recently proposed to measure the regularity of light exposure patterns. A positive correlation between SRI and LRI has been reported in adolescents (Hand et al., 2023). In this study, we tested whether the same correlation exists in six-month-old infants.

Methods

Mothers were recruited from two public hospitals in Ribeirão Preto, São Paulo, Brazil, resulting in a sample of 122 infants (mean age= 6,1 months). The babies wore actigraphs (ActLumus, Condor Instruments) on their ankles for one week. These devices have sensors to detect light exposure. Data were analyzed using pyActigraphy, an open-source Python package for actigraphy, with light exposure specifically processed using the pyLight module. Statistical analysis was conducted in RStudio. For each infant, the mean of the SRI and LRI, as well as the correlation between these variables, were calculated.

Results

As anticipated, a positive correlation of 0.77 (p < 0.001) was observed between SRI and LRI, indicating that higher LRI values were associated with higher SRI values. The means of LRI and SRI were 57.10 and 48.27, respectively.

Conclusion

The correlation between SRI and LRI in infants was significantly stronger than the one reported in adolescents (Hand et al., 2023). We attribute this difference primarily to the autonomy adolescents have in managing their time and schedules, a factor absent in infants. Studying the SRI/LRI relationship across different age groups may provide valuable insights into the synchronization processes of human circadian rhythms.

Support (if any)

FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo); RBMS receives a scholarship from CAPES (Fundação Coordenação de Aperfeiçoamento de Pessoal de Nível Superior).