Bedtime Delays Alter the Circadian and Seasonal Rhythms of Salivary Amylase Specific Activity in Young Women

This study investigated the effect of bedtime on circadian and seasonal rhythms of salivary amylase specific activity in young females from Raipur, India, under their normal routine life and sleep-wake schedules.Bedtime information was collected from twenty-three females using sleep diaries.Participants were categorized into early (22:30-23:30 hours) and late (23:31-01:30 hours) sleeper groups.Saliva samples were collected at four time points (morning, noon, evening, and bedtime) across four seasons.Salivary amylase specific activity was determined spectrophotometrically by measuring maltose formation using 3,5-dinitrosalicyclic acid (DNS), with protein content estimated by the Lowry method.Rhythm parameters were calculated using cosinor rhythmometry.Two-factor ANOVA revealed a significant effect of season on salivary amylase specific activity in both early and late sleeper groups (p < 0.001), but no significant effect of daily time or season-time interaction.Mean specific activity was significantly higher at noon in early sleepers compared to late sleepers (p < 0.05).Cosinor analysis did not detect statistically significant 24 hours rhythms in either group across seasons.However, significant seasonal variations were observed in 24 hours rhythm parameters: Amplitude was highest during autumn in early sleepers and during winter in late sleepers, while mesor was elevated during autumn and winter in both groups (p < 0.05 for all).Bedtime significantly influences the temporal organization of salivary amylase specific activity, with delayed sleep schedules altering diurnal patterns.Consistent sleep-wake schedules appear important for maintaining normal autonomic and circadian function.