Effects of Pre-Schooler Lifestyle on the Circadian Rhythm of Secretory Immunoglobulin A

Assuming that secretory immunoglobulin A (s-IgA) in pre-schoolers is influenced by wake-up time, bedtime, sleeping duration and activity, the current study examined the influence of basic pre-schooler lifestyle on the circadian rhythm of s-IgA. We conducted a questionnaire survey on lifestyle and measured steps, heart rate and salivary s-IgA in 44 pre-schoolers aged 4 or 5 years old. Saliva was collected over 2 days at six time points: bedtime, upon waking up, upon arriving at nursery school, before lunch, after lunch and upon going home. To obtain relatively reliable s-IgA values, the s-IgA concentration/total protein concentration ratio (referred to as s-IgA/T.P.) was calculated. Relationship between the s-IgA/T.P. and heart rate, steps, wake-up time, bedtime and sleeping duration was then examined using Pearson’s correlation coefficient. Accordingly, pre-schooler lifestyle had the following effect on circadian rhythm of s-IgA: 1) s-IgA/T.P. values were higher upon waking up than at other measurement time points; 2) pre-schoolers with considerable physical activity had high s-IgA/T.P. at bedtime and upon waking up; and 3) pre-schoolers with long sleeping durations and early bedtime had high s-IgA/T.P. upon waking up. Thus, our results confirmed that pre-schoolers’ lifestyle habits, such as bedtime, sleeping duration, physical activity, had an effect on the circadian rhythm of s-IgA.