Variation of salivary flow rate in adolescents.

Forty-three children living in North Wales, an area with a temperate climate, were involved in this study from September 1990 until June 1991 inclusive. By standardizing the method and timing of collection the effect of external factors on the salivary flow rate was minimized. Flow rate was assessed once a month. Of the original group of 43, 18 attended at each occasion; these were termed the "regular attendees". Repeated-measures analysis of variance indicated that unstimulated salivary flow rate varied within an individual over time in both the total (43, p < 0.001) and the regular groups (18, p < 0.001). This relation remained when the initial September and October measurements were excluded (p < 0.05, n = 43). When the subgroup, the regular attendees (n = 18), was considered, this relation almost reached statistical significance when September was excluded (p = 0.052) and when both months were omitted the association was no longer evident (p = 0.094). Similar to previously published results from a study of individuals in a subtropical climate, salivary flow-rate variation was inversely associated with ambient temperature in both the total (n = 43) and the subsection of regular attendees (n = 18) (p < 0.05).