Daytime variations of interleukin-1beta in gingival crevicular fluid

Interleukin-1beta (IL-1beta) is an important parameter in periodontal research because of its role in inflammation and bone resorption. One measure used to assess local IL-1beta concentrations is analysis of its levels in gingival crevicular fluid (GCF). While studies on serum IL-1beta concentrations indicate a circadian rhythm of this parameter, nothing is known about daytime variations of IL-1beta in GCF. The present study thus aimed to analyse such variations. Daytime variations of GCF-IL-1beta between 08:00 and 22:00 h were assessed, with a time resolution of 2 h, in 28 periodontally healthy subjects. The data showed a significant variation throughout the day, with the lowest concentrations and total amounts in the morning and the highest in the evening. The effect sizes of comparisons between morning and evening samples were medium to high and corresponded in magnitude to those reported in other published research comparing healthy sites and those affected by periodontitis. The smallest daytime variations were found to occur between 12:00 h and 18:00 h. It is concluded that daytime variations in GCF-IL-1beta are large enough to be able to mimic or mask differences caused by clinical factors.