Abstract
Although seasonal variation in high-sensitivity C-reactive protein (hsCRP) has been studied cross-sectionally and longitudinally, the results to date have been mixed. Here, to test seasonal variation in this compound with regard to within-subject, inter-day variation, we conducted a longitudinal follow-up study with repeated measurements in Japanese workers with low hsCRP. Blood samples were obtained from four male indoor daytime workers, who were aged 32–57 and commuted to offices in Kawasaki City, on six days within 2-wk windows in February and October, 2008. Serum hsCRP was measured using ultrasensitive latex-enhanced immunonephelometry. Among the subjects with detectable levels of hsCRP, individual median serum hsCRP levels were 38–74% higher in October than in February (p=0.03). This study identified the presence of a seasonal variation in the serum hsCRP level of Japanese workers with low hsCRP levels.
