Seasonal variation of C-reactive protein in apparently healthy Koreans.

BACKGROUND: C-reactive protein (CRP) is known as an emerging recognized marker of the potential risk of myocardial infarction and stroke, and several studies have reported higher incidences of cardiovascular events during the winter months. Here, we investigated seasonal CRP variations using a high-sensitivity immunoradiometric assay in apparently healthy Koreans.
METHODS: This study included 18,445 apparently healthy Koreans (12,064 men and 6381 women, 47.2 (11.5) years of age). Anthropometric indices of adiposity, metabolic variables, blood pressure (BP), and several cardiovascular risk factors were measured. High sensitivity CRP testing was performed by immunonephelometry.
RESULTS: The mean (SD) CRP level in the study population was 1.66 (2.15) mg/L, and mean (SD) CRP levels in the spring, summer, fall and winter were 1.76 (2.30) mg/L, 1.51 (1.94) mg/L, 1.61 (2.08) mg/L, and 1.76 (2.30) mg/L, respectively. After adjusting for age, sex, diabetes, hypertension, regular exercise, smoking, and body mass index, the odds ratios of an elevated CRP in the spring, fall and winter season were 1.196 (95% CI, 1.024-1.396 p = 0.024), 1.086 (95% CI, 0.943-1.250 p = 0.251) and 1.258 (95% CI, 1.088-1.456 p = 0.002), respectively, as compared with the summer season.
CONCLUSIONS: Our results indicate a highly significant seasonal variation in CRP levels, with higher values during winter and spring than in summer. Elevated plasma CRP levels can be related to an increased risk of cardiovascular events, which are more prominent during the winter months. To further elucidate this relationship additional studies are needed.