Prevalence of chlamydia pneumoniae in Japanese rural districts; association of smoking and physical activity with Chlamydia pneumoniae seropositivity.

OBJECTIVE We conducted a large-scale cross-sectional study to assess the prevalence of Chlamydia pneumoniae and clarify the association between seropositivity and risk factors, such as smoking status, physical activity and body mass index in Japanese rural districts. METHODS A total of 1,063 men and 1,573 women aged 18-94 years participated in 1999. Serum index values (ID) of IgA and IgG antibodies to C. pneumoniae were measured by ELISA. Index values were categorized as "negative" (ID < 1.10), "positive" (ID > or = 1.10) and "high positive" (ID > or = 3.00). Logistic regression analysis was performed to estimate the crude and adjusted odds ratios for C. pneumoniae seropositivity. RESULTS The overall prevalence of C. pneumoniae IgA seropositivity was 52.5%, and that of IgG was 55.2%. Each seropositivity significantly increased with age. The prevalence among men was significantly higher than in women in C. pneumoniae IgG "high positive" subjects. Compared with never-smokers, the adjusted odds ratio of current smokers was 2.00 (95% CI: 1.45-2.77) for C. pneumoniae IgA seropositivity. The adjusted odds ratio of the higher tertiles of physical activity for C. pneumoniae IgG seropositivity was 1.42 (1.12-1.80) compared with the lower tertiles. In "high positive" subjects, smoking was associated with both immune complexes. CONCLUSION We confirmed a high prevalence of C. pneumoniae seropositivity among healthy Japanese adults. The results indicated that smoking and high physical activity were associated with C. pneumoniae infection.