Risk of colorectal cancer in women with pelvic inflammatory disease: A matched cohort study

Objective: Inflammation is an important risk factor for the development of colorectal cancer (CRC). Pelvic inflammatory disease (PID) comprises a spectrum of upper genital tract infections and inflammatory diseases. We aimed to evaluate the association between CRC and PID. Design: Matched cohort study using the National Health Insurance Research Database. Setting: Women with PID in Taiwan. Population and sample: From the Longitudinal Health Insurance Database 2005 (LHID2005) in Taiwan, we obtained data on women from 13 to 45 years of age who were diagnosed with PID. The women with PID were matched 1:4 to selected members of the population without PID based on age and year of first entry into the LHID2005. Methods: A Cox proportional hazards model was used to evaluate the hazard ratio for CRC during the 5-year follow-up period, after adjusting for sociodemographic characteristics and selected comorbid medical disorders. Main outcome measures: Colorectal cancer. Results: Of the 19 029 women with PID, 30 were diagnosed with CRC during the 78 965 person-year follow-up period. Of the 76 116 control women, 66 were diagnosed with CRC. The CRC hazard ratio during the 5-year follow-up period was 2.00 (95% CI 1.30-3.08) for women with PID relative to control women. Similarly, after adjusting for age, Charlson comorbidity index score, urbanisation level and monthly income, the adjusted CRC hazard ratio was 1.71 (95% CI 1.10-2.65) for the women with PID relative to the women in the comparison cohort. Conclusions: Here we show a weak association between PID and CRC. Additional studies are needed to further evaluate this association and examine plausible mechanisms, including the influence of specific microorganisms.