However, previous studies have shown that the risk of microscopic colitis is definitely highest amongst ladies,1,61,62 making our cohorts ideal populations to study risk factors for microscopic colitis. of microscopic colitis over 6122779 person-years of follow up. Compared to non-smokers, the multivariable-adjusted risk percentage [HR] for microscopic colitis was 2.52 (95% confidence interval [CI] 1.59C4.00) IFNGR1 amongst current smokers and 1.54 [95% CI 1.09C2.17] amongst past smokers. The risk improved with higher pack-years of smoking [pattern = 0.001] and diminished following smoking cessation [pattern = 0.017]. Current smoking appeared to be more strongly associated with risk of collagenous colitis [HR 3.68; 95% CI 1.94C6.97] than lymphocytic colitis [HR 1.71; 95% CI 0.83C3.53]. Summary In two large prospective cohort studies, we observed an association between current smoking and risk of microscopic colitis. Risk of microscopic colitis appeared to increase with higher pack-years and diminish following smoking cessation. Long term studies focused on characterizing the biological mechanisms underlying these associations are warranted. = 0.97].16 Oral contraceptive use was validated by telephone interview of organized life events inside a 1997 study of 215 randomly selected NHSII participants, with 99% agreement between the responses from your interview and the general questionnaires.17 Menopausal status was also validated inside a subset of NHS participants, with reproducibility of menopause status of 98.8% between the 1978 and 1980 questionnaires.18 Race and ethnicity were queried in the 1992 and 2004 questionnaires for NHS and the 1989 and 2005 questionnaires for NHSII. These groups included South Western/Mediterranean ancestry, Scandinavian ancestry, additional Caucasian ancestry, African-American ancestry, Hispanic ancestry, Asian ancestry, Native American ancestry and additional. Starting in 1990 and every 2 years since then, the NHS questionnaire was expanded to include info on use of nonsteroidal anti-inflammatory medicines [NSAIDs].19C21 Similarly, in NHSII, information on regular use of NSAIDs was collected at baseline [1989 questionnaire] and updated biennially through follow up. Consistent with earlier analyses, we defined regular use AM 694 of NSAIDs as intake of two or more tablets per week.19C21 Info on proton pump inhibitors [PPIs], selective serotonin reuptake inhibitors [SSRIs], angiotensin-converting enzyme inhibitors [ACEIs], beta blockers, statins and diuretics has been collected and consistently updated in NHS and NHSII as they became available in the US market. Consistent with their prescription patterns in the US, starting in 2000 in NHS and 2001 in NHSII, info on use of all of these medications was available and updated over follow-up time. 2.4. Ascertainment of instances In both cohorts, a analysis of microscopic colitis was acquired through self-report on the general questionnaire and validated through physician medical record review. In brief, since 1976 in NHS and 1989 in NHSII, participants possess reported diagnoses of IBD, including Crohns disease, ulcerative colitis and microscopic colitis, through open-ended response on biennial studies. In addition, a analysis of IBD has been specifically queried since 1982 in NHS and 1991 in NHSII. When a analysis was reported on any biennial questionnaire, a supplementary questionnaire was sent asking participants specifically for diagnoses of Crohns disease, ulcerative colitis or microscopic colitis. Related medical records were requested and examined by two gastroenterologists blinded to exposure info. We excluded participants who subsequently refused the analysis of microscopic colitis within the supplementary AM 694 questionnaire or declined permission to review their records. Data were extracted on laboratory findings, microbiology studies [e.g. stool studies], endoscopic findings and histopathology. Confirmation of all cases was based on two-physician AM 694 review of histopathology records confirming a pathologist analysis of microscopic colitis. Info on type AM 694 of microscopic colitis, namely lymphocytic colitis and collagenous colitis, were also acquired when AM 694 available. Of 241 reviews of microscopic colitis, we verified 166 [69%] occurrence cases through follow-up after medical record review. Of the, 154 cases got pathology reviews that contained more than enough histological details to discriminate between subtypes of collagenous colitis [= 78] and lymphocytic colitis [= 76]. The rest of the 12 histopathology information stated a medical diagnosis of microscopic colitis without further details. 2.5. Statistical evaluation Participants begun to accrue person-time of follow-up starting at the time of come back of their baseline questionnaire to the time of medical diagnosis of microscopic colitis, loss of life, last came back questionnaire or end of follow-up, whichever.