Giardiasis and Subsequent Irritable Bowel Syndrome: A Longitudinal Cohort Study Using Health Insurance Data.
Giardia intestinalis is the most commonly reported human intestinal parasite in the United States. Increased incidence of chronic gastrointestinal complaints has been reported after some giardiasis outbreaks. We examined the relationship between giardiasis diagnosis and irritable bowel syndrome (IBS) diagnosis.



We used the 2006-2010 MarketScan commercial insurance database. Persons with at least 1 giardiasis diagnosis were individually matched on age group, sex, and enrollment length in months to 5 persons without a giardiasis diagnosis. Persons diagnosed with IBS before the date of study entry were excluded. We calculated crude incidence rates (IRs) and developed Cox proportional hazards models.



The matched cohort included 3935 persons with giardiasis and 19663 persons without giardiasis. One-year incidence of IBS was higher in persons with giardiasis (IR = 37.7/1000 person-years vs 4.4/1000 person-years). The unadjusted hazard ratio was 4.8 (95% confidence interval [CI] = 3.6-6.4), attenuated slightly to 3.9 (95% CI = 2.9-5.4) after adjusting for anxiety, depression, and healthcare utilization.



In a large insurance database, individuals diagnosed with giardiasis were more likely to have a subsequent IBS diagnosis, despite accounting for confounders. Future research on risk factors for IBS among giardiasis patients and the pathophysiology of postinfectious IBS is needed.
Epidemic Intelligence Service, Epidemiology Workforce Branch, Division of Scientific Education And Professional Development, Center For Surveillance, Epidemiology And Laboratory Services, Office of Public Health Scientific Services, Centers for Disease Control and Prevention, Atlanta, GA, USA.|Waterborne Disease Prevention Branch, Division of Foodborne, Waterborne and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
Jolene H
JH
Nakao
Waterborne Disease Prevention Branch, Division of Foodborne, Waterborne and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
Sarah A
SA
Collier
Waterborne Disease Prevention Branch, Division of Foodborne, Waterborne and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
Julia W
JW
Gargano
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D016208:Databases, Factual; D004196:Disease Outbreaks; D005260:Female; D005873:Giardiasis / Q000150:complications* / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007223:Infant; D043183:Irritable Bowel Syndrome / Q000453:epidemiology / Q000209:etiology*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012307:Risk Factors; D055815:Young Adult
claims data; gastroenteritis; post-infectious irritable bowel syndrome; billing data