Familial aggregation of irritable bowel syndrome: a family case-control study.
OBJECTIVE
Irritable bowel syndrome (IBS) clusters in families, but previous studies documented family history only from patients. We have shown that patient-relative agreement on IBS status is poor. Thus, we conducted a family case-control study with direct survey of symptoms from family members to better quantitate the aggregation of IBS in families. The aims of this study were to (i) compare the prevalence of IBS in case-relatives with control-relatives, and (ii) determine whether gender, relationship, predominant symptom, and environmental risk factors affect familial aggregation.


METHODS
Outpatients with IBS, matched controls, and their first-degree relatives completed a bowel symptom questionnaire. Percent of cases and controls with a family history were compared and odds ratios were computed using chi(2)-test; recurrence risks to relatives were computed using logistic regression and generalized estimating equations.


RESULTS
Data were collected from 477 cases, 297 controls, 1,492 case-relatives, and 936 control-relatives. Probands had a median age of 50 and 78% were women. 50% of case and 27% of control families had at least another relative with IBS yielding an odds ratio of 2.75 (95% CI: 2.01-3.76, P<0.0001). When aggregation estimates were reevaluated stratifying by relative relationship or proband gender, generational and gender effects were not observed. Familial clustering by bowel habit was weakest for diarrhea, and strongest for alternating bowel habits.


CONCLUSIONS
IBS aggregates strongly in families. The strength of the association does vary somewhat by relationship to proband, but the lack of association in spouses supports either a possible genetic etiology or a shared household environmental exposure as an underlying cause of IBS.
Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota, USA. saito.yuri@mayo.edu
Yuri A
YA
Saito
Gloria M
GM
Petersen
Joseph J
JJ
Larson
Elizabeth J
EJ
Atkinson
Brooke L
BL
Fridley
Mariza
M
de Andrade
G Richard
GR
Locke
Janice M
JM
Zimmerman
Ann E
AE
Almazar-Elder
Nicholas J
NJ
Talley
D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000235:genetics*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011788:Quality of Life; D012008:Recurrence; D012307:Risk Factors; D011795:Surveys and Questionnaires