Inflammatory bowel disease and laterality: is left handedness a risk?

BACKGROUND Left handedness has been associated with inflammatory bowel disease (IBD) and autoimmune diseases. AIMS To determine whether left handedness is associated with IBD in two prospective national birth cohorts. METHODS Subjects with Crohn's disease (CD) and ulcerative colitis (UC) were identified from two national longitudinal birth cohorts at age 26 years (1970 British Cohort Study (BCS70), born in 1970) and age 33 years (National Child Development Study (NCDS), born in 1958). Laterality was determined at age 10 (BCS70) or seven (NCDS) years, based on hand preference for writing and foot preference for kicking a ball (BCS70 only). Multiple logistic regression was used to assess the relationship of handedness with CD, UC, and IBD in the cohorts combined and adjusted for sex. RESULTS Both cohorts combined showed increased adjusted relative odds of 2.13 (95% confidence interval (CI) 0.97--4.65; p=0.059), 2.13 (95% CI 0.92--4.91; p=0. 077), and 2.13 (95% CI 1.20--3.78; p=0.010) for CD, UC, and IBD, respectively in left handers. CONCLUSIONS The study suggests a link between IBD and left handedness which may be genetic and/or environmental in origin.