How common is back pain in women with gastrointestinal problems? 
This study examined the relationship between back pain and gastrointestinal (GI) symptoms in a large scale population study with consideration of possible confounding factors.  Cross-sectional analysis of survey data from the Australian Longitudinal Study on Women's Health was conducted using multinomial logistic regression to model 4 frequencies of back pain in relation to number of GI symptoms (including constipation, hemorrhoids, and other bowel problems).  A total of 38,050 women from 3 age cohorts were included in analysis.  After adjustment for confounding factors, the number of GI symptoms was significantly associated with back pain among all age cohorts.  Odds ratios for experiencing back pain "rarely," "sometimes," and "often" increased with the number of GI symptoms.  Young, mid-age, and older women who experience 2 or 3 GI symptoms had adjusted odds ratios of 3.3 (2.5 to 4.4), 3.0 (2.5 to 3.7) and 2.8 (2.3 to 3.4), respectively, for "often" having back pain.  This study has identified a strong association between back pain and GI symptoms in women.  Possible factors that may account for this relationship include referred pain through viscerosomatic convergence, altered pain perception, increased spinal loading when straining during defecation, or reduced support of the abdominal contents and spine secondary to changes in function of the abdominal muscles.