Nearly 24,000 Swedish males who had been conscripted into the military between the ages of 16–20 from 1969–1976 received a health check at enlistment, which included measurement of weight, height, and erythrocyte sedimentation rate (ESR). At the time of enlistment, almost 12% of the men were underweight, close to 81% were of normal weight, about 5% were moderately overweight, 1.5% were very overweight, and 1% were obese. The men were monitored for bowel cancer until 2010 using national cancer registry data for an average of 35 years.
During the monitoring period, 885 of the men were diagnosed with bowel cancer, 384 of which were rectal cancers. Men who were very overweight at enlistment were twice as likely to develop bowel cancer compared to those whose weight was within normal range at enlistment, and those classified as obese at enlistment were 2.38 times more likely to develop bowel cancer. In men without known inflammatory bowel disease at the time of their enlistment health check, those with a high ESR of 15+mm/hr had a 63% greater risk of developing bowel cancer than those with a low ESR of <10mm/hr.
Adult obesity and inflammation have been associated with an increased risk of bowel cancer, but these findings suggest that both BMI and inflammation during adolescence may also increase the risk in males as well. Because both factors were independent of one another, weight during adolescence may influence bowel cancer risk via mechanisms other than inflammation, the authors note.
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