People who travel for business at least two weeks a month are more likely to be obese and have poorer self-reported health than people who travel less often. Andrew G Rundle and Catherine A. Richards from Columbia University's Mailman School of Public Health analyzed data from more than 13,000 employees enrolled in a corporate wellness program to study the effect of business travel on health. Results showed that people who traveled at least 20 days each month (extensive travelers) had a higher body-mass index, lower HLD cholesterol, and higher diastolic blood pressure than those who only travelled for 1-6 days each month (light travelers). Extensive travelers were also found to be 260% more likely to rate their health as fair-to-poor compared to light travelers. People who did not travel at all also scored poorly, being 60% more likely than light travelers to rate their health as fair-to-poor. However, the authors note that the poor health observed among non-travelers may reflect a "healthy worker effect," with employees who have health problems being less likely to travel. Richards concluded: “Health outcomes were worse for those not traveling and those traveling the most. While the differences in clinical values for diastolic blood pressure and HDL were small, the results for self-rated health are of concern because this simple measure is a very robust predictor of mortality.”