Researchers from the Yale School of Public Health in New Haven, Connecticut have reported findings that implicate obesity and smoking as significant risk factors for myelodysplastic syndromes (MDS). This is the first study ever to evaluate lifestyle factors as possible causes of MDS.

Researchers collaborated with the National Institutes of Health American Association of Retired Persons (AARP) Diet and Health Study, an organization that involves more than 560,000 men and women across the United States. Members between 50 and 71 years of age residing in six states (California, Florida, Louisiana, New Jersey, North Carolina, and Pennsylvania) and two metropolitan areas (Atlanta and Detroit) were mailed questionnaires asking about demographics, dietary intake, and health-related behavior. The study tracked participants from 1995 or 1996 until either their date of death, diagnosis of MDS, relocation out of the registry area, or December 31, 2003 – whichever was earliest.

A total of 471,799 AARP members participated in the study. Researchers examined self-reported weight, height, smoking, physical activity, alcohol consumption, and diet, as well as demographic variables such as age, sex, race or ethnicity, and education. They analyzed these factors as potential variables and causes of MDS.

Results showed obese participants (body mass index (BMI) >30) were more than twice as likely to develop MDS as overweight (BMI 25 to <30) or normal weight (BMI 18.5 to <25) participants. Among participants, 35 percent were of normal weight, 43 percent were overweight, and 22 percent were obese. In addition, participants who reported being physically active a minimum of 20 minutes three times a week reduced their risk of MDS by 32 percent, compared to people who were active less than three times a month.

Researchers recommend more studies be conducted to specify the mechanism through which obesity may cause MDS. One potential pathway involves insulin resistance as a result of obesity. Insulin may promote excess division of blood cells and eventually lead to MDS. Leptin, which normally suppresses appetite, increases the rate of metabolism, and plays a role in the division of blood cells, also possibly links obesity and MDS. Blood precursor cells may develop abnormally over time if the body absorbs irregular levels of leptin.

In addition, both former and current cigarette smokers had higher risks of MDS compared to participants who had never smoked. Current smokers who smoke more than one pack a day increase their risk by more than four-fold. This is because cigarettes are a common source of exposure to benzene, a hydrocarbon which can cause secondary MDS.

Results showed that alcohol consumption, fruit and vegetable intake, and total meat intake were not associated with MDS.

An overall analysis showed MDS highly correlated with obesity, regardless of gender, smoking, and physical activity. Obese participants were more likely to be male, less educated, physically inactive, non- smokers, and have high energy and meat intakes with lower alcohol consumption.

More studies are needed to determine the risks of obesity and smoking to MDS in people under 50 years.

For more information, please see the study in the American Journal of Epidemiology (abstract).