Anecdotal evidence has long described a positive association between being lean or underweight and developing amyotrophic lateral sclerosis (ALS). Now, results from a large-scale study conducted in Europe appear to confirm these observations, showing that individuals with more body fat have a decreased risk of developing the disease.
The identification of such a nongenetic risk factor could help scientists better understand and determine the causes of ALS.
Investigators studied more than half-a-million people recruited from the general population across 10 Western European countries for a study called European Prospective Investigation into Cancer and Nutrition, or EPIC. (In a “prospective” study, data is collected before a disease manifests.)
At recruitment, participants provided information on lifestyle and dietary habits. Weight and height measurements were used to calculate each participant's body mass index, or BMI, and assign one of four standard BMI classifications: underweight, normal weight, overweight or obese. Waist and hip circumference measurements also were recorded.
(BMI is a measure of body "fatness" and can be calculated by multiplying one's weight in pounds times 4.88 and dividing the result by one's height in feet squared. The body mass index calculator provided by the National Institutes of Health will do the math for you. )
Within the 518,108-person group, a total of 222 deaths (79 men and 143 women) were attributed to ALS during a 13-year follow-up period.
Analysis showed a statistically significant association between body mass index and gender, and ALS risk. Overall, underweight individuals had a significantly increased risk of ALS.
Height was not associated with ALS.
The investigators noted that factors that potentially could have influenced the results included participants' age at recruitment, education levels and smoking histories. They noted that inclusion of smoking and education information did not significantly change the ALS risk estimates, however.
The international research team reported its findings online Feb. 6, 2013, in Neurology. To read the full report (there is a $30 charge), see Prediagnostic Body Fat and Risk of Death from Amyotrophic Lateral Sclerosis.
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