Body Mass Index Associated with Risk of Secondary Progressive Multiple Sclerosis

Although high body mass index (BMI) is known to be associated with the development of multiple sclerosis (MS), it is unknown whether BMI also affects the conversion to the progressive form of the disease.

Because most patients with relapsing-remitting MS experience a change to secondary progressive MS (SPMS), increasing the time to development of SPMS, as well as lessening relapse rates, is a treatment goal.

A study published in Frontiers in Neurology aimed to determine whether the risk factors for MS, high BMI, and smoking tobacco extend to the development of SPMS.

The researchers aimed to determine whether patient BMI at age 20, before disease onset, is associated with risk of SPMS. Data were obtained from the Genes and Environment in Multiple Sclerosis study and the Epidemiological Investigation of Multiple Sclerosis study. Questionnaires were collected from patients including information on smoking habits, BMI, and other factors between November 2009 and November 2011.

Overall, 5598 relapsing onset patients diagnosed with MS after the age of 20 from the dataset were included in the study. Patients were divided into 3 groups based on body mass low weight (BMI under 18.5), normal to overweight (BMI of 18.5 to 30), and obese (BMI greater than 30).

The researchers also accounted for smoking status since smoking tobacco has been associated with an increased risk of MS as well. The median pack years smoked before onset for low BMI was 7, compared with 5.50 in the normal BMI group, 5.95 in the overweight group, and 4.93 in the obese group. The proportion of men and women in each smoking category did not significantly vary for each BMI strata.

The findings indicated that patients who were obese at the age of 20 developed SPMS sooner compared with patients in the other 2 groups. Additionally, obesity at age 20 increased the risk of SPMS development in patients who smoked before the onset of disease, which was not seen in non-smokers.

BMI has also been significantly associated with earlier disease onset in other studies.

Overall, BMI has been identified as a factor which not only increases the risk of developing MS, but also of progressing to the SP stage, the researchers concluded. The findings may offer insight to disease-driving mechanisms.

Reference

Manouchehrinia A, Hedstrom AK, Alfredsson L, et al. Association of pre-disease body mass index with multiple sclerosis prognosis. Frontiers in Neurology. 2018. Doi: 10.3389/fneur.2018.00232