Adolescent Obesity May Double Later MS Risk

Being obese at 18 years of age can double a woman's later risk for multiple sclerosis, judging from the results of analysis of data from two large, longitudinal cohorts.

The finding that weight during adolescence but not childhood or adulthood is associated with a twofold increased risk for MS further supports a growing body of evidence that the teenage years are an important period in the etiology of the demyelinating disorder, reported Kassandra L. Munger, Sc.D., of the Harvard School of Public Health, Boston, and her colleagues.

The exact mechanism of the association remains to be confirmed, but it might hinge on the low levels of serum 25-hydroxyvitamin D, a marker of vitamin D status, in obese individuals that have been reported by other researchers. Vitamin D is an immunomodulator that has been found to reduce the incidence and progression of MS in animal studies when present in high levels. Current thinking holds that the relatively low levels of the vitamin seen in obese people during adolescence could be an important risk factor, Dr. Munger said.

The data included in the current analysis came from two large studies. One, the Nurses' Health Study (NHS), began in 1976 and involved 121,700 female, married registered nurses who were between 30 and 55 years of age, and living in one of 11 states at the time of enrollment.

The other was the Nurses' Health Study II (NHSII), which involved 116,671 female, married registered nurses who enrolled in 1989 when they were between the ages of 25 and 42 years, and lived in one of 14 states. Participants completed questionnaires on their health behavior and medical information every 2 years.

The researchers identified 241 women diagnosed with MS between 1976 and June 2002 in the NHS cohort. Of these, 166 cases were defined as definite and 75 as probable by the patients' neurologists. Among the NHSII cohort, 352 women were diagnosed with MS between 1989 and June 2003; of these, 278 cases were definite and 74 were probable.

Obesity during adolescence and adulthood was assessed using body mass index (BMI). The baseline questionnaire completed by the participants in either 1976 (NHS) or 1989 (NHSII) included their current weight and height. A later questionnaire completed in 1980 for the NHS cohort and 1989 for the NHSII cohort included data on their weight at age 18. In 1988 (NHS) and 1989 (NHSII), childhood BMI was determined by having women select which of nine silhouettes ranging from very thin to extremely obese best represented their body size at ages 5, 10, and 20 years.

Women with a BMI of 30 kg/m

Women who reported having larger body silhouettes at age 20 also had a twofold greater risk for MS, compared with those who reported a thinner body.

The risk for MS was not affected by obesity in childhood or at the age at the time of enrollment in either study (aged 30-55 years in NHS; aged 25-42 years in NHSII).

Women with MS weighed less than unaffected women. The decrease in relative weight occurred after the diagnosis, a finding that is consistent with findings from previous studies.

Dr. Munger reported receiving honoraria from the Consortium of Multiple Sclerosis Centers and the National Multiple Sclerosis Society. Her associates reported several disclosures.

Being obese at 18 years of age can double a woman's later risk for multiple sclerosis, judging from the results of analysis of data from two large, longitudinal cohorts.

The finding that weight during adolescence but not childhood or adulthood is associated with a twofold increased risk for MS further supports a growing body of evidence that the teenage years are an important period in the etiology of the demyelinating disorder, reported Kassandra L. Munger, Sc.D., of the Harvard School of Public Health, Boston, and her colleagues.

The exact mechanism of the association remains to be confirmed, but it might hinge on the low levels of serum 25-hydroxyvitamin D, a marker of vitamin D status, in obese individuals that have been reported by other researchers. Vitamin D is an immunomodulator that has been found to reduce the incidence and progression of MS in animal studies when present in high levels. Current thinking holds that the relatively low levels of the vitamin seen in obese people during adolescence could be an important risk factor, Dr. Munger said.

The data included in the current analysis came from two large studies. One, the Nurses' Health Study (NHS), began in 1976 and involved 121,700 female, married registered nurses who were between 30 and 55 years of age, and living in one of 11 states at the time of enrollment.

The other was the Nurses' Health Study II (NHSII), which involved 116,671 female, married registered nurses who enrolled in 1989 when they were between the ages of 25 and 42 years, and lived in one of 14 states. Participants completed questionnaires on their health behavior and medical information every 2 years.

The researchers identified 241 women diagnosed with MS between 1976 and June 2002 in the NHS cohort. Of these, 166 cases were defined as definite and 75 as probable by the patients' neurologists. Among the NHSII cohort, 352 women were diagnosed with MS between 1989 and June 2003; of these, 278 cases were definite and 74 were probable.

Obesity during adolescence and adulthood was assessed using body mass index (BMI). The baseline questionnaire completed by the participants in either 1976 (NHS) or 1989 (NHSII) included their current weight and height. A later questionnaire completed in 1980 for the NHS cohort and 1989 for the NHSII cohort included data on their weight at age 18. In 1988 (NHS) and 1989 (NHSII), childhood BMI was determined by having women select which of nine silhouettes ranging from very thin to extremely obese best represented their body size at ages 5, 10, and 20 years.

Women with a BMI of 30 kg/m

Women who reported having larger body silhouettes at age 20 also had a twofold greater risk for MS, compared with those who reported a thinner body.

The risk for MS was not affected by obesity in childhood or at the age at the time of enrollment in either study (aged 30-55 years in NHS; aged 25-42 years in NHSII).

Women with MS weighed less than unaffected women. The decrease in relative weight occurred after the diagnosis, a finding that is consistent with findings from previous studies.

Dr. Munger reported receiving honoraria from the Consortium of Multiple Sclerosis Centers and the National Multiple Sclerosis Society. Her associates reported several disclosures.

Being obese at 18 years of age can double a woman's later risk for multiple sclerosis, judging from the results of analysis of data from two large, longitudinal cohorts.

The finding that weight during adolescence but not childhood or adulthood is associated with a twofold increased risk for MS further supports a growing body of evidence that the teenage years are an important period in the etiology of the demyelinating disorder, reported Kassandra L. Munger, Sc.D., of the Harvard School of Public Health, Boston, and her colleagues.

The exact mechanism of the association remains to be confirmed, but it might hinge on the low levels of serum 25-hydroxyvitamin D, a marker of vitamin D status, in obese individuals that have been reported by other researchers. Vitamin D is an immunomodulator that has been found to reduce the incidence and progression of MS in animal studies when present in high levels. Current thinking holds that the relatively low levels of the vitamin seen in obese people during adolescence could be an important risk factor, Dr. Munger said.

The data included in the current analysis came from two large studies. One, the Nurses' Health Study (NHS), began in 1976 and involved 121,700 female, married registered nurses who were between 30 and 55 years of age, and living in one of 11 states at the time of enrollment.

The other was the Nurses' Health Study II (NHSII), which involved 116,671 female, married registered nurses who enrolled in 1989 when they were between the ages of 25 and 42 years, and lived in one of 14 states. Participants completed questionnaires on their health behavior and medical information every 2 years.

The researchers identified 241 women diagnosed with MS between 1976 and June 2002 in the NHS cohort. Of these, 166 cases were defined as definite and 75 as probable by the patients' neurologists. Among the NHSII cohort, 352 women were diagnosed with MS between 1989 and June 2003; of these, 278 cases were definite and 74 were probable.

Obesity during adolescence and adulthood was assessed using body mass index (BMI). The baseline questionnaire completed by the participants in either 1976 (NHS) or 1989 (NHSII) included their current weight and height. A later questionnaire completed in 1980 for the NHS cohort and 1989 for the NHSII cohort included data on their weight at age 18. In 1988 (NHS) and 1989 (NHSII), childhood BMI was determined by having women select which of nine silhouettes ranging from very thin to extremely obese best represented their body size at ages 5, 10, and 20 years.

Women with a BMI of 30 kg/m

Women who reported having larger body silhouettes at age 20 also had a twofold greater risk for MS, compared with those who reported a thinner body.

The risk for MS was not affected by obesity in childhood or at the age at the time of enrollment in either study (aged 30-55 years in NHS; aged 25-42 years in NHSII).

Women with MS weighed less than unaffected women. The decrease in relative weight occurred after the diagnosis, a finding that is consistent with findings from previous studies.

Dr. Munger reported receiving honoraria from the Consortium of Multiple Sclerosis Centers and the National Multiple Sclerosis Society. Her associates reported several disclosures.