Obesity linked to faster optic nerve degeneration

Being obese is linked to a faster degeneration of optic nerve tissue in people with multiple sclerosis (MS) than in those of a normal body weight, a new study has found.

Researchers at Johns Hopkins University, who conducted the study, say that because optic neuropathy indicates greater brain nerve cell loss, tracking retinal changes could help them understand if lifestyle choices and behaviour can improve MS development.

Degeneration in part of the back of the eye called the ganglion cell and inner plexiform layer (GCIPL) has a correlation with worse disability, disease activity and brain atrophy. The researchers investigated whether obesity in people with MS increased damage in this area of the eye.

There were 513 participants in the study. By measuring their body-mass index (BMI), they were classified as either being of normal weight (214 people), overweight (153 people), or obese (146 people).

Except for their BMIs, the participants were matched fairly similarly in terms of age, disease subtype and duration.

Researchers assessed damage to the optic nerve using a method called optical coherence tomography (OCT), which acquires cross-section images of the retina using light waves. This allows them to measure the thickness of layers in the eye. In the first assessment, participants of normal weight tended to have lower GCIPL thickness than the overweight and obese, because they had had more severe optic neuritis.

Participants then had a follow-up a (mean) average of 4.4 years later. Researchers found that obese participants had a much faster atrophy in the GCIPL layer than the people who were of normal weight. The obese people’s rate of GCIPL thickness reduction each year was 0.57%, compared with 0.42% in the normal weight group. Comparison between the overweight and normal weight group was not statistically significant, though.

In addition to body weight, factors like being African-American, male, and having progressive MS were all also found to be independently associated with a faster GCIPL degeneration.

The researchers say that these findings support previous research which has suggested having an elevated BMI is linked with more rapid disease progression. A study last June found that elevated leptin – a hormone produced by fats cells – might contribute to neuroinflammation and increased severity of MS. Obesity in childhood and adolescence is also known to be a risk factor for MS.

These findings suggest that diet and lifestyle changes to reduce body fat could improve the outcomes for people living with MS.