As the average age of people with multiple sclerosis (MS) increases, it becomes even more critical to accurately measure the degree of disability among those with MS, explains Sharon Lynch, MD. “Expanded Disability Status Scale (EDSS) score changes are assumed to be due to worsening MS-related disability,” she says. “However, strict interpretation of measurements may register some normal findings as abnormal, inflating the disability score. Furthermore, determining the cause of neurologic symptoms can be difficult in an older population with comorbid illness and polypharmacy. If the measurement is inaccurate, our understanding of the consequences of the disease, and the results from our clinical trials, could be incorrect.”
For a paper published in Multiple Sclerosis and Related Disorders, Dr. Lynch and colleagues aimed to examine the association between EDSS score, age, comorbidities, and polypharmacy. The study team conducted a pilot project to evaluate 106 individuals older than 55, with and without MS. “We collected information on comorbid conditions and the effects of polypharmacy that might influence test results,” Dr. Lynch explains. “We chose a ‘friends and family’ approach to recruiting people without MS, asking the friends and family of people with MS to participate in order to include individuals of a similar socioeconomic background. All participants came to our center and answered questionnaires about their health, medications, and underwent an EDSS assessment by a neurologist who was unaware of their diagnosis.”
No EDSS Scores of 0
The assumption of the EDSS is that all abnormalities measured are the result of the disease process, Dr. Lynch notes. “However, neurological examinations change with age, while the requirements of the scale do not,” she says. “If our measurements do not take this into account, they will falsely overestimate the effect of MS on their disability scale. For instance, the cerebellar scale requires a normal tandem gait for a score of 0. Many people older than 65 cannot perform a tandem gait, even without any established neurological disability.” The study team set out to determine if the EDSS score of a person without MS would truly be 0, or if not, what factors would affect this outcome. “The most important finding of our study was that in our sample, no one, even those without MS, had an EDSS score of 0,” Dr. Lynch notes. “In addition, in our subjects without MS, the EDSS score increased with age. This suggests that at least some of the measures of disability we report in our older population of patients with MS could be caused by age alone, and not by the disease process.”
Not All Health Problems Caused by MS
Dr. Lynch and colleagues also examined which comorbidities were common in the MS population and compared those with the non-MS population. “Our study illustrates the percent of reported comorbidities for both groups,” she says. “No significant between-group differences emerged for the number of comorbidities. Misidentification occurred equally across participants, with and without an MS diagnosis (Figure).”
These findings indicate that the EDSS scoring should be reassessed in the aging population to allow for a more nearly accurate assessment of disease-related disability in the MS population, according to Dr. Lynch. “We also need to be aware that not all health problems in a patient with MS are caused by MS, and we should evaluate them for other conditions that might contribute to their disability,” she says.
Dr. Lynch and colleagues suggest the need for larger studies to reassess the measurement of the EDSS in older populations. “Some of the functional status system details could be reevaluated to account for aging,” she says. “The measurement should also take polypharmacy and comorbidities into account.”