The rate of weight loss from onset to diagnosis can be a significant indicator of poorer outcomes among amyotrophic lateral sclerosis (ALS) patients, a study reports.
The study, “Early weight loss in amyotrophic lateral sclerosis: outcome relevance and clinical correlates in a population-based cohort,” was published in the Journal of Neurology, Neurosurgery and Psychiatry.
The underlying causes of ALS, a degenerative neurological disease affecting motor nerve cells, are still not fully understood, as genetic errors or mutations account for only about 10 percent of all cases.
Recently, scientists have been exploring weight loss, nutritional status, and bulbar involvement (the brain area that controls the muscles, face, and neck) as possible prognostic factors. A previous study reported that body mass index (BMI), a measure of body fat based on height and weight, was a strong predictor of ALS prognosis, but follow-up studies have produced conflicting results. (Bulbar-onset ALS patients are known to have dysphagia, or difficulties swallowing.)
In this study,
the researchers in Italy took a fresh look at the value of BMI and the weight loss rates as prognostic factors in ALS.
They enrolled 620 patients (342 men and 278 women) — average age of 66 — who were diagnosed with ALS between January 2007 and December 31, 2011.
To assess BMI and weight loss, researchers obtained the body weight at diagnosis (DBW) and defined the patients’ body weight three years before ALS diagnosis as the health body weight (HBW). Patients and their caregivers were then asked about changes in their weight three years before the start of motor symptoms. These parameters were used to calculate the monthly weight loss percentage.
By comparing HBW with DBW, the authors found that the DBW decreased in 383 patients, was unchanged for 179, and increased for only 58 patients.
While this diagnostic body weight was not linked to prognosis, patient outcomes were significantly associated with the monthly mean percentage of weight loss. Compared to those with a weight increase at diagnosis, patients who lost 1 percent or more of their weight each month had half as long a median survival.
Patients were then divided into four groups: bulbar onset (group 1), spinal onset, with dysphagia at diagnosis (group 2); spinal onset without dysphagia, with an average weight loss of 1 percent or more each month (group 3); and spinal onset without dysphagia, with an average weight loss of less than 1 percent (group 4).
Average survival of those in the first three groups was similar (1.8 to 2.0 years), but the fourth group had a longer median survival of 3.5 years.
In group 2, 19% of the patients had an average monthly percentage weight loss equal to or higher than 1 percent and their median survival of 1.8 years was very similar to that of bulbar-onset patients, who are known to have the worst prognosis.
Researchers observed that the relevance of early weight loss in ALS is corroborated by the physiological mechanism behind it. While bulbar disturbances make eating difficult for those with this disease type, about half of all ALS patients are reported to have an increased metabolic rate, expending more energy because of underlying respiratory problems.
A subgroup of patients with spinal onset without dysphagia at diagnosis, but difficulties with breathing, showed a rapid and severe weight loss before diagnosis. The study noted the importance of an earlier treatment for respiratory dysfunction in these people.
In future clinical trials, they added, a reliable stratification could make a difference in the clinical management and outcome of ALS patients, and early weight loss could be helpful in a more accurate prognosis.
“This finding indicates the importance of evaluating early weight changes in purely spinal patients, in order to identify and promptly treat the potential underlying respiratory impairment,” the study concluded.