Amyotrophic lateral sclerosis (ALS) prevalence in a large group of patients with Medicare coverage was found to be higher than that previously reported in the U.S., according to a study.
Findings also revealed that having ALS was associated with shorter survival than other motor neuron diseases (MND).
The study, “Amyotrophic lateral sclerosis among patients with a Medicare Advantage prescription drug plan; prevalence, survival and patient characteristics,” appeared in the journal Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration.
Data on the incidence, prevalence, and survival of ALS vary by geography and study design. In the U.S., a 2014 report from the National ALS Registry indicated a prevalence of five cases per 100,000 people, in line with global results. Other studies identified older age, lifestyle choices such as smoking, and genetics as potential risk factors for this disease.
In this study, researchers used a validated algorithm to better understand ALS prevalence, patient characteristics, five-year survival, and factors associated with mortality in adults ages 18-90 with Medicare Advantage prescription drug (MAPD) coverage from a single organization.
The analysis used health plan enrollment information, as well as medical, pharmacy, and laboratory claims data between 2007 and 2011.
Of a total of 2,631 individuals with an MND diagnosis, 1,271 (48%) had ALS, 1,157 (44%) were in the “no ALS” category, and 203 (8%) were classified as “possible ALS.”
ALS prevalence was 20.5 per 100,000 over the five-year period and 11.8 per 100,000 in 2011. This is higher than the rate in the 2014 report, the investigators noted, adding that it likely results from the higher proportion of older adults in their study. Another potential explanation is the lack of data on specific cause of death, unlike in the 2014 National ALS Registry findings.
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The prevalence decreased in patients ages 50-59 (11.7 per 100,00 in 2011) and continued to lower in those ages 60-69 (7.9 per 100,000 ), but increased in older patients — 14.3 in ages 70-79 and 18.3 in ages 80-89 per 100,000.
Both the five-year and 2011 prevalence were higher for men — 26.2 and 16.1 per 100,000, respectively, compared with women (15.8 and 10.6 per 100,000, respectively).
The 2,121 patients with 60 days of continuous health plan coverage before index — which refers to the first claim with a diagnosis of motor neuron disease or ALS — were followed through Dec. 31, 2016. Among this group, 958 patients (45%) were classified as ALS, 978 (46%) as no ALS, and 185 (9%) as possible ALS. This subgroup of possible ALS was older than the no ALS category (mean age of 73 vs. 69 years), and had higher proportion of men (63.8% vs. 51.3%) and dual-eligibility for Medicare and Medicaid.
The patients with no ALS before the first medical claim had a greater proportion of diseases of the circulatory, genitourinary, musculoskeletal, and endocrine systems, as well as of cancer, injury, poisoning, and mental illness than the other two groups. This suggests that disease processes in ALS may differ from other MNDs, “presenting significant challenges in differential diagnosis,” according to the researchers.
Having a disorder other than ALS was also associated with more frequent emergency department visits and hospitalizations, while physician office, outpatient visits, and annual use of testing services were more common for those classified as ALS.
Results also showed that ALS patients had the lowest survival rate (19%) through the end of follow-up, compared with 65% in people with no ALS and 98% in those with possible ALS. The median survival time was 388 days for the ALS group, 542 days for the no ALS group, and 1,473 days for the possible ALS group.
After accounting for patients’ baseline characteristics, the team then found that having a classification of ALS was associated with a 2.85 times higher mortality risk compared with the no ALS group.
Other factors also associated with shorter survival included having respiratory and genitourinary diseases, older age, the number of pre-index acute inpatient admissions, and seeing a psychiatrist or neurologist at the index visit.
No patient with possible ALS was classified as ALS during five more years of follow-up.
“Surveillance data from a Medicare population demonstrated a higher prevalence of ALS,” the scientists wrote. “[The] results highlight the need for effective ALS treatment options and resources for patients with ALS.”
Of note, three of the study’s authors are employed by Humana, a health insurance provider for ALS patients.