Rurality Modifies the Association Between Symptoms and the Diagnosis of Amyotrophic Lateral Sclerosis
Abstract
Objective: We utilized national claims-based data to identify the change in hazard of diagnosis of ALS following a possible ALS-related diagnosis (e.g., falls) and whether the change in hazard varies whether the patient lives in an urban or rural area. Methods: Health insurance claims data from both the commercial insurance market and Medicare supplemental market were obtained from the Merative MarketScan Commercial Claims and Encounters and Medicare Coordination of Benefits databases. Individuals with a diagnosis of ALS were identified and matched on age, sex, and enrollment period to individuals without ALS. For all individuals, inciting events such as falls, muscle related symptoms, or bulbar symptoms were also extracted. We then used fixed-effects regression to estimate the risk of being diagnosed with ALS following one of these events controlling for urban-rural status. Additionally, we utilized interaction terms to evaluate the effect of rurality on odds of diagnosis. Results: 19,126 individuals with ALS were included with 96,126 controls. Patients with ALS were more likely than matched controls to live in an urban area (87 vs 85%). Of those with ALS 84% had a symptom code preceding their diagnosis as compared to 51% in the general population. The association between having any symptoms and future diagnosis of ALS remained statistically significant after adjustment for confounders and an odds ratio of nearly 5. Odds ratios for the individual symptoms varied from 1.2 to over 10. In all models, living in an urban area was associated with increased odds of diagnosis with ALS while the effect of having a symptom was smaller among urban dwellers. Urban dwellers who are diagnosed with ALS are diagnosed at younger ages. Conclusions: Early diagnosis of ALS is vital for connecting patients with research and treatment options. These results suggest symptoms appear in the administrative health record potentially years before the diagnosis of ALS. Additionally, rural patients are diagnosed at later ages with a greater dependence on major symptoms than urban patients. These results highlight potential improvements for surveillance and screening for ALS.
