The Incidence of Amyotrophic Lateral Sclerosis in Ohio 2016-2018: The Ohio Population-Based ALS Registry

Estimated Familial Amyotrophic Lateral Sclerosis Proportion: A Literature Review and Meta-analysis

Background and Objectives

Amyotrophic lateral sclerosis (ALS) is a rare neurodegenerative disorder. Familial (fALS) cases are usually reported to constitute 5%-10% of all ALS cases; however, no recent literature review or meta-analysis of this proportion (referred to throughout as "proportion fALS") has been conducted. Our objective was to estimate the proportion fALS by geographic region and to assess the effect of study characteristics on the estimates.

Methods

A comprehensive literature review was performed to identify all original studies reporting the number of fALS cases in an ALS cohort. The results were stratified by geographic region, study design (case series or population-based), and decade of study publication. Subgroup analyses were conducted according to family history criteria used to define fALS. We report pooled estimates of the proportion fALS from random-effects meta-analyses when >2 studies are available and I2 is < 90%; weighted averages and ranges are otherwise presented.

Results

The overall pooled proportion fALS based on a total 165 studies was 8% (0%, 71%). The proportion fALS was 9% (0%, 71%) among 107 case series and 5% (4%, 6%) among 58 population-based studies. Among population-based studies, proportion fALS by geographic region was 6% (5%, 7%; N = 37) for Europe, 5% (3%, 7%; N = 5) for Latin America, and 5% (4%, 7%; N = 12) for North America. Criteria used to define fALS were reported by 21 population-based studies (36%), and proportion fALS was 5% (4%, 5%; N = 9) for first-degree relative, 7% (4%, 11%; N = 4) for first or second-degree relative, and 11% (N = 1) for more distant ALS family history. Population-based studies published in the 2000s or earlier generated a lower pooled proportion fALS than studies published in the 2010s or later.

Discussion

The results suggest that variability in the reported proportion fALS in the literature may be, in part, due to the differences in geography, study design, fALS definition, and decade of case ascertainment. Few studies outside of European ancestral populations were available. The proportion fALS was marginally higher among case series compared with population-based studies, likely because of referral bias. Criteria used to define fALS were largely unreported. Consensus criteria for fALS and additional population-based studies in non-European ancestral populations are needed.

Impact of the National Amyotrophic Lateral Sclerosis Registry: Analysis of Registry-funded Research

OBJECTIVE

This research aims to examine the impact of the National Amyotrophic Lateral Sclerosis (ALS) Registry-funded research activities.

METHODS

Registry-funded research and related publications were identified through the National ALS Registry website, the National Institutes of Health (NIH) Reporter website, and verified by Principal Investigators. Key study characteristics (e.g., study population, sample size) and key impact features (e.g., risk factors) were abstracted and recorded on study abstraction forms. Descriptive statistics were used to analyze the volume, productivity, and findings of the Registry-funded research.

RESULTS

Since 2012, the National ALS Registry funded 21 research projects. Of these, 14 were through extramural research grants and included in the analysis. These studies are often related to environmental, medical conditions, and genetic risk factors. On average, the funded grants produced 1 to 2 publications which were cited 114 times by other researchers. The relative citation ratio averaged 1.81 with a weighted relative citation ratio of 16.28. These studies supported the identification and confirmation of candidate risk factors. Environmental and occupational risk factors typically related to heavy metal exposure (e.g., lead, mercury) and agricultural chemicals (e.g., pesticides, herbicides), and the occupations associated with exposure to these substances were most frequently explored.

INTERPRETATION

The National ALS Registry is a multifaceted research platform, one component of which is funded research. This Registry-funded research fills an essential gap in the overall ALS scientific community as it is difficult to prevent and treat a disease without a deeper understanding of its causes.

A new method for estimating under-recruitment of a patient registry: a case study with the Ohio Registry of Amyotrophic Lateral Sclerosis

We developed a disease registry to collect all incident amyotrophic lateral sclerosis (ALS) cases diagnosed during 2016–2018 in Ohio. Due to incomplete case ascertainment and limitations of the traditional capture-recapture method, we proposed a new method to estimate the number of cases not recruited by the Registry and their spatial distribution. Specifically, we employed three statistical methods to identify reference counties with normal case-population relationships to build a Poisson regression model for estimating case counts in target counties that potentially have unrecruited cases. Then, we conducted spatial smoothing to adjust outliers locally. We validated the estimates with ALS mortality data. We estimated that 119 total cases (95% CI [109, 130]) were not recruited, including 36 females (95% CI [31, 41]) and 83 males (95% CI [74, 99]), and were distributed unevenly across the state. For target counties, including estimated unrecruited cases increased the correlation between the case count and mortality count from r = 0.8494 to 0.9585 for the total, from 0.7573 to 0.8270 for females, and from 0.6862 to 0.9292 for males. The advantage of this method in the spatial perspective makes it an alternative to capture-recapture for estimating cases missed by disease registries.