Incidence and geographical variation of amyotrophic lateral sclerosis (ALS) in Southern Germany--completeness of the ALS registry Swabia

Abstract

Objective of this paper was to investigate the incidence, potential geographical clusters and the completeness of the amyotrophic lateral sclerosis (ALS) registry in Southern Germany (Swabia). Age-standardized incidence rates (ASR) and ratios (SIR) as well as 95% confidence intervals (CI) were estimated at county level. Capture-recapture (CARE) procedures were applied taking data source dependency into account to estimate the quality of case ascertainment in the ALS registry Swabia. We identified 438 ALS cases (53% men, 47% women) in the target population of about 8.4 Mio inhabitants. The gender ratio (men∶women) was 1.1∶1. The mean age at onset of ALS was 63.8 (SD = 11.9) years for men and 66.0 (12.2) for women. The age distribution peaked in the age group 70-74 years. The ASR of ALS was 2.5 per 100,000 person years (PY; 95% CI: 2.3-2.7). The mean SIR was 1.1 per 100,000 PY (95% CI: 1.0-1.2). High SIR suggesting geographical clusters were observed in two counties (Göppingen and Bodenseekreis), but the variation was not statistically significant (p-values = 0.2 and 0.5). The percentage of CARE estimated missing cases was 18.9% in the registry yielding an ASR of 3.1 per 100,000 PY. The high coverage of the CARE estimated completeness of the ALS registry Swabia indicates excellent quality for future projects. Regional variations have to be investigated further.

Figure 1. Comparison of age standardized incidence rates of ALS registry data at county level with the exact European populations.

Figure 2. Age standardized incidence ratios of ALS registry data at county level.

Abbreviation and explanation: significant counties (light green: ‘Confidence Interval’ CI below the cut-off value of 1 means less observed cases as expected; dark red: CI above the cut-off value means more observed cases as expected), not significant counties are displayed in dark-green and light red.

Figure 3. Data source intersections of the ALS cases in Southern Germany. Abbreviation: MCC Medical Care Centers. Other Intersections: (1),(3),(4) = 2; (1),(3) = 91; (1),(4) = 95; (1),(2),(4) = 31;