Body Mass Index in Amyotrophic Lateral Sclerosis – Results from the ALS Registry Swabia

Introduction:

Most commonly clinically manifest Amyotrophic Lateral Sclerosis (ALS) is associated with weight loss. However currently no data are available to describe the life course history of pre-diagnostic body mass index (BMI) in patients with ALS.

Methods:

We evaluated

data from a population-based case-control study embedded in the ALS Registry Swabia and analyzed 393 ALS patients (mean age: 65.8 years, 57.3% men) and 791 age and sex matched controls. Differences of BMI change in cases and controls over time were modeled using a multilevel additive model. In addition, survival in ALS cases by BMI change before interview was modeled using accelerated failure time models adjusted for other prognostic factors.

Results:

At interview, BMI in cases was 1.7 kg/m² lower than in controls. BMI in controls during 20 to 70 years before the interview was consistently higher than in ALS cases. E.g. conditional logistic regression revealed an odds ratio of 1.05 (95% confidence interval (CI) 1.00 – 1.11, p = 0.041) per 1 kg/m² higher BMI 35 to 45 years before interview. Notably, a sharp kink in BMI of ALS cases was evident about 10 years before disease onset. In ALS cases, weight loss was strongly associated with shorter survival. Stable weight in ALS cases showed a median survival time of 22.1 months (95% CI: 19.2 – 25.0 months), weight loss of 2.5 kg/m² over the last three months of 13.4 months (95%-CI: 10.5 – 16.3 months). This effect was independent of the current BMI value at interview.

Conclusions:

Our data suggest a possible association of BMI with ALS which reveals higher risk decades before clinical manifestation of ALS, but shows a sharp kink in ALS cases about 10 years before disease onset. Also, in ALS cases, stronger weight decrease is associated with poorer prognosis. These results may point to a potential different role of the metabolic state in disease risk and disease prognosis.