Associations of self-reported and objectively measured physical activity and amyotrophic lateral sclerosis risk

The role of physical activity in the risk of amyotrophic lateral sclerosis (ALS) is debated. It is also unclear whether the association differs in people at high genetic risk of ALS.

The strength and shape of the association between self-reported and device-measured physical activity and incident diagnosis of ALS in the UK Biobank cohort was analysed using Cox regression, adjusting for potential confounders. Cubic splines were used to assess non-linearity. Analyses were performed in the entire cohort and restricted to those with increased genetic risk due to C9ORF72 expansion carriage or C-allele homozygosity at rs12608932 in UNC13A.

Among 384 836 participants with valid questionnaire data, the median age at recruitment was 57.0 years (IQR 50.0-63.0) and median follow-up was for 14.0 years (IQR 13.3-14.6), with 541 incident diagnoses of ALS. Higher self-reported physical activity was associated with a lower risk of ALS (HR_{high vs low}=0.77, 95% CI 0.61 to 0.96). The relationship was non-linear, with lowest risk in those in the mid-range self-reported activity. Higher overall device-measured activity was also associated with a lower risk of ALS (HR_{per 1SD} = 0.75, 95% CI 0.58 to 0.97, n=96 570, 98 ALS events) but with a linear dose-response relationship. The association of physical activity with ALS was similar in individuals with C-allele homozygosity at rs12608932 in UNC13A and directionally consistent but not statistically significant in C9ORF72-HRE carriers (n=535, 56 ALS events).

Higher self-reported and device-measured overall physical activity were associated with a lower risk of ALS overall, but with a potentially non-linear dose-response relationship.