Author response to a Letter to the Editor entitled: Preventive effect of coffee and tea on amyotrophic lateral sclerosis

We thank Dr Kawada for highlighting the results of our case-control studies (1,2) that suggest a preventive effect of coffee and tea on ALS risk. Our data find support from the consistency of the results from two independent studies and the purported mechanism of the association, derived from animal and cell models (3). In addition, the analogy of the results from studies in patients with Parkinson’s disease and, to some extent, with Alzheimer’s disease (4,5) enforces the positive effects of caffeine and other coffee derivatives against neurodegeneration. However, we also convene with Dr Kawada that the results of our studies were not confirmed by a large multi-cohort study that used mortality for ALS among exposed and unexposed individuals (6). As acknowledged by the authors, the use of ALS mortality as a proxy for the incidence of the disease could lead to an underestimation of the risk, the educational level of the cohort was high and not truly representative of the underlying populations, and measurement errors in estimating caffeine intake could not be excluded. As no definite conclusions can be drawn from the present findings on the protective role of coffee against ALS and other neurodegenerative diseases, we convene with Dr Kawada on the need to plan and undertake a prospective study comparing coffee users and non-users, measuring the quantity of caffeine intake, and assessing the incidence of ALS, Parkinson’s and Alzheimer’s disease during follow-up among exposed and unexposed individuals.