Prof Michael Swash, Emeritus 

Professor of Neurology & Hon Consultant Neurologist, The Royal London Hospital

血中濃度測定がただ一度しか行われていないこと、過去の暴露物質を被験者の記憶に頼っている点が問題です。環境中の毒物とALSとの関連は古くから指摘され、鉛中毒、ポリオ、外傷性の脳損傷、栄養失調などが原因ではないかともされてきましたが、過去に遡って原因を探ることは容易ではありません。研究チームは、一連の神経変性疾患として、枠を広げてパーキンソン病なども加えた方がよいのかもしれません。遺伝的に、環境毒素への暴露でALSを発症しやすいヒトがいる可能性は否定できず、その点は興味深いと考えます。

原文

“This is a well-conducted study but, as noted in the accompanying editorial caution must be applied when interpreting the results. The study suggests that environmental chemical pollutants, insecticides etc., may be risk factors when coupled with genetic predisposition. This is a reasonable conclusion to draw, but one that is very difficult to test. One should remember that ALS was recognised in the nineteenth century, with the advent of neurology as a formal medical discipline, long before any of these compounds were synthesised or available.

“One limitation with the methodology is that all blood measurements were made only once yet the conclusion relates to life-time exposure – surely a major problem, although difficult to avoid. Another major problem, as with all retrospective epidemiological studies of ‘risk factors’, is recall bias, which may affect how participants remember exposure to the substances investigated. The authors of the report acknowledge this problem, which is itself non-addressable

“There is a long history of wondering if environmental toxins might cause ALS or induce it or modify its natural history beginning in the 19th century, when bodily trauma recalled in retrospective enquiries, lead poisoning, previous poliomyelitis, traumatic brain injury, electrical injury (electricity was new at that time) and dietary imbalances were suggested as causative. These suggestions were often accompanied by large case series, all uncontrolled. Although the authors have included a matched group of non-ALS subjects as controls one would have liked to see included a group of ‘disease controls’, e.g. Parkinson disease, as an additional control group. Overall, nonetheless, the possibility of a modest effect of environmental toxin exposure in the pathogenesis of ALS in (presumably) genetically susceptible people remains an intriguing possibility."