Increasing Incidence and Age at Onset of Amyotrophic Lateral Sclerosis in Nagano Prefecture, Japan

抄録

Background : A recent increase in the incidence of amyotrophic lateral sclerosis (ALS) has been reported in several countries. A similar trend was suspected for Nagano prefecture in Japan. Thus, we retrospectively examined the incidence of ALS and the characteristics of ALS patients at Shinshu University Hospital.
Methods : From hospital clinical records,we identified and enrolled 199 patients with ALS diagnosed based on the El Escorial criteria during the period 1985-2014. The 30-year period was divided into six terms of 5 years each. The incidence of ALS, sex ratio, subtype (limb-or bulbar-onset ALS), and age at onset (＜65 or ≥65 years) were investigated separately for each term.
Results : The incidence of ALS significantly increased in the two most recent terms (2005-2009 and 2010-2014) overall, and in both men and women. A significant difference in mean age at onset was observed in the two most recent terms as compared with the first term (1984-1989). The increase in age at onset was particularly notable in the women with bulbar-onset ALS. No significant change was found in the proportion of ALS patients who were residents of the Matsumoto medical service area as compared with those from other areas.
Conclusion : We confirmed that the incidence of ALS in Nagano prefecture has been recently increasing. Furthermore, the ratio of patients with older-onset ALS has recently increased because of the chronological increase in age at onset of ALS patients.