An increase in ALS incidence on the Kii Peninsula, 1960-2009: a possible link to change in drinking water source.

We investigated changes in the incidence of amyotrophic lateral sclerosis (ALS) in the Koza/Kozagawa/Kushimoto area (K. area) in the Kii Peninsula, Japan in 1960-2009. Probable and definite ALS cases diagnosed using El Escorial criteria were collected during a five-decade period: period I-V, 1960-2009. Forty-three ALS patients matched the selection criteria in the overall K. area, including three patients on Oshima, a small island opposite the mainland K. area. The age- and gender-adjusted incidence of ALS in the overall K. area (standardized for the 2005 Japanese population) decreased from 5.47/100,000 (95% CI 1.86-9.08) in period I to 0.61/100,000 (95% CI-0.28-1.50) in period III, and then increased to 4.39/100,000 (95% CI 1.70-7.07) in period V. On Oshima, the age- and gender-adjusted incidence of ALS was 9.45/100,000 (95% CI-7.39-26.29) in period V. The present research indicates an increase of ALS incidence in the K. area, especially on Oshima. A limitation of this study was the small population.

Survival rate of patients with amyotrophic lateral sclerosis in Wakayama Prefecture, Japan, 1966 to 2005.

To investigate longitudinal changes in the survival rate of patients with amyotrophic lateral sclerosis in Wakayama Prefecture, Japan, we made a retrospective hospital-based study of 454 patients diagnosed with motor neuron disease (MND) at Wakayama Medical University (WMU) Hospital between 1966 and 2005. Of the 454 patients, 240 who were born and who lived in Wakayama Prefecture were diagnosed with definite or probable ALS during this period, according to the El Escorial criteria. The clinical data of the 240 patients, including sex, birth date, birthplace, address, age at onset, initial symptoms, date when respiratory support was applied (tracheostomy, noninvasive positive pressure ventilation, or mandatory artificial ventilation), and date of death were reviewed retrospectively. The age at onset of patients who developed initial symptoms before 1990 was 53.4+/-10.6 (mean+/-S.D.) and that in 1990 or thereafter was 64.8+/-10.3, respectively, showing a significant difference (p<0.0001). Clinical duration was determined from onset to either date of death or initiation of respiratory support in this study. Survival rate was compared using the Kaplan-Meier method according to age at onset, sex, initial symptoms and year of onset. Mean age at onset shifted towards older age according to a later year of onset, due to the overwhelming senility rate in Wakayama Prefecture. Older onset patients had a significantly poorer survival rate than younger onset patients when it was compared based on 10-year age groups (log rank, p<0.0001). Male patients had a poorer survival rate than female patients (p<0.0001). ALS patients with bulbar palsy onset showed shorter clinical durations than those with lower leg onset (p<0.0071, Breslow-Gehan-Wilcoxon test). Patients over 70 years old more frequently showed bulbar palsy onset compared to those younger than 69 (p=0.003). In a comparison of year of onset before and after 1990, ALS patients after 1990 had characteristics of older age onset and shorter clinical duration, and more frequently showed bulbar palsy onset compared with those before 1990. These findings indicated that younger onset patients with ALS decreased after 1990 in Wakayama Prefecture and this might partly explain the recent decline of ALS incidence in Wakayama Prefecture. The shift of the mean age at onset to older age might be due to exogenous factors, including changes in lifestyle, food, and drinking water in this area. Bulbar palsy onset and age at onset were expected as predictors of the survival rate.

[Changes in the incidence and clinical features of ALS in the Koza, Kozagawa, and Kushimoto area of the Kii Peninsula--from the 1960s to the 2000s (follow-up study)].

In the 1960's, ALS was highly prevalent in the southern part of the Kii Peninsula, especially in the Koza, Kozagawa, and Kushimoto area (K area). Thereafter, the incidence of ALS was considered to have gradually decreased, and the disease almost disappeared in the 1980's. However, new patients have been continuously identified in this area, and indicating the importance of studying the changes in the incidences of ALS. This study investigated the characteristic clinical features and incidence of ALS in K area during the following periods: period I: between 1967 and 1971, period II: between 1989 and 1999, and period III: between 2000 and 2008. Data on all patients with motor neuron disease were collected for each year within these periods from medical doctors and medical staff of the regional public health center and municipal office. Neurologists on our research team examined and assessed each of these patients on the basis of the El Escorial criteria. Probable and definite ALS patients diagnosed by neurologists using the El Escorial criteria in K area during the research periods were collected. The crude incidence rate of ALS in K area were similar in period I, i.e. 6.0/100,000, and in period III, i.e., 5.7/100,000. The age-, and sex-adjusted incidence (considering the 2000 census) in women in K area during period III, especially in Kozagawa district, was higher than that in periods I and II. The adjusted incidence rate in Kozagawa district was 8.8/100,000, and was higher than that in other areas of the world. The clinical features of patients in this area were quite similar to those of patients with classical ALS. Five patients from 3 families with a family history of ALS and 2 patients without a family history presented with the clinical features of ALS and PDC during these research periods. The mean age at onset for period III was higher than that in period I (p < 0.01). The frequency of ALS patients with upper-extremity onset in period III was lower than that in period I (p = 0.05), whereas the frequency of patients with bulbar-onset has recently increased. Conclusion The result of present study indicate that the recent incidence of ALS in K area is high, the age of onset has recently become higher and the number of bulbar-onset patients has increased. All the abovementioned findings could be attributed to an increase in the senility rate in the population. Between 2000 and 2008, the age-adjusted incidence in ALS for women in K area, especially in the Kozagawa district, was high, indicating an increase in that the incidence of ALS among women in this area after 2000. The factors responsible for the high incidence of ALS in this area remain to be clarified.