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

Figures & data

Figure 1. Geography of Koza/Kozagawa/Kushimoto area and Oshima, and distribution of patients with ALS. Patients with ALS between 1960 and 1969 (period I: ), between 1970 and 1979 (period II: Δ): between 1980 and 1989 (period III: □), between 1990 and 1999 (period IV: ☆), and between 2000 and 2009 (period V: ▪) were plotted. *: ALS/PDC

Table I. Patients with ALS in the K. area, including Oshima in each period.

	Population^&			ALS patients matched for the selection criteria
Period	Overall K area	Oshima	Total ALS patients enrolled (n)	Overall K area	Oshima	Age at onset Mean (S.D.)	M/F ratio	FH n (%)
I	18,251^#	2,823	7	7	0	56.1 (10.8)	2.5	0 (0)
II	32,128	2,095	12	10	0	55.3 (10.6)	1.5	1 (10)
III	29,732	1,756	4	2	0	59.0 (7.1)	2.0	0 (0)
IV	26,405	1,508	11	9	0	57.7 (11.5)	2.0	3 (33)
V	23,357	1,279	16	15	3	67.6 (12.3)*	0.88	2 (13)
Total			50	43	3		1.53	6 (14.0)

K.: Koza/Kozagawa/Kushimoto area; M/F: male/female ratio; FH: familial history.

^&: populations in 1965, 1975, 1985, 1995 and 2005 census.

^#: Koza/Kozagawa area.

*: p < 0.01 when compared with the mean age at onset in period I.

Figure 2. Changes in incidence of ALS in the overall Koza/Kozagawa/Kushimoto (K.) area and Oshima between 1960 and 2009. Comparing the incidence by the periods, the age- and gender-adjusted incidence of ALS in the overall K. area for the 2005 Japanese population was 5.47/100,000 (95% CI 1.86–9.08), male: 8.29/100,000 (95% CI 1.84–14.73), female: 2.98/100,000 (95% CI–0.69–6.66) in period I, markedly decreased to 0.61/100,000 (95% CI–0.28–1.50), male: 1.36/100,000 (95% CI–0.58–3.30), female: 0 in period III, but recently increased again to 4.39/100,000 (95% CI 1.70–7.07), male: 4.01/100,000 (95% CI 0.22–7.81), female: 4.71/100,000 (95% CI 0.93–8.49) in period V.