Recent Trend Toward Decrease in the Incidence of Childhood Type 2 Diabetes in Tokyo
We previously reported that the annual incidences of children with type 2 diabetes as detected by urine glucose screening at school in Tokyo during 1981–1995 were significantly higher than the incidence in 1974–1980 (1). We evaluated recent changes in the annual incidence of childhood type 2 diabetes in Tokyo. The results were analyzed using Fisher’s exact probability test.
From 1974 to 2004, a total of 9,242,259 school students were tested for glucosuria to detect diabetes. A total of 236 children were diagnosed as having type 2 diabetes through this screening program. Overall, 83.9% of children with diabetes were obese. The overall incidence was 2.55 per 100,000 per year. Junior high school children had a significantly higher incidence than primary school children (0.75 vs. 6.27 per 100,000; P < 0.0001). The annual incidences over the 5-year periods from 1974 to 2004 were 1.73, 3.23, 3.05, 2.90, 2.70, and 1.41 per 100,000, respectively. The incidence in 1974–1980 was significantly lower than those in 1981–1985, 1986–1990, and 1991–1995 (P = 0.0038, 0.0091, and 0.0226, respectively) and tended to be lower than that in 1996–2000 (P = 0.0672). The incidence in 2001–2004 was also significantly lower than those in 1981–1985, 1986–1990, and 1991–1995 (P = 0.0056, 0.0120, and 0.0194, respectively) and tended to be lower than that in 1996–2000, as well (P = 0.0557). The annual incidences of junior high school children from 1974 to 2004 were 5.25, 7.70, 6.95, 7.16, 5.28, and 3.66 per 100,000, respectively. The incidence of junior high school children in 2001–2004 was significantly lower than that in 1981–1985 (P = 0.0315) and tended to be lower than that in 1991–1995 (P = 0.0622). For the same periods, there was no significant change in the incidence of primary school children. Therefore, the overall trend toward decrease in the incidence of childhood type 2 diabetes in 2000–2004 was most strongly associated with the decrease in that among junior high school children.
After the 1970s, the tendency toward childhood obesity rapidly increased in the 8- to 14-year age-group in Japan, contributing to the increase in childhood type 2 diabetes (2). However, this trend has recently seemed to be weakened. The Ministry of Education, Culture, Sports, Science and Technology of Japan reported a recent trend toward a decrease in the prevalence of obesity among junior high school children (3). Recently, significant concern regarding childhood obesity and associated metabolic disorders has spread in the Japanese population, especially among children and adolescents residing in cities (3). They are likely to ingest fewer sugar-sweetened beverages and snacks as well as fat-rich foods than in the past. In addition, they tend to limit sedentary activities and participate in various sports (3). These lifestyle changes may contribute to the decrease in the incidence of type 2 diabetes in 2001–2004 in the Tokyo metropolitan area.
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