Death from cancer among intellectually disabled persons in Japan

Abstract

BACKGROUND: It is important to know the causes of death of intellectually disabled (ID) persons, but there have been few reports about them in Japan.

MATERIALS AND METHODS: The numbers of deaths due to the diseases of the large classification of the ICD10 (Chapters 1-14) in 2005 in 5-year age categories were obtained from the vital statistics of Japan (excluding Chapters 15-22; i.e., external causes, etc.). The numbers of persons in 2005 in 5-year age categories were obtained from the census of Japan. Based on these data, the general mortality rates of the diseases were calculated. The numbers of ID persons in 5- and 10- year age categories in 2005 were obtained from the report of the Ministry of Health, Labor and Welfare of the Japanese Government. Multiplying the general mortality rates by the numbers of ID persons, and summing these products, the expected number of each of the diseases in the ID population was obtained. The expected percentage of each of the diseases in the ID population was calculated and compared with the data previously reported by Souma et al on 72 ID persons who died in a facility for ID persons from 2001 to 2010 on an age-adjusted basis.

RESULTS: (1) In 2005 in Japan, the percentage of those who were 65 years of age or older (seniors) in the general population was 20.1%. In contrast, the total number of ID persons was 406,800, and that of seniors was 15,300 (only 3.8%). (2) Since the expected percentage of deaths due to cancer in the ID population was 37.8%, the expected number in the 72 ID persons was 27.25. However, the reported number was 10. The difference between these 2 numbers (27.25 vs 10) was significant (p < 0.01, chi-square test). Since the expected percentage of diseases of the respiratory system in the ID population was 14.3%, its expected number in the 72 ID persons was 10.3. However, the reported number was 31. The difference between these two numbers (10.3 vs 31) was also significant (p < 0.01).

CONCLUSIONS: The percentage of deaths due to cancer among ID persons was significantly low, and that of respiratory system diseases was significantly high, which was similar to findings in western countries. It is possible that some ID persons also have physical disabilities that make the risk of aspiration pneumonia higher, lead to premature death and, as a result, may make the percentage of cancer deaths relatively low.