Although individuals aged 65 and over accounted for 12% of the total population of Japan in 1990, suicides in this age group consisted of 29% of all suicides. The elderly population of Japan is expected to grow rapidly to 24% of the total population by the year 2020, and suicide prevention for the elderly is an urgent mental health problem. Among a total of 1,216 elderly patients who were admitted to the Department of Psychiatry at Tokyo Metropolitan Geriatric Hospital between April 1980 and March 1990, 50 were hospitalized immediately after suicide attempts in order to study their psychosociomedical problems. Because early diagnosis of depression and initiation of proper treatment are indispensable—even if patients do not show obvious depressive symptoms—those who develop persistent somatization and/or delirium should be considered highly suicidal and given special attention. With the cooperation of mental health professionals, it is necessary to educate general practitioners, the public, and the elderly themselves about characteristics of psychiatric disorders and various problems associated with aging. Further research on other elderly Japanese populations, as well as research that examines suicide completion, is needed to confirm the findings of the present study.

Ion exchange and chelate properties of poly(ethyleneimine) resin (PEI) were studied. Adsorption of neucoccin anions (NC−) (maximum 1.7×10−4 mol/g) was greater than that of Crystal Violet cations (CV+) (maximum 0.17×10−4 mol/g), indicating that PEI is an anion exchanger. CV+ adsorption increased with the addition of sodium polyacrylate due to its bridging action between CV+ ions and PEI. Adsorption of CrO42− was confirmed to be much greater than that of NC− ions amounting to 4×10−3 mol/g at a sufficiently concentrated solution of CrO42−. The acid exchange capacity of PEI was found to be about the same as the maximum amount of adsorption of CrO42−. Kinetics of adsorption of CrO42− by PEI was studied at various temperatures. Adsorption followed a bimolecular reaction. Activation energy of 28.03×103 J/mol obtained is a right order of magnitude as an ion exchange adsorption. Chelating adsorption of Fe3+ and Cu2+ ions by PEI studied, the maximum amounts of adsorption being 3.1×10−3 mol/g and 3.3×10−3 mol/g, respectively. The values are greater than those for other synthetic polyethylene polyamine. PEI can be used as an anion and metallic cation adsorbent.

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