[Epidemiological Aspects of Idiopathic Thrombocytopenic Purpura in Kochi Prefecture]

This paper describes the epidemiological aspects of ITP in Kochi prefecture. Five hundred and twenty three patients were newly registered over the past 14 years (from April 1, 1989 to March 31, 2002). They comprised 192 men (36.7%) and 331 women (63.3%), yielding a female to male ratio (F/M) of 1:1.7. The proportions of children (< or = 14 y/o), adults (15-64 y/o) and the elderly (> or = 65 y/o) were 24.9%, 51.6% and 23.5%, respectively, and F/M ratios were 1:0.8 in children, 1:3.0 in adults and 1:1.3 in the elderly, showing elimination of the sex difference in the elderly. Average annual incidences per 100,000 population were estimated by 2 calendar year periods (Period I: '89-'90, II: '91-'92, III: '93-'94, IV: '95-'96, V: '97-'98, VI: '99-'00, VII: '01-'02). The incidence of ITP showed a significant increase over the past 14 years, particularly in the elderly (I: 0.90, II: 0.67, III: 1.89, IV: 3.52, V: 3.05, VI: 4.10, VII: 3.17). The increase of ITP in the elderly concomitant with the increase in the size of the elderly population is probably not only exclusive to Kochi prefecture but also seen throughout Japan, therefore, the establishment of the optimal therapeutic management of ITP in the elderly including the eradication of Helicobacter pylori is required.