全国高齢難聴者数推計と10年後の年齢別難聴発症率―老化に関する長期縦断疫学研究（NILS-LSA）より

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The number of hearing-impaired elderly people in Japan remains to be clarified. In the present study, we analyzed the data from the National Institute for Longevity Sciences-Longitudinal Study of Aging (NILS-LSA) to ascertain the prevalence and 10-year incidence of hearing loss in Japanese elderly people. Hearing loss prevalence was calculated based on 2,194 subjects who had been included in the 6th survey of the NILS-LSA (2008-2010) and was represented as crude rates (calculation A) and as rates after the exclusion of occupational noise-exposure and ear disease history (calculation B). Estimates of hearing loss incidence were performed at a national level based on demographic statistics. Subsequently, we analyzed the 10-year incidence in 465 subjects showing no hearing loss at baseline (1997-2000 survey) all of whom also participated in the 6(th) survey of the NILS-LSA (2008-2010). The prevalence of hearing loss greatly increased after the age of 65 years. The prevalence observed in calculation A was 43.7%, 51.1%, 71.4%, and 84.3% in men aged 65-69, 70-74, 75-79, and over 80 years old, respectively. In women, the prevalence for the same age groups was 27.7%, 41.8%, 67.3%, and 73.3%, respectively. The size of the hearing-impaired population older than 65 years old was estimated to be 16,553,000. The 10-year incidence rates of hearing impairment in the 60-64- and 70-74-year-old age groups were 32.5% and 62.5% (age at baseline), respectively. These rates rapidly increased with age, although a number of elderly people with good hearing were also observed. Age-related hearing loss is an issue of national importance. These results also indicated that it is possible to preserve good hearing into later in life, and that hearing loss in the elderly may be preventable.