中耳機能10年間の推移-老化に関する長期縦断疫学研究より The ten-year transition observed in middle ear analyses -from National Institute for Longevity Sciences Longitudinal Study of Aging
中耳の加齢変化は、解剖学的には鼓膜弾性、耳小骨筋、腱、靱帯の剛性、連鎖可動性等に現れるとされるが、個人差が大きく一致した見解はない。今回、中高年地域住民について、中耳機能の推移について検討を行った。10年の測定間隔の前後で評価できた950名［解析1)］と、1回以上の繰り返し参加を含む3333名［解析2)］を対象として、static admittance（静的コンプライアンスに相当）とピーク圧、共振周波数 (RF) の中耳機能3指標を解析した結果、10年前後の測定値相互に相関がみられ、10年では個体の特徴が保たれていた。解析1) と2) のRFで、stiffnessが高齢で軽微ながら増加または減少という、二つの相反する結果となり、加齢により、中耳stiffness減少と増加をもたらす、相反する解剖学的変化が個体ごとに様々な程度で混在して方向性が一貫しないことが、中耳加齢の特徴であると推察された。
Anatomical studies in humans have reported changes in the middle ear with age, however, the functional changes with age remain an open issue. In the present study, we analyzed the data from the National Institute for Longevity Sciences - Longitudinal Study of Aging (NILS-LSA) to assess the ten-year transition observed in tympanometric measurements. We analyzed the static admittance (comparable to compliance: SC), tympanometric peak pressure (PP), resonance frequency (RF), as variables associated with middle ear function, in 950 subjects who participated in both the 1st (1997-2000 survey) and 6th (2008-2010 survey) investigation of the NILS-LSA [Analysis 1], subsequently, in 3333 subjects who took part in the NILS-LSA between 1997 and 2010, regardless of repetitive visits [Analysis 2]. In Analysis 1, statistical analysis was done to treat the follow-up values at the 6th survey, as a dependent variable, using a multiple regression model in which independent variables were age, sex, and the initial values at the 1st survey. In Analysis 2, repeated measures analysis of variance was performed using a mixed model. The follow-up values in SC, PP, and RF obtained at the 6th survey were significantly correlated with values at the 1st survey in Analysis 1 (p< 0.0001). It suggested that the individual features of middle ear function were not much different from those of a decade ago. However, the direction of aging effect on RF observed in Analysis 1 and Analysis 2 appeared to be incompatible. Whereas in Analysis 1 higher RF was seen in the older middle ear, in Analysis 2 chronological change was directed towards lower frequency. The present finding could be explained by previous studies showing anatomical changes inconsistent for age-related middle-ear stiffness, such as more rigid, and less elastic changes with age in ossicular joints and in the tympanic membrane, and also a reduction in tonic middle-ear muscle contraction, which all affect middle-ear stiffness. As these anatomical changes contribute to middle ear in varying degrees over time, middle-ear stiffness with age may become increased or decreased at an individual level.
- Otology Japan
Otology Japan 22(3), 223-230, 2012-07-25
THE JAPAN OTOLOGICAL SOCIETY