Effects of ageing on speed and temporal resolution of speech stimuli in older adults

BACKGROUND: According to previous studies, most of the speech recognition disorders in older adults are theresults of deficits in audibility and auditory temporal resolution. In this paper, the effect of ageing on timecompressedspeech and auditory temporal resolution by word recognition in continuous and interrupted noisewas studied. METHODS: A time-compressed speech test (TCST) was conducted on 30 young and 32 older adults with normalhearing thresholds. Lists of monosyllabic words were used at three time compression ratios. Auditory temporalresolution was determined by measuring the monosyllabic word recognition score (WRS), in the presence ofcontinuous and interrupted noise, at three signal-to-noise ratios (S/Ns). RESULTS: There was a significant difference in TCST scores at the three compression ratios within and betweenyoung and older adult none (p< 0.001). Similar results were obtained in WRSs at the three S/Ns in the presenceof interrupted and continuous noise (p< 0.001), and in the degree of auditory temporal resolution(p=0.007). A significant correlation was found between the level of test difficulty of TCST with WRSs in bothyoung (r = 0.549, P=0.002) and older adults (r= 0.531, P=0.003). CONCLUSION: Our results showed that ageing remarkably affects the processing of fast speech stimuli and temporalresolving ability. These results are more supportive of the effect of ageing on speech perception than onloss of hearing.