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 the results of deficits in audibility and auditory temporal resolution. In this paper, the effect of ageing on timecompressed speech and auditory temporal resolution by word recognition in continuous and interrupted noise was studied. Methods: A time-compressed speech test (TCST) was conducted on 30 young and 32 older adults with normal hearing thresholds. Lists of monosyllabic words were used at three time compression ratios. Auditory temporal resolution was determined by measuring the monosyllabic word recognition score (WRS), in the presence of continuous 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 between young and older adult groups (p< 0.001). Similar results were obtained in WRSs at the three S/Ns in the presence of 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 both young (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 temporal resolving ability. These results are more supportive of the effect of ageing on speech perception than on loss of hearing.