Hearing in advanced age Epidemiological, pathophysiological, and diagnostic perspectives from the Gothenburg H70 Birth Cohort Studies

Sammanfattning: The population aged 80 and above is expected to increase in the future resulting in an anticipated rise in health care demands. Age-related hearing loss (ARHL) is described as the third most common health condition associated with ageing. ARHL often results in communication difficulties and social isolation and is associated with cognitive decline. Ageing processes affect both the peripheral and the central auditory systems. Age-related deterioration in the central parts of the auditory pathways often results in severe communication difficulties. It is important to study the prevalence of ARHL, including age cohort differences, in order to assess rehabilitation needs. However, to gain a deeper understanding of ARHL and its associated care needs, it is essential to conduct studies that incorporate pathophysiological aspects of ageing in the auditory system. A limited amount of research has been carried out in this area in evolving populations 80 years and older. This thesis focuses on epidemiological, pathophysiological, as well as diagnostic perspectives of ARHL in 85-year-old men and women. The results are based on a prospective and epidemiological study, The Gothenburg H70 Birth Cohort Studies. The specific papers within this thesis explore different aspects of ARHL. Paper I presents pure-tone audiometry results, which predominantly reflect peripheral hearing. The findings indicate that men have better hearing at low frequencies but poorer hearing at high frequencies compared to women. Additionally, the study examines hearing decline longitudinally between the ages of 75 to 85, revealing a significant decline at mid-high frequencies for both sexes. Paper II also focuses on peripheral hearing loss and highlights differences in pure- tone hearing between two birth cohorts of 85-year-olds, born approximately 30 years apart. The prevalence of ARHL was found to have decreased over approximately three decades among 85-year-old men but remained unchanged vi in women. Paper III describes pathophysiological aspects of ARHL. Test results describe various validated and clinically utilized auditory measures, including speech audiometry, and suggest that sensorineural hearing loss, related to cochlear damage, is the most common subtype of auditory dysfunction in 85-year-olds. Only a few participants had conductive hearing loss (~6%), reflecting middle-ear pathologies. Additionally, almost one-fifth of the 85-year-olds had poor speech recognition in relation to a SII-based algorithm based on pure-tone thresholds as well as supra-threshold factors. Based on the criteria used in this study, poor speech recognition was only occasionally (~2%) attributed to auditory nerve dysfunction. Paper IV investigates central auditory function, specifically binaural listening skills in 70- and 85-year-olds. Central auditory function was studied using a simplified dichotic digit test (DDT) with the use of one-pair digits, which imposes a relatively low cognitive and linguistic load on participants. The results showed that older age was associated with poorer DDT scores. Furthermore, the outcome of the DDT was influenced by both peripheral hearing loss, including high frequency hearing loss, and cognitive abilities. This makes it difficult to identify isolated central auditory processing disorders using DDT in advanced age.