Markers of inflammatory status are associated with hearing threshold in older people: findings from the Hertfordshire ageing study

Background: age-related hearing loss is a common disabling condition but its causes are not well understood and the role of inflammation as an influencing factor has received little consideration in the literature. Objective: to investigate the association between inflammatory markers and hearing in community-dwelling older men and women. Design: cross-sectional analysis within a cohort study. Setting: the Hertfordshire Ageing Study. Participants: a total of 343 men and 268 women aged 63-74 years on whom data on audiometric testing, inflammatory markers and covariates were available at follow-up in 1995. Main outcome measures: average hearing threshold level (across 500-4,000 Hz) of the worst hearing ear and audiometric slope in dB/octave from 500 to 4,000 Hz. Results: older age, smoking, history of noise exposure and male gender (all P < 0.001) were associated with higher mean hearing threshold in the worse ear in univariate analysis. After adjustment for these factors in multiple regression models, four measures of immune or inflammatory status were significantly associated with hearing threshold, namely white blood cell count (r = 0.13, P = 0.001), neutrophil count (r = 0.13, P = 0.002), IL-6 (r = 0.10, P = 0.05) and C-reactive protein (r = 0.11, P = 0.01). None of the inflammatory markers was associated with maximum audiometric slope in adjusted analyses. Conclusions: markers of inflammatory status were significantly associated with degree of hearing loss in older people. The findings are consistent with the possibility that inflammatory changes occurring with ageing may be involved in age-related hearing loss. Longitudinal data would enable this hypothesis to be explored further.