A five-year longitudinal study of hearing in a Danish rural population aged 31-50 years

This paper aims to report changes in hearing sensitivity over five years in a rural population aged 31-50 years and to identify risk factors associate d with hearing deterioration. The study is prospective and based on data fr om pure tone audiometry and questionnaires in the Ebeltoft Health Promotion Project in Denmark. A representative sample of 705 subjects had a complete follow-up, including audiometry. The median hearing deterioration was 2.5 dB at 3-4 kHz and 0 dB at 0.5-2 kHz. There was a high degree of individual variability in deterioration. The overall deterioration of hearing sensitiv ity of the population was largely predicted from the cross-sectional findin gs reported previously. In the analysis of risk factors, hearing deteriorat ion was defined as an average deterioration 10 dB/5 years at 3-4 kHz in at least one ear. Deterioration was present in 23.5% of the sample. The 41-50- year-olds had a relative risk of deterioration of 1.32 (95% CI 1.01-1.73) c ompared with the 31-40-year-olds. Males had a relative risk of 1.35 (1.03-1 .76) compared with females. The risk was not significantly elevated for a r ange of other possible risk factors confirmed by logistic regression analys is. In conclusion, deterioration in hearing sensitivity on population level can be predicted on the basis of cross-sectional findings. Hearing sensiti vity deteriorated mainly at 3-4 kHz. The deterioration increased with age a nd was higher in males than in females. Other risk factors were not found. The present study does not support the hypothesis that hypertension or toba cco smoking is associated with deterioration in hearing.