Prevalence rates by sex and age group are shown in . The overall prevalence of tinnitus in this cohort was 10.6 percent (95% confidence interval [CI] 9.5-11.6). The prevalence of tinnitus was higher for men than for women (11.9% vs 9.4%, p = .02), and higher for those 55-84 years of age than for younger participants (14.4% vs 9.0%, p < .001). Increasing linear trends in prevalence by age group were statistically significant for men, women, and both sexes (p < .05). Of 345 participants with tinnitus, 91.9 percent rated their tinnitus as moderate (n = 274) or severe (n = 43); the remaining 28 participants reported mild tinnitus that caused difficulty falling asleep. The overall prevalence of tinnitus rated as severe was 1.3 percent. In a logistic regression model including only age and sex, the odds of having tinnitus increased with age (OR = 1.09 for each 5-year increase in age, 95%CI = 1.04, 1.16), and men were more likely to have tinnitus than were women (OR = 1.29, 95%CI = 1.03, 1.62).
Prevalence of Tinnitus by Sex and Age Group, Along with 95% Confidence Interval (CI)
Selected characteristics of this cohort, by tinnitus status, are shown in . In separate age- and sex-adjusted models we also evaluated the associations of these characteristics with tinnitus (). After adjusting for age and sex, most of the characteristics reflecting auditory function and possible injuries were significantly associated with having tinnitus. These included hearing impairment (OR = 3.60, 95%CI = 2.67, 4.84), history of ear infection (OR = 1.98, 95%CI = 1.40, 2.79 for men, but not significant for women), history of ear surgery (OR = 3.72, 95%CI = 1.91, 7.23), history of head injury (OR = 1.94, 95%CI = 1.54, 2.45), history of otosclerosis (OR = 4.35, 95%CI = 1.61, 11.75), occupational noise exposure (ever: OR = 1.50, 95%CI = 1.19, 1.90; past year: OR = 2.00, 95%CI = 1.50, 2.67), possible middle ear effusion (OR = 1.41, 95%CI = 1.01, 1.98), and target shooting (ever: OR = 1.86, 95%CI = 1.37, 2.54; past year: OR = 1.72, 95%CI = 1.11, 2.66). In addition, for each additional loud hobby in which participants had engaged, the odds of having tinnitus increased (ever: OR = 1.15, 95%CI = 1.05, 1.27; past year: OR = 1.13, 95%CI = 1.03, 1.24). Hunting was not significantly associated with having tinnitus.
Participant Characteristics by Tinnitus Status and Associated Odds of Having Tinnitus (Odds Ratio and 95% Confidence Interval)
Depressive symptoms (OR = 2.04, 95%CI = 1.50, 2.76) and the use of anti-depressant medications (OR = 1.58, 95%CI = 1.17, 2.14) were significantly associated with having tinnitus, but the use of anti-anxiety medications was not.
Among the cardiovascular-related risk factors examined, the following were associated with having tinnitus after adjusting for age and sex: history of CVD (OR = 2.14, 95%CI = 1.32, 3.45), history of heavy drinking (OR = 1.34, 95%CI = 1.02, 1.76), obesity (OR = 1.41, 95%CI = 1.11, 1.81), peripheral vascular disease (OR = 2.59, 95%CI = 1.01, 6.65), higher numbers of packyears smoked (11-23 vs 0: OR = 1.57, 95%CI = 1.12, 2.21; 24+ vs 0: OR = 1.43, 95%CI = 1.02, 2.02), and being a current smoker (OR = 1.50, 95%CI = 1.12, 2.01 vs never smoker). A history of arthritis was also associated with having tinnitus (OR = 1.71, 95%CI = 1.32, 2.22). Having consumed alcohol in the past year was negatively associated with having tinnitus for women (OR = 0.54, 95%CI = 0.35, 0.83) but not men. Other cardiovascular-related factors that were not associated with having tinnitus included use of antihypertensive medication, diabetes, history of carotid artery surgery, hypertension, use of NSAID medication, regular exercise, and serum HDL and total cholesterol.
Factors associated with tinnitus in these models were then evaluated in a multivariable model. Results from the final, most parsimonious model, are shown in . Most of the factors remaining in this model were classified under the auditory function/injury category. These included occupational noise exposure (past year: OR = 1.90, 95%CI = 1.38, 2.63), hearing impairment (OR = 3.20, 95%CI = 2.33, 4.38), history of ear infection (for men, OR = 1.75, 95%CI = 1.20, 2.57; but not women, OR = 0.90, 95%CI = 0.62, 1.31), history of head injury (OR = 1.84, 95%CI = 1.40, 2.40) and target shooting (ever: OR = 1.56, 95%CI = 1.09, 2.24). Other factors that remained positively associated with having tinnitus in the multivariable model were depressive symptoms (OR = 1.82, 95%CI = 1.33, 2.51), history of arthritis (OR = 1.46, 95%CI = 1.08, 1.96), and current use of NSAID medications (OR = 1.33, 95%CI = 1.02, 1.75). For women, consuming alcohol in the past year was inversely associated with having tinnitus (OR = 0.56, 95%CI = 0.35, 0.90). There was no linear association between age and tinnitus in this fully-adjusted model, nor was there a significant interaction between age and gender. The interactions between gender and history of ear infection (p = .01) and gender and alcohol consumption (p = .03) were both statistically significant.
Risk Factors Associated with Tinnitus from Final Logistic Regression Model
The model in was repeated with a pure-tone average (PTA) of hearing thresholds at 500, 1000, 2000 and 4000 Hz (worse ear) replacing the hearing impairment classification, and the results were very similar. In that model, participants were 17% more likely to have tinnitus with every 5 dB increase in PTA (OR = 1.17, 95%CI = 1.13, 1.22; complete model results not shown). Similarly, when individual thresholds (at 500, 1000, 2000, 3000, 4000, 6000 and 8000 Hz, worse ear) were substituted for the hearing impairment classification, the 3000 Hz threshold (OR = 1.06 for every 5 dB increase in threshold, 95%CI = 1.01,1.11) and 6000 Hz threshold (OR = 1.09 for every 5 dB increase in threshold, 95%CI = 1.04,1.14) were significantly associated with having tinnitus (complete model results not shown). Based on the Hosmer & Lemeshow test (Hosmer & Lemeshow, 1989
), all three models (using the hearing impairment classification, the PTA, and the individual thresholds) fit the data well; however, the best fitting model used the hearing impairment classification shown in .
Among those with occupational noise exposure in the past year, 53.4% indicated that they ever wore hearing protection at that job. Among those who had regularly participated in target shooting in the past year, 84.7% indicated that they ever wore hearing protection while doing so. After adjusting for age and sex, the use of hearing protection was not significantly associated with tinnitus for either occupational noise exposure (OR = 1.45, 95%CI = 0.82, 2.59) or target shooting (OR = 5.62, 95%CI = 0.72, 43.66).