Incidence of Voice Disorders among Private School Teachers in Taiwan: A Nationwide Longitudinal Study

Background: Teachers are more likely to use a loud voice at work than the general working population, but few longitudinal studies have been conducted on their risk of voice disorders. The occurrence of voice disorders in private school teachers was assessed by using the Longitudinal Health Insurance Database 2000 of Taiwan, which contains information on a random sample of 1 million beneficiaries of National Health Insurance. Methods: This study included private school teachers who were under 35 years old and newly employed between 2000 and 2010, and used workers with other occupations as the comparison cohort. Patients with voice disorders were identified using diagnostic codes on insurance claims. Cox proportional hazards regressions were applied to obtain relative risk estimates. Results: After adjusting for age, sex, income, and comorbidities of sinusitis and laryngitis, private school teachers had a higher risk of developing voice disorders (hazard ratio [HR] = 1.58; 95% confidence intervals: 1.43-1.75). In addition, the finding that elementary and high-school teachers had a higher risk than college teachers (HR: 2.56 vs. 1.44) and the pattern of increases in cumulative incidence over time supported a dose-response relationship between teaching and voice disorders. Conclusions: Private school teachers had higher risks of voice disorders. The results support the causality between occupation and voice disorders in teachers.