Abstract
This is a retrospective longitudinal study that uses data from the National Health Insurance Research Database (NHIRD) of Taiwan of which hypothyroid patients who received a diagnosis between 2000 and 2010 were selected and followed up until 2011. The primary outcome of this study was the occurrence of tinnitus (ICD-9-CM code 388.3). The relevant comorbidities were selected as potential confounders according to the literature, which included vertigo (ICD-9-CM code 386), insomnia (ICD-9-CM code 780), anxiety (ICD-9-CM code 300.00), and hearing loss (ICD-9-CM code 388–389). The overall incidence of tinnitus was significantly higher in the hypothyroidism cohort than in the non-hypothyroidism cohort (9.49 vs. 6.03 per 1000 person-years), with an adjusted HR of 1.35 (95% CI 1.18–1.54) after adjusting potential confounders. The incidences of tinnitus, as stratified by gender, age, comorbidity, and follow-up time, were all significantly higher in the hypothyroidism cohort than those in the non-hypothyroidism cohort. The incidence of tinnitus significantly increased with age (aHR = 1.01, 95% CI 1.01–1.02). In conclusion, we report the relationship between hypothyroidism and the increased risk for tinnitus. We also found that hypothyroidism patients are at increased risk of developing tinnitus when associated with comorbidities including vertigo, hearing loss, and insomnia.
Highlights
This is a retrospective longitudinal study that uses data from the National Health Insurance Research Database (NHIRD) of Taiwan of which hypothyroid patients who received a diagnosis between 2000 and 2010 were selected and followed up until 2011
The overall incidence of tinnitus was significantly higher in the hypothyroidism cohort than in the nonhypothyroidism cohort (9.49 vs. 6.03 per 1000 person-years), with an adjusted HR of 1.35 after adjusting potential confounders
This study showed as a secondary outcome that patients with hypothyroidism seem to have an interactional effect with comorbidities including hearing loss, vertigo and insomnia towards the risk of developing tinnitus
Summary
This is a retrospective longitudinal study that uses data from the National Health Insurance Research Database (NHIRD) of Taiwan of which hypothyroid patients who received a diagnosis between 2000 and 2010 were selected and followed up until 2011. The peripheral blood flow is known to be under the control of the thyroid hormones as well The mechanism for this is not very well understood, but may involve modulation of the potassium channels causing changes in the gradient of the Na+/K+ ions across the vascular walls. Another way in which the thyroid controls the blood flow is through changes in the levels of vasoactive hormones released by the vascular e ndothelium[7]. Sympathetic nerve fibers running from the stellate ganglia and superior cervical ganglia has been shown to terminate on the spiral modiolar artery This innervation is partly responsible in how the cochlear vasculature maintains its vascular tone. Activation of the sympathetic nerves will contract the smooth muscle cells
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