Low heritability of tinnitus: results from the second Nord-Trøndelag health study.

OBJECTIVE To estimate the heritability of tinnitus. DESIGN Self-report questionnaire data collected from August 1, 1995, through June 30, 1997, from individuals in the Nord-Trøndelag Hearing Loss Study (an integrated part of the Nord-Trøndelag Health Study) were used. The study also included information on first-degree family relationships, and age-corrected polychoric correlations of relatives' tinnitus status were calculated. A structural equation model was fit to the data, and the relative contributions of genes and unique environmental effects were estimated. Models that included sex-specific effects were also tested. SETTING Nord-Trøndelag County, Norway. PATIENTS A population-based sample of 12 940 spouses, 27 607 parent-offspring, and 11 498 siblings was used. A total of 28 066 respondents were tested twice, yielding a test-retest correlation of 0.65 for the report of tinnitus. MAIN OUTCOME MEASURE Heritability of tinnitus. RESULTS Correlations for parent-offspring ranged from 0.01 to 0.07 for the various sex combinations, sibling correlation ranged from 0.06 to 0.14, and the spouse correlation was 0.04. This family correlation pattern implies an upper limit for heritability of 0.11 with no sex differences in the heritability estimates. CONCLUSIONS This is the first large population-based family study, to our knowledge, to report on the heritability of tinnitus. In contrast to previous speculations in the literature, this low heritability indicates that additive genetic effects explain only a small proportion of the variance of tinnitus in the population.