Hearing loss is associated with decreased nonverbal intelligence in rural Nepal.

Abstract

To evaluate the association between adolescent and young-adult hearing loss and nonverbal intelligence in rural Nepal. Cross-sectional assessment of hearing loss among a population cohort of adolescents and young adults. Sarlahi District, southern Nepal. Seven hundred sixty-four individuals aged 14 to 23 years. Evaluation of hearing loss, defined by World Health Organization criteria of pure-tone average greater than 25 decibels (0.5, 1, 2, 4 kHz), unilaterally and bilaterally. Nonverbal intelligence, as measured by the Test of Nonverbal Intelligence, 3rd Edition standardized score (mean, 100; standard deviation, 15). Nonverbal intelligence scores differed between participants with normal hearing and those with bilateral (p = 0.04) but not unilateral (p = 0.74) hearing loss. Demographic and socioeconomic factors including male sex; higher caste; literacy; education level; occupation reported as student; and ownership of a bicycle, watch, and latrine were strongly associated with higher nonverbal intelligence scores (all p < 0.001). Subjects with bilateral hearing loss scored an average of 3.16 points lower (95% confidence interval, -5.56 to -0.75; p = 0.01) than subjects with normal hearing after controlling for socioeconomic factors. There was no difference in nonverbal intelligence score based on unilateral hearing loss (0.97; 95% confidence interval, -1.67 to 3.61; p = 0.47). Nonverbal intelligence is adversely affected by bilateral hearing loss even at mild hearing loss levels. Socio economic well-being appears compromised in individuals with lower nonverbal intelligence test scores.