Birthweight and the risk of childhood sensorineural hearing loss.

The aim of this study was to estimate the impact of birthweight on the risk of sensorineural hearing loss in children. The study was a nested case-control study. Cases (n = 327) were identified through the Norwegian county registers of children with hearing loss, and controls (n = 391 992) were all children without hearing loss born in the same counties, identified through the Norwegian Medical Birth Registry of Norway. Case definition was mean sensorineural hearing loss (MHL) > or =35 decibel (dB) hearing level (HL) in the better-hearing ear averaged over the pure-tone hearing thresholds at 500, 1000 and 2000 Hz, diagnosed before the age of 5 years. Birthweight <1500 g, as compared with 3500-3999 g, gave an adjusted odds ratio for sensorineural hearing loss of 6.3 [95% CI 2.4, 16.4], controlled for gestational age, gender, parity, maternal age and concurrent birth defects. The risk of hearing loss decreased with increasing birthweights, with adjusted odds ratios of 4.4, 3.8, 1.7 and 1.4 for the birthweights 1500-1999, 2000-2499, 2500-2999 and 3000-3499 g respectively. The risk of both mild to moderate (MHL 35-70 dBHL) and severe/profound hearing losses (MHL >70 dBHL) were influenced by birthweight.