All ETDs from UAB

Advisory Committee Chair

Gerald McGwin Jr

Advisory Committee Members

Stacey Cofield

Nalini Sathiakumar

W Dana Flanders

Mary Jean Brown

Document Type

Dissertation

Date of Award

2012

Degree Name by School

Doctor of Philosophy (PhD) School of Public Health

Abstract

Hearing loss is one of the most common major abnormalities present among infants. Two to four infants per 1,000 are born in the United States with severe-to-profound newborn hearing loss (Chu 2003). Undetected, hearing loss delays speech, language, and cognitive development. Numerous studies have shown that prenatal lead exposure is associated with a variety of neurobehavioral and electrophysiological abnormalities (Abbate 1995, Bellinger 2004, Koller 2004). Studies focusing on hearing have primarily described pediatric cases or occupationally exposed adults where blood lead levels (BLLs) are much higher than currently seen in the United States (Otto 1985; Bleecker 2003; Schwartz 1987). Hearing impairment studies among lead-exposed infants have been few and inconsistent (Rothenberg 1994; Counter 1997; Buchanan 1999). Because of inconsistent results from previous studies and because most studies did not consider hearing outcome measures among infants, we conducted two studies to evaluate the association of low-level prenatal blood exposure and auditory brainstem response (ABR) among infants. ABR is a neurologic test of auditory brainstem function in response to auditory stimuli recorded by placing electrodes on the scalp. The first study assessed the relationship between infant wave V marked latencies at 60 and 70 decibel (dB) normal hearing level (nHL) and prenatal blood lead exposure among 107 women-infant pairs with umbilical cord blood lead analyzed at two New York City hospitals. Infants exposed prenatally to lead did not show significantly prolonged wave V marked peak latencies. The second study examined the relationship between infant wave V hearing threshold patterns at 500 Hertz (Hz), 2kHz, and 4kHz stimulus frequencies and maternal prenatal blood lead exposure among 107 infants at two New York City hospitals. Umbilical cord BLL was not significantly associated with hearing thresholds at any of three stimulus frequencies. Overall, we found no association between prenatal lead exposure and various infant hearing outcomes. These studies represent interim analyses conducted on a portion of the full cohort, which is still being followed, so results should be interpreted with caution. Future analyses are planned on the full cohort, and the findings may change.

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