In this prospective study of 26,809 male health professionals, we found no overall association between alcohol intake and the risk of hearing loss. However, among those with lower levels of vitamin B12 intake, consumption of higher levels of alcohol, specifically liquor (spirits), was associated with an increased risk of hearing loss.
Several lines of evidence suggest that alcohol may influence the preservation of hearing function. Disturbances in cochlear blood flow, particularly hypoperfusion and possible ischemia, have been associated with adult hearing loss. (Seidman et al. 1999
) Moderate alcohol consumption may aid in the maintenance of optimal cochlear blood flow, possibly mediated by increased HDL cholesterol or reduced coagulation. In prospective cohort studies, moderate intake of alcohol has been associated with a lower risk for myocardial infarction as compared to abstention, (Maclure 1993
) an association thought to be due to higher levels of HDL cholesterol in moderate drinkers (Linn et al. 1993
) that have been demonstrated in short-term randomized trials of alcohol administration. (Rimm et al. 1999
) Similarly, Gates et al (Gates et al. 1993
) observed an inverse relation between HDL levels and hearing thresholds, suggesting a protective effect of HDL on hearing.
Although chronic alcohol abuse has been associated with hearing impairment, (Rosenhall et al. 1993
) results from studies of the relation between low or moderate levels of alcohol intake and hearing loss have been inconsistent. Several cross-sectional studies have suggested that consumption of moderate amounts of alcohol may have a protective effect. (Fransen et al. 2008
; Helzner et al. 2005
; Popelka et al. 2000
) For example, a cross-sectional study based on audiometric evaluations in participants of the Epidemiology of Hearing Loss Study (n=3571), found an inverse association (OR=0.71) between moderate alcohol use (>140 g/wk) during the previous year and hearing loss [defined by pure tone average as measured by audiometry: PTA (0.5,1,2,4) > 25 dB HL]. This association was even stronger (OR=0.49) when hearing loss was defined according to more stringent criteria [i.e. PTA (0.5,1.2.4) > 40 dB HL]. (Popelka et al. 2000
) A case-control study in Japan reported a U-shaped relation between alcohol consumption and hearing loss, with a 45% decreased risk of hearing loss for occasional drinkers (not defined), a 27% decreased risk for light drinkers (<30 g/d of alcohol), but no association for heavy drinkers (≥30 g/d of alcohol). (Itoh et al. 2001
) In contrast, our findings are consistent with those from a prospective study of 531 men, based on data from the Baltimore Longitudinal Study of Aging (BLSA), which found no association between moderate alcohol use and hearing loss assessed by audiometry. (Brant et al. 1996
Our findings suggest that the relation between alcohol, specifically liquor, and hearing loss may vary by level of vitamin B12 intake. A previous study in this cohort examined the relation between vitamin B12 intake and risk of hearing loss. (Shargorodsky et al. 2010
) We found a lower risk of hearing loss among men with higher intake of vitamin B12 only among those with the highest alcohol consumption, suggesting an interaction between alcohol and vitamin B12 intake. The present study examined the association between alcohol consumption and risk of hearing loss and further examined whether the relation varied by vitamin B12 intake. The observation of higher risk among those with both higher alcohol intake and lower intake of vitamin B12 supports the likelihood of an interaction. Due to its impact on cellular metabolism, vascular function, and myelin synthesis, vitamin B12 deficiency has previously been implicated as an important factor in cochlear pathology. (Brant et al. 1996
; Gates et al. 1993
; Hall 1990
; Shemesh et al. 1993
) In a small cross-sectional study, women with hearing loss had lower serum levels of vitamin B12 (Houston et al. 1999
). Possibly, as higher levels of alcohol consumption may lead to a depletion of hepatic vitamin B12 stores, (Halsted et al. 2002
) greater vitamin B12 intake would be required to preserve cochlear functioning in those who consume higher levels of alcohol. Whether liquor in particular alters vitamin B12 metabolism differently than beer or wine has not been examined.
The lack of association between alcohol intake and the risk of hearing loss did not vary by folate intake. A previous investigation by Durga et al demonstrated that folic acid supplementation slowed low-frequency hearing decline in older adults. (Durga et al. 2007
) However, this was limited to individuals with low levels of blood folate in a country without folate supplementation of the food supply. Thus, it is possible that the relation between alcohol intake and hearing loss may be modified by a level of folate intake lower than in our study population.
Our study differs from previous work in several ways. A particular strength is the long-term prospective updated measurement of alcohol consumption over the course of up to 18 years, with updated measurements every four years. In addition, we examined the relation between more finely defined categories of alcohol consumption than used previously. Further, participants in this study were younger than many of those examined in other studies. We also evaluated the intake of specific alcoholic beverages (beer, red wine, white wine, or liquor). Although we observed an increased risk of hearing loss among those who consumed white wine 2–4 times per week, this result is likely spurious as there was no dose response.
This study has limitations. Although the participants in this cohort may not be representative of the adult U.S. population, follow-up rates are high and information provided is reliable. Assessment of hearing loss was based on self-report of professionally diagnosed hearing loss. Standard pure-tone audiometry is considered the gold standard for evaluation of hearing loss, however self-reported hearing loss has been demonstrated to be a reliable assessment. (Sindhusake et al. 2001
) Moreover, participants were specifically asked whether they had been “professionally diagnosed” with hearing loss, a more objective measure than the commonly used single question, “Do you feel you have a hearing loss?” Nonetheless, given the high prevalence of hearing loss in men of this age group, (Agrawal et al. 2008
) there was likely misclassification of outcome. Further, few participants in our cohort reported very high levels of alcohol consumption, thus our ability to examine the potentially detrimental effects of heavy alcohol use was limited. Assessment of alcohol consumption was based on self-report, however the measures of quantity and frequency of alcohol consumption used in this study were previously validated,(Giovannucci et al. 1991
) and any misclassification in our instruments is unlikely to affect the rank order of alcohol consumption. Finally, it has been suggested that the protective role of alcohol may be to diminish or delay the progression of hearing loss once it has occurred, a process this study cannot examine.
We did not have information on lifetime noise exposure in the whole cohort, a common cause of hearing loss. Although noise exposure may increase the vulnerability to hearing loss related to age (Erway et al. 1996
; Gates et al. 2000
; Kujawa and Liberman 2006
) or other causes, (Brown et al. 1981
) it is not known whether the impact of noise is modified by alcohol. Previous studies of alcohol use and hearing loss have not addressed leisure time and occupational noise exposure in detail.
These findings do not support an overall relation between low or moderate alcohol consumption and risk of hearing loss in older men. Additional studies are needed to examine the relation between alcohol intake and hearing loss in women, younger men, and other racial groups. The potential role of vitamin B12 in alcohol-related ototoxicity merits further investigation.