Abstract
Insulin-like Growth Factor 1 (IGF-1) is associated with cardiovascular disease, itself a risk factor for hearing impairment, and, in animal studies, molecular evidence suggests a role for IGF-1 in hearing function. However, the link between IGF-1 and the occurrence of hearing impairment is untested in population-based studies of humans. A total of 4390 participants aged ≥50 y (mean [SD] age 64.2 [8.0] years at baseline, 55% women) from the English Longitudinal Study of Ageing provided serum levels of IGF-1 in 2008 and again in 2012. Hearing acuity was assessed by an objective hearing test (HearCheck handheld device) in 2014 when the prevalence was 38.2%. In the full cohort, IGF-1 was not associated with subsequent hearing impairment (OR5nmol/L increase; 95% CI: 1.01; 0.94, 1.09). However, this relationship appeared to differ by age (p-value for interaction = 0.03). Thus, in younger participants (aged 50–60 y, n = 1400), IGF-1 was associated with lower odds of hearing impairment (0.86; 0.73, 1.00) after adjustment for a range of potential confounders. Among people ≥60 y (n = 2990) there was a non-significant ‘J’-shaped association. Our observational evidence that higher levels of IGF-1 appeared to confer some protection against hearing impairment in some older adults warrants replication in other prospective cohort studies.
Highlights
Age-related hearing loss is the most common cause of adult auditory deficiency and it is a major cause of disability[1, 2]
We have recently shown that physical stature, which is related to Insulin-like Growth Factor 1 (IGF-1) levels[19, 20], is related to hearing impairment[21], with taller individuals less likely to experience hearing loss, which is consistent with results of two other studies[22, 23]
In people at the lower end of the older-aged spectrum, higher levels of IGF-1 were associated with lower odds of hearing impairment and most in participants free of hearing impairment at baseline, where a moderately high effect size was found
Summary
Age-related hearing loss (presbycusis) is the most common cause of adult auditory deficiency and it is a major cause of disability[1, 2]. Atherosclerosis[10, 11] and selected cardiovascular disease risk factors – smoking[12], diabetes[13], overweight12, 14 – have been associated with hearing impairment both in cross-sectional[11, 13, 14] and longitudinal studies[10, 12]. Despite a strong prima facie case for a link between circulating levels of IGF-1 and hearing impairment, to our knowledge, this relationship has not been examined in a well-characterised, free-living population of humans. This was the purpose of the present study in which we utilised data on repeat measurement of IGF-1 levels and subsequent objectively measured hearing impairment in the English Longitudinal Study of Ageing (ELSA)[24]
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