Hearing loss and cardiovascular disease (CVD) are hallmark characteristics of aging in the United States. Hearing loss may affect as many as one in five adults or about 29 million people in the country,1 while CVD affects over 92 million adults—and this is expected to increase to over 43 percent of the U.S. adult population by 2030.2 Hearing loss significantly affects people's quality of life,3,4 and, especially in older adults, it is associated with withdrawal from social interactions,5 which may lead to loneliness,6,7 anxiety, and depression.8,9 CVD, in turn, is a well-known consequence of both acute and chronic psychological stress.10-12 Hearing loss is also associated with CVD,13-16 specifically in terms of cochlear function.17 However, the precise nature and degree of the relationship between hearing problems, psychological distress, and CVD are still unclear.18,19 In this study, we investigated the possibility that hearing loss and CVD may be related in part through their common relationship with psychological distress. If these conditions are in fact mediated through psychological distress, health care professionals would have a stronger motivation to address psychosocial factors in the clinical management of hearing loss,20 especially in individuals already living with, or at risk for, CVD.
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iStock/ Mongkolchon Akesin, heart health, cardiovascular health, hearing loss.
THE DATA
We used data from the 1997-2017 National Health Interview Survey (NHIS), a multipurpose survey conducted annually by the U.S. Census Bureau for the National Center for Health Statistics of the Centers for Disease Control and Prevention (CDC).21 We pooled data from 1997 to 2017, and included only those from adults aged 18 years and above who provided full information on all analysis variables. A total of 623,416 samples were included.
As our measure of self-reported hearing problems, we used responses to the question: “Without the use of hearing aids or other listening devices, is your hearing (a) excellent, (b) good, (c) a little trouble hearing, (d) moderate trouble, (e) a lot of trouble, or (f) are you deaf?” From the responses, we constructed a three-category variable grouping: (1) excellent or good, (2) a little/moderate trouble, and (3) a lot of trouble/deaf. We kept the groups large to have more participants in each group and simplify the statistical analysis.
As our measure of cardiovascular disease, we used responses to survey questions that asked participants if they had been told by a doctor or other health professionals that they have a CVD, including (1) stroke, (2) angina pectoris, (3) hypertension, (4) heart attack (myocardial infarction), (5) coronary heart disease, or (6) other heart conditions/diseases. The last category included heart failure, any chronic heart condition, rheumatic heart disease, atrial or mitral valve disease or damage, or any kind of heart condition or disease other than coronary heart disease, angina pectoris, or a heart attack.
As our measure of psychological distress, we used responses to the Kessler 6 Scale (K6),22 which consists of six questions that measure nonspecific psychological distress in the past 30 days. We analyzed the results in two ways: one in which this variable was treated as a yes/no measure (i.e., respondents did or did not have psychological distress according to the scale's established criteria) and another in which it was treated as a continuous variable consisting of the raw score. Both approaches gave substantially similar results, suggesting that these findings are robust. We also included standard control variables of age, sex, race/ethnicity, marital status, education level, and self-rated health. These control variables have been shown in previous studies to affect risk factors for CVD,23-25 but they were not the variables of primary interest in this study. Thus, we used statistical methods to remove their effects from the final analysis. All estimates were population-weighted, and standard errors were adjusted for the complex survey design as is typically done in this type of research.
ANALYSIS & RESULTS
For our analysis, we used generalized structural equation modeling,26 a statistical method to evaluate the relationship between variables that are actually measured (e.g., degree of self-reported hearing problems) and latent constructs (e.g., CVD) that may not be directly observable in the dataset. A particularly useful characteristic of this method is that it can be visualized through a diagram of a structural model that displays the relationship between variables and constructs.
To draw valid conclusions, we had to initially establish that our data conformed to the four criteria established by Baron and Kenny27 for identifying a mediating relationship, specifically that: (1) hearing problems were significantly associated with CVD; (2) hearing problems were significantly associated with psychological distress; (3) psychological distress was significantly associated with CVD; and (4) the relationship between hearing problems and CVD was attenuated with the inclusion of psychological distress. This means that (1) people reporting a greater degree of hearing problems were more likely to also have CVD; (2) people reporting a greater degree of hearing problems tended to also report having a greater degree of psychological distress; (3) people reporting a greater degree of psychological distress were more likely to have CVD; and (4) when we included psychological distress in the relationship between hearing problems and CVD, we no longer saw as strong a relationship between them than there was without psychological distress in the model, though the relationship remained significant. These results therefore suggest that the relationship between self-reported hearing problems and CVD can be better explained if we include a mediating role for psychological distress in the model. In other words, part of the relationship between hearing problems and CVD can be explained in terms of the existence of a relationship between hearing problems and psychological distress and between psychological distress and CVD.
Through this analysis, we were able to calculate both the direct and indirect effects of self-reported hearing problems on CVD. The direct effect is the degree to which hearing problems predict the presence of CVD in our model directly, while the indirect effect is the degree to which CVD is predicted by the effect of self-reported hearing problems on psychological distress and the effect of psychological distress on CVD. To calculate the indirect effect, we multiplied the effects of hearing problems on psychological distress by the effects of psychological distress on CVD. The total effect was then computed as the sum of the direct and indirect effects of hearing problems on CVD, and the mediating effect was calculated as the proportion of the total effect contributed by the indirect effect. When psychological distress was treated as a continuous variable, the mediating effect was nearly 10 percent, suggesting that about 10 percent of the variance in the relationship between hearing problems and CVD was mediated by individual Kessler 6 scores. When psychological distress was instead treated as a binary variable, meaning each participant was coded as either having or not having psychological distress, the mediating effect was over 30 percent. Thus, we concluded that psychological distress likely contributes to about 10 to 30 percent of the relationship between self-reported hearing problems and CVD.
LIMITATIONS & RECOMMENDATIONS
The study has several limitations. First, it was cross-sectional, meaning that we could not determine the direction of the causal relationships among reported hearing problems, psychological distress, and CVD. That is, we cannot tell from these results whether it is more likely that hearing problems lead to psychological distress, which in turn leads to CVD (as we have proposed), or whether people with CVD-related psychological distress are more likely to report hearing problems. Indeed, some studies have suggested that CVD may lead to hearing impairment or at least a sense of hearing loss by increasing psychosocial stress,28,29 which is in turn linked to a higher incidence of reported hearing problems.30,31 Moreover, many studies have shown that hearing impairment may be caused by a cardiovascular disturbance or disease,32-34 for example, as a result of an inflammatory disease35 or poor vascularization of the inner ear.32, 36-38 Further epidemiological research, especially longitudinal research, is necessary to disentangle the various possible causal pathways linking CVD, hearing loss, and psychological distress.
A second limitation is that we used self-reported degree of hearing problems, not objectively measured hearing impairment (i.e., via audiogram), as our measure of hearing loss. While subjective measures may be preferable when considering how patients react to or cope with their impairment,39,40 there are also known discrepancies between self-assessed and audiometrically assessed hearing loss.41 Therefore, future research on the relationship between hearing loss and CVD should include both objective and subjective measures of hearing.
Finally, the NHIS sampling methods only included adults who do not live in institutions (i.e., retirement homes, long-term care facilities). These populations tend to be older, sicker, and more medically complex than the community-dwelling adults we studied, indicating that our results may not extend to them.
Our study found that psychological distress plays a mediating role in the relationship between CVD and self-reported hearing problems. This finding adds weight to the idea that treatment of hearing loss should also address the communication-related stress imposed by the impairment20 and other factors that affect overall quality of life,42 including the social consequences of living with hearing loss in a hearing world.43 Further research is needed to better determine the direction of causality and identify possible physiological and/or psychosocial bases for this mediating relationship. We also recommend conducting interventional and observational studies of possible benefits of amplification and other strategies and therapies for mitigating hearing loss-related psychological stress44-46 since these may also improve the cardiovascular health of people with hearing impairment.
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