Allostatic load and risk of hearing impairment

What Explains the Link Between Hearing and Vision Impairment and Cognitive Function? Analysis of Mediating Effects in the USA, England and Ireland

OBJECTIVES

Hearing and vision impairments are associated with cognitive decline and dementia risk. Explanations for this include age-related processes impacting on sensory and cognitive function (common cause), or sensory impairments having a direct or indirect impact on cognition via social engagement, depression and physical activity (cascade). We tested whether associations between hearing, vision and episodic memory were mediated by allostatic load, social engagement, depression and physical activity.

METHODS

We used structural equation modelling with cross-sectional data from the USA (n = 4746, aged 50-101), England (n = 4907, aged 50-89) and Ireland (4292, aged 50-80) to model factors related to the common cause (indexed by allostatic load) and the cascade hypothesis with respect to cognitive ability (episodic memory).

RESULTS

Poorer hearing/vision was associated with lower social engagement, depression and sedentary lifestyle. Poor vision was not related to allostatic load, and poor hearing was associated with allostatic load in only one data set, contributing to a common-cause hypothesis. Lower social engagement, depression and a sedentary lifestyle were associated with poorer episodic memory, contributing to the cascade hypothesis. Using effect estimates to calculate the proportion of the total effects mediated by the combined mediator variables, up to two fifths of the relationship between hearing and vision with episodic memory can be explained by the mediators.

CONCLUSIONS

The association between hearing, vision and episodic memory is mediated by allostatic load, social engagement, depression, and physical activity. The finding that social engagement, depression, and physical activity mediate the association between sensory abilities and cognitive function supported the cascade hypotheses. Interventions to improve healthy lifestyle, reduce depression and foster social engagement of older people with sensory impairments are likely to be beneficial in preventing cognitive decline and dementia.

The interrelationships of hearing function, allostatic load, and cognitive function: Evidence among middle-aged and older Chinese adults

OBJECTIVES

We aim to examine the interrelationships of self-reported hearing function, allostatic load (AL), and cognitive function among middle aged and older adults.

METHODS

Our data were collected from two waves of the China Health and Retirement Longitudinal Study (CHARLS) conducted in 2011 and 2015. The participants' hearing function was measured using self-rated subjective hearing function. Allostatic load (AL) was evaluated by measuring 14 biomarkers associated with physiological health, which were derived from blood samples. Cognitive function was assessed using three domains: episodic memory, mental intactness, and global cognition. To examine the relationships between hearing function, AL, and cognitive function, path analysis with structural equation modeling (SEM) methodology was employed.

RESULTS

Among individuals aged 60 and above non-hearing aids users, the hearing function at Time 1 (T1) in 2011 has a significant association with the level of AL at T1 (β = 0.02, p < 0.001), as well as on cognitive function at Time 2 (T2) in 2015 (β = -0.1, p < 0.001). Additionally, the AL related to the hearing function at T1 associates an increased risk of AL at T2 (β = 0.5, p < 0.001), and is significantly associated with a decrease of cognitive function scores at T2 (β = -0.4, p < 0.001). However, no significant relationship was found among individuals aged 45 - 59 with non-hearing aids utilizers. Similar findings were in the domains of epidemic memory and mental intactness for cognitive function.

CONCLUSIONS

There were interrelationships of subjective hearing function, AL, and cognitive function among aged 60 years and above, but not among those aged 45-59 years old. It may provide valuable insights for identifying subclinical thresholds in the physiological systems of individuals at risk of pathology in cognitive function.

Hearing Impairment and Allostatic Load in Older Adults

Importance

Allostatic load, the cumulative strain that results from the chronic stress response, is associated with poor health outcomes. Increased cognitive load and impaired communication associated with hearing loss could potentially be associated with higher allostatic load, but few studies to date have quantified this association.

Objective

To investigate if audiometric hearing loss is associated with allostatic load and evaluate if the association varies by demographic factors.

Design, Setting, Participants

This cross-sectional survey used nationally representative data from the National Health and Nutrition Examination Survey. Audiometric testing was conducted from 2003 to 2004 (ages 20-69 years) and 2009 to 2010 (70 years or older). The study was restricted to participants aged 50 years or older, and the analysis was stratified based on cycle. The data were analyzed between October 2021 and October 2022.

Exposure

A 4-frequency (0.5-4.0 kHz) pure tone average was calculated in the better-hearing ear and modeled continuously and categorically (<25 dB hearing level [dB HL], no hearing loss; 26-40 dB HL, mild hearing loss; ≥41 dB HL, moderate or greater hearing loss).

Main Outcome and Measures

Allostatic load score (ALS) was defined using laboratory measurements of 8 biomarkers (systolic/diastolic blood pressure, body mass index [calculated as weight in kilograms divided by height in meters squared], and total serum and high-density lipoprotein cholesterol, glycohemoglobin, albumin, and C-reactive protein levels). Each biomarker was assigned a point if it was in the highest risk quartile based on statistical distribution and then summed to yield the ALS (range, 0-8). Linear regression models adjusted for demographic and clinical covariates. Sensitivity analysis included using clinical cut points for ALS and subgroup stratification.

Results

In 1412 participants (mean [SD] age, 59.7 [5.9] years; 293 women [51.9%]; 130 [23.0%] Hispanic, 89 [15.8%] non-Hispanic Black, and 318 [55.3%] non-Hispanic White individuals), a modest association was suggested between hearing loss and ALS (ages 50-69 years: β = 0.19 [95% CI, 0.02-0.36] per 10 dB HL; 70 years or older: β = 0.10 [95% CI, 0.02-0.18] per 10 dB HL) among non-hearing aid users. Results were not clearly reflected in the sensitivity analysis with clinical cut points for ALS or modeling hearing loss categorically. Sex-based stratifications identified a stronger association among male individuals (men 70 years or older: β = 0.22 [95% CI, 0.12-0.32] per 10 dB HL; women: β = 0.08 [95% CI, -0.04 to 0.20] per 10 dB HL).

Conclusion and Relevance

The study findings did not clearly support an association between hearing loss and ALS. While hearing loss has been shown to be associated with increased risk for numerous health comorbidities, its association with the chronic stress response and allostasis may be less than that of other health conditions.