Hearing Loss Emerges As A Key Early Warning Sign For Alzheimer Disease

Even mild proceeding nonaccomplishment predicted accelerated encephalon changes and accrued dementia risk, pinch nan strongest effects seen successful genetically susceptible adults.

Study: Hearing Loss, Brain Structure, Cognition, and Dementia Risk successful nan Framingham Heart Study. Image Credit: Alphavector / Shutterstock

In a caller study published successful nan journal JAMA Network Open, researchers investigated associations betwixt proceeding nonaccomplishment and cognitive function, encephalon building changes, and dementia.

Age-related proceeding nonaccomplishment has go progressively prevalent arsenic nan organization ages worldwide, and it whitethorn beryllium a modifiable consequence facet for dementia and cognitive decline. 

The world prevalence of proceeding loss ranges betwixt 29 percent and 47 percent successful group aged 65 years and older. 

Several studies person recovered associations betwixt proceeding nonaccomplishment and poorer cognitive function, while others person linked it to smaller encephalon volumes aliases nan consequence of dementia.

Framingham Heart Study Used to Evaluate Brain and Cognitive Outcomes

In nan coming study, researchers investigated nan associations of proceeding nonaccomplishment pinch a wide scope of brain-related outcomes and incident dementia.

The squad utilized information from nan Framingham Heart Study (FHS), a three-generational, prospective cohort study. The FHS offspring study cohort (second generation) enrolled 5,124 individuals successful 1971 who were studied erstwhile each 4 years complete 10 cycles.

Two partially overlapping samples were derived from participants who completed nan sixth rhythm (1995 to 1998) and a proceeding assessment. 

Sample 1 included participants who underwent cognitive appraisal and encephalon magnetic resonance imaging (MRI) astatine nan seventh and eighth introspection cycles.

Sample 2 comprised group aged 60 years aliases older who were followed up for incident dementia analysis.

Detailed Hearing Assessments and Audiometry-Based Classifications

A questionnaire was administered to cod accusation connected subjective proceeding loss, caput injury, otosclerosis, tinnitus, Ménière disease, dizzy spells, family history of proceeding loss, usage of ototoxic medications, sound exposure, and usage of proceeding aids. An audiologist performed axenic reside period testing.

Hearing nonaccomplishment was separately analyzed for each receptor utilizing pure-tone averages (PTAs) astatine 0.5, 1, 2, and 4 kHz.

Neuropsychological Testing and MRI Measures of Brain Structure

Cognitive capacity and diminution were assessed utilizing a artillery of validated neuropsychological tests. T1-weighted encephalon MRI images were obtained, and nan pursuing measures were quantified: hippocampal measurement (HPV), full cerebral encephalon measurement (TCBV), and achromatic matter hyperintensity measurement (WMHV). Changes successful these measures from nan seventh to nan eighth introspection cycles were calculated.

Statistical Models Evaluating Dementia Risk and Brain Changes

Incidence of all-cause and Alzheimer's dementia was examined successful sample 2. Multivariable linear regressions were performed to measure associations of PTA and proceeding nonaccomplishment categories (no, slight, mild, aliases astatine slightest mean proceeding loss) pinch neuropsychological measures, TCBV, WMHV, and HPV, adjusting for age, sex, education, caput size, and nan clip betwixt proceeding appraisal and neuropsychological information aliases baseline MRI.

The longitudinal associations of PTA and proceeding nonaccomplishment categories pinch incident all-cause and Alzheimer's dementia were assessed utilizing Cox proportional hazards regressions, adjusted for age, education, sex, and apolipoprotein E (APOE) ε4 bearer status.

Additional analyses adjusted for manner and vascular covariates, including type 2 diabetes, systolic humor pressure, and smoking status. 

The authors besides examined whether adding proceeding nonaccomplishment to a baseline dementia consequence exemplary modestly improved prediction accuracy.

Hearing Loss Associated With WMH Progression and Executive Decline

Sample 1 for MRI and cognitive analyses included 1,656 participants (mean property 58.1 years). Sample 2 comprised 935 individuals (mean property 67.6 years). Males had greater proceeding nonaccomplishment than females, and nan proportionality pinch normal proceeding decreased pinch age.

The squad recovered a linear relation betwixt higher PTA thresholds and greater increases successful WMHV, arsenic good arsenic greater declines successful executive function. In contrast, representation and world cognition showed nary important associations pinch proceeding loss.

WMHV accrued much successful group pinch astatine slightest flimsy proceeding nonaccomplishment than successful those pinch normal hearing. Individuals pinch astatine slightest mild proceeding nonaccomplishment had a smaller TCBV astatine baseline and a greater diminution successful executive function. Adjustment for vascular and manner factors did not change these results. 

Subjective proceeding nonaccomplishment was besides associated pinch poorer executive usability and higher WMHV, moreover erstwhile audiometry did not bespeak mean aliases worse proceeding loss, suggesting that self-report provides complementary information.

Dementia Risk Elevated successful Individuals With Even Slight Hearing Loss

During 15 15-year follow-up, 12.7 percent of sample 2 developed dementia (77 percent Alzheimer's dementia). Individuals pinch astatine slightest flimsy proceeding nonaccomplishment had a importantly higher consequence of dementia than those pinch normal proceeding (hazard ratio 1.71, CI 1.01–2.90).

The consequence of dementia was importantly greater among APOE ε4 carriers pinch mild proceeding nonaccomplishment than among those pinch normal hearing, suggesting a gene-environment interaction. Subjective proceeding nonaccomplishment was besides associated pinch higher dementia consequence successful ε4 carriers. 

Participants pinch astatine slightest flimsy proceeding nonaccomplishment who did not usage proceeding immunodeficiency had a higher dementia risk, whereas proceeding assistance users showed a smaller and nonsignificant increase. 

Exploratory activity analyses showed little TCBV successful men and faster WMHV progression successful women. Adding proceeding nonaccomplishment to dementia prediction models modestly improved consequence favoritism metrics specified arsenic nett reclassification scale and integrated favoritism index.

Hearing Loss arsenic a Potential Marker of Dementia Susceptibility

Taken together, nonsubjective proceeding nonaccomplishment was associated pinch a important summation successful dementia risk, pinch categorical analyses showing a 71 percent higher consequence for individuals pinch astatine slightest flimsy proceeding loss.

Dementia consequence was notably higher among APOE ε4 carriers pinch proceeding nonaccomplishment than among those pinch normal hearing. Hearing nonaccomplishment was associated pinch accelerated executive decline, little encephalon volume, and faster accumulation of achromatic matter abnormalities, but not pinch representation aliases world cognition declines.

The findings propose that proceeding testing whitethorn thief place individuals astatine accrued consequence of dementia. However, nan APOE ε4 relationship requires replication owed to mini subgroup sizes and humble estimate precision.

Overall, proceeding nonaccomplishment should beryllium viewed arsenic a imaginable marker of accrued dementia susceptibility, alternatively than grounds of causation, fixed nan observational design, aggregate comparisons, and imaging differences crossed study waves.