Publications

The Alzheimer's Disease Neuroimaging Initiative (ADNI) is a large multi-center study designed to develop optimized methods for acquiring longitudinal neuroimaging, cognitive, and biomarker measures of AD progression in a large cohort of patients with Alzheimer's disease (AD), patients with Mild Cognitive Impairment, and healthy controls. Detailed neuropsychological testing was conducted on all participants. We examined the factor structure of the ADNI Neuropsychological Battery across older adults with differing levels of clinical AD severity based on the Clinical Dementia Rating Scale (CDR). Confirmatory factor analysis (CFA) of 23 variables from 10 neuropsychological tests resulted in five factors (memory, language, visuospatial functioning, attention, and executive function/processing speed) that were invariant across levels of cognitive impairment. Thus, these five factors can be used as indicators of cognitive function in older adults who are participants in ADNI.

BACKGROUND

Previous studies have suggested that hearing loss, which is highly prevalent but undertreated in older adults, may be associated with gait and physical functioning. Determining if hearing loss is independently associated with gait speed is critical toward understanding whether hearing rehabilitative interventions could help mitigate declines in physical functioning in older adults.

METHODS

We analyzed cross-sectional data from the 1999 to 2002 cycles of the National Health and Nutritional Examination Survey during which participants 50-69 years (n=1180) underwent hearing and gait speed assessments. Hearing was defined by a pure tone average of hearing thresholds at 0.5-4kHz tones in the better-hearing ear. Gait speed was obtained in a timed 20-ft (6.1m) walk. Linear and logistic regression models were used to examine the association between hearing loss and gait speed while adjusting for demographic and cardiovascular risk factors. Analyses incorporated sampling weights to yield results generalizable to the U.S. population.

RESULTS

In a model adjusted for demographic and cardiovascular risk factors, a hearing loss was associated with slower gait speed (-0.05m/s per 25dB of hearing loss [95% CI: -0.09 to -0.02]) and an increased odds of having a gait speed <1.0m/s (OR=2.0 per 25dB of hearing loss, 95% CI: 1.2-3.3). The reduction in gait speed associated with a 25dB hearing loss was equivalent to that associated with an age difference of approximately 12 years.

CONCLUSIONS

Greater hearing loss is independently associated with slower gait speed. Further studies investigating the mechanistic basis of this association and whether hearing rehabilitative interventions could affect gait and physical functioning are needed.