Age‐Related Sensory Impairments and Risk of Cognitive Impairment

Abstract

Background/Objectives To evaluate the associations of sensory impairments with the 10-year risk of cognitive impairment. Previous work has primarily focused on the relationship between a single sensory system and cognition. Design The Epidemiology of Hearing Loss Study (EHLS) is a longitudinal, population-based study of aging in the Beaver Dam, WI community. Baseline examinations were conducted in 1993 and follow-up exams have been conducted every 5 years. Setting General community Participants EHLS members without cognitive impairment at EHLS-2 (1998–2000). There were 1,884 participants (mean age = 66.7 years) with complete EHLS-2 sensory data and follow-up information. Measurements Cognitive impairment was a Mini-Mental State Examination score of < 24 or history of dementia or Alzheimer’s disease. Hearing impairment was a pure-tone average of hearing thresholds (0.5, 1, 2 and 4 kHz) of > 25 decibel Hearing Level in either ear. Visual impairment was Pelli-Robson contrast sensitivity of < 1.55 log units in the better eye and olfactory impairment was a San Diego Odor Identification Test score of < 6. Results Hearing, visual, and olfactory impairment were independently associated with cognitive impairment risk [Hearing: Hazard Ratio (HR) = 1.90, 95% Confidence Interval (C.I.) = 1.11, 3.26; Vision: HR = 2.05, 95% C.I. = 1.24, 3.38; Olfaction: HR = 3.92, 95% C.I. = 2.45, 6.26]. However, 85% with hearing impairment, 81% with visual impairment, and 76% with olfactory impairment did not develop cognitive impairment during follow-up. Conclusion The relationship between sensory impairment and cognitive impairment was not unique to one sensory system suggesting sensorineural health may be a marker of brain aging. The development of a combined sensorineurocognitive measure may be useful in uncovering mechanisms of healthy brain aging.

APOE-ɛ4 effects on longitudinal decline in olfactory and non-olfactory cognitive abilities in middle-aged and old adults

“…These non-olfactory associations indicate that cognitive decline tend to covary across different domains, as has been discussed within the “common-cause” framework of cognitive aging 47 .…”

Predictive value of olfactory impairment for cognitive decline among cognitively normal adults

“…The final study utilized the San Diego Odor Identification Test (SDOIT), an 8‐item evaluation wherein respondents identify scents on a photo array in two trials . Olfactory impairment was defined as binary based on published validation of scores.…”

“…Finally, at 10 years of follow‐up, the odds of cognitive decline were calculated as 6.41 (95% CI 4.68–8.77) among those with olfactory impairment compared to normosmics at baseline (Fig. ) …”

“…Finally, other sensory impairments (hearing, vision) were also reported to independently predict incident cognitive decline. Indeed, prediction improved when all three impairments were considered together so that an individual with impairments in all three senses was at 15 times greater risk compared with an individual without baseline sensory impairment …”

“…However, this study included only two longitudinal cohort studies, precluding strong conclusions about the predictive utility of olfactory impairment . Several longitudinal studies have been published since 2012 that support the predictive value of olfactory testing in future cognitive decline …”