The amount of attention to age-related hearing loss (ARHL) has been growing, not only from the perspective of being one of the most common health conditions affecting older adults, but also from the perspective of its relation to cognition. Results from a number of epidemiological and laboratory studies have demonstrated a significant link between ARHL and cognitive decline. The Lancet International Commission on Dementia, Prevention, Intervention, and Care has estimated that mid-life hearing loss, if eliminated, might decrease the risk of dementia by nine percent, since hearing loss is a modifiable age-associated condition linked to dementia. Despite numerous research efforts, elucidation of the underlying causal relationships between auditory and cognitive decline has not yet reached a consensus. In this review article, we focused on the hypotheses of etiological mechanisms between ARHL and cognitive decline: (1) cognitive load hypothesis; (2) common cause hypothesis; (3) cascade hypothesis; and (4) overdiagnosis or harbinger hypothesis. Factual evidence obtained in previous studies was assessed to understand the link between ARHL and cognitive decline or dementia. Additionally, an overview of the conceivable effects of hearing intervention, e.g., hearing aids and cochlear implants, on cognition were presented, and the role of hearing aid use was considered for the relevant hypotheses. We should continue to strive for social enlightenment towards the importance of 'hearing well', and cultivate a necessity for hearing screening among patients at risk of cognitive decline.

Background: The gait speed and handgrip strength represented the core determinants of physical frailty and sarcopenia, which were reported to be associated with cognitive impairment and decline. Different physical measures might differentially affect cognitive changes, such as higher-level cognitive change and global cognitive decline. This study examined the differential associations of gait speed and handgrip strength with 10-year cognitive changes among community-dwelling older people. Methods: Participants aged 60 years and over living in the community were invited for study. Gait speed and handgrip strength were classified into 5 groups based on quintiles at baseline. Cognitive functions were assessed using the Mini-Mental State Examination (MMSE) and Digit Symbol Substitution Test (DSST) every 2 years from baseline for a period of 10 years. Linear mixed effects models were used to determine the role of gait speed and handgrip strength in the prediction of 10-year cognitive changes by adjusting covariates, including age, gender, education, depressive symptoms, marital status, smoking status, instrumental activities of daily life (IADL), Charlson Comorbidity Index (CCI), and body mass index (BMI) at baseline. Results: A total of 1096 participants were enrolled in the study. The mean age was 69.4 ± 5.8 years and 50.9% were male. The slowest gait speed group showed a significantly greater decline in the DSST scores over 10 years than the highest group (estimate = 0.28 and P = 0.003), but not in the MMSE scores (estimate = 0.05 and P = 0.078). The lowest handgrip strength group showed a significantly greater decline in the MMSE scores than the highest group (estimate = 0.06 and P = 0.039) and in the DSST scores than the highest two quintiles (estimate = 0.20 and P = 0.033 for the fourth quintile; estimate = 0.20 and P = 0.040 for the highest quintile) over 10-year follow-up. Conclusions: A slow gait speed could predict 10-year cognitive decline using DSST, and a low handgrip strength could predict 10-year cognitive decline using MMSE in addition to DSST. Thus both physical measures are lined to cognitive decline but there may be different mechanisms between brain and physical functions.

No abstract

Daily intake of various kinds of food might be a protective factor against cognitive decline in community-dwelling Japanese older adults. Geriatr Gerontol Int 2017; 17: 937-944.

Data were derived from the National Institute for Longevity Sciences-Longitudinal Study of Aging. Subjects comprised 403 men and 373 women aged 60-81 years at baseline who participated in the follow-up study at least once. Bean, soy product and soy isoflavone intake was assessed using a 3-day dietary record at baseline. Cognitive function was assessed by the Mini-Mental State Examination (MMSE). MMSE scores of ≤23 were used to define cognitive impairment. The relationship between bean, soy product and soy isoflavone intake and cognitive impairment was assessed using a generalized estimating equation. Multivariate-adjusted odds ratios (95% confidence intervals) for cognitive impairment with a 1 s.d. increase in total bean, total soybean and total soy isoflavone intakes were 0.48 (0.28-0.81; p = 0.006), 0.51 (0.32-0.83; p = 0.007), and 0.55 (0.32-0.93; p = 0.026), respectively, in women. Total soybean and soy isoflavone intake might decrease the risk of cognitive impairment in elderly Japanese women.

A growing body of literature has demonstrated that dementia and hearing loss are interrelated. Recent interest in dementia research has expanded to brain imaging analyses with auditory function. The aim of this study was to investigate the link between hearing ability, which was assessed using pure-tone audiometry, and the volume of brain regions, specifically the hippocampus, entorhinal cortex, Heschl’s gyrus, and total gray matter, using Freesurfer software and T1-weighted brain magnetic resonance imaging. The data for 2082 samples (age range = 40–89 years) were extracted from a population-based cohort of community dwellers. Hearing-impaired individuals showed significantly smaller hippocampal volumes compared with their non-hearing-impaired counterparts for all auditory frequency ranges. In addition, a correlational analysis showed a significant dose-response relationship for hearing ability and hippocampal volume after adjusting for potential confounding factors so that the more degraded the peripheral hearing was, the smaller the hippocampal volume was. This association was consistent through the auditory frequency range. The volume of the entorhinal cortex, right Heschl’s gyrus and total gray matter did not correlate with hearing level at any frequency. The volume of the left Heschl’s gyrus showed a significant relationship with the hearing levels for some auditory frequencies. The current results suggested that the presence of hearing loss after middle age could be a modifier of hippocampal atrophy.

During the last three decades, Japan has become one of the world's top countries for longevity, and the increase in average life expectancy is accompanied by a sharp rise in older population 65 years of age and above to *28%. This study aimed to examine the changes in major health-related measures, including a physical constitution, physical function, and functional capacity of community-dwelling Japanese older people in the last decade. From the data of 13 longitudinal cohort studies on aging conducted in Japan with a total of 13,441 older subjects, this study analyzed the changes in six indices that are related to health and functioning of the older people; height, weight, body mass index, walking speed, grip strength, and instrumental activity of daily living, between 2007 (-2 years) and 2017 (-2 years). Comparison of data for the two periods between subjects matched for age group and gender evidently showed better health status and a slower decline in most of the health-related measures in 2017 compared to a decade ago. The results of this study indicate that the phenomenon of ''rejuvenation'' is occurring among the new generation of Japanese older adults, and the importance of this older population as a social resource in the super-aged society should be reacknowledged.

We examined associations between dietary diversity and all-cause and cause-specific mortality in 386 men and 413 women (age range, 60–79 years at baseline) who took part in the National Institute for Longevity Sciences-Longitudinal Study of Aging study from 1997 to 2000. Dietary intake was assessed using three-day dietary records and photographs. The Quantitative Index for Dietary Diversity was used to determine the dietary diversity among thirteen food groups. Dietary diversity score and each food intake were examined by sex-stratified tertiles, and hazard ratios (HR) were calculated to compare the risk for all-cause and cause-specific deaths across tertiles, after controlling for age, sex, body mass index, alcohol intake, smoking status, education, physical activity, and disease history. During a mean follow-up of 15.7 years, 289 subjects (36.2%) died. Compared to the subjects in the lowest tertile, the multivariate-adjusted HR for all-cause and cancer mortality was 0.69 (95% confidence interval (CI): 0.51–0.94) and 0.57 (95% CI: 0.33–0.98), respectively (trend p < 0.05), in subjects in the highest tertile of dietary diversity. There were no significant associations between dietary diversity score and death from cardiovascular or cerebrovascular disease. Eating a variety of foods might contribute to longevity in older Japanese community dwellers.