Cognitive status in the oldest old and centenarians: a condition crucial for quality of life methodologically difficult to assess

Measuring Multidimensional Aspects of Health in the Oldest Old Using the NIH Toolbox: Results From the ARMADA Study

OBJECTIVE

The percentage of older adults living into their 80s and beyond is expanding rapidly. Characterization of typical cognitive performance in this population is complicated by a dearth of normative data for the oldest old. Additionally, little attention has been paid to other aspects of health, such as motor, sensory, and emotional functioning, that may interact with cognitive changes to predict quality of life and well-being. The current study used the NIH Toolbox (NIHTB) to determine age group differences between persons aged 65-84 and 85+ with normal cognition.

METHOD

Participants were recruited in two age bands (i.e., 65-84 and 85+). All participants completed the NIHTB Cognition, Motor, Sensation, and Emotion modules. Independent-samples t-tests determined age group differences with post-hoc adjustments using Bonferroni corrections. All subtest and composite scores were then regressed on age and other demographic covariates.

RESULTS

The 65-84 group obtained significantly higher scores than the 85+ group across all cognitive measures except oral reading, all motor measures except gait speed, and all sensation measures except pain interference. Age remained a significant predictor after controlling for covariates. Age was not significantly associated with differences in emotion scores.

CONCLUSIONS

Results support the use of the NIHTB in persons over 85 with normal cognition. As expected, fluid reasoning abilities and certain motor and sensory functions decreased with age in the oldest old. Inclusion of motor and sensation batteries is warranted when studying trajectories of aging in the oldest old to allow for multidimensional characterization of health.

The relationship between depressive mood and subjective health in centenarians and near-centenarians: a cross-sectional study from Korean centenarian cohort

BACKGROUND

With the rapid increase in population longevity, more clinical attention is being paid to the overall health of long-lived people, especially centenarians. Subjective health, which is the perception of one's health status, predicts both mortality and declining physical function in older adults. The purpose of this study was to investigate the factors related to subjective health among centenarians and near-centenarians (ages ≥95) living in a rural area of South Korea.

METHODS

A total of 101 participants were enrolled from four different regions (Gurye, Gokseong, Sunchang, and Damyang), known as the Longevity Belt in Korea. Variables assessing physical and mental health, including the results of blood tests, were examined. Factors associated with good subjective health were identified with logistic regression analysis.

RESULTS

Fifty-six participants (59.6%) were subjectively healthy among the centenarians and near-centenarians. Logistic regression analysis revealed that depressive mood was the only factor associated with subjective health and was negatively correlated. The regression model explained 39% of the variance in subjective health.

CONCLUSIONS

These findings emphasize the importance of mental health at very advanced ages. Because depressive mood negatively correlates with subjective health, more attention is needed to prevent and manage mood symptoms of people of advanced ages, including centenarians.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Geriatric syndromes in a centenarians population

Background

Centenarians develop diseases later than younger populations.

Aims

Assessment of geriatric syndromes in centenarians living in Marseille in 2020.

Methods

Observational preliminary study describing centenarians living in the Marseille area, being part of the patients base of the general practitioners (GPs).

Results

Twenty-two centenarians were enrolled, including seventeen women (77.3%). Thirteen centenarians lived in nursing homes (NH) and nine in private housing (PH). All were dependent for daily living activities and 78.9% used walkers to get around. GPs consultations were exclusively home visits (in NH or PH). Centenarians living in NH presented more cognitive impairments, more comorbidities, and fewer hospitalizations during the past year compared to centenarians living in PH.

Discussion

Although centenarians represent a model of successful aging for society, all were dependent and had at least one geriatric syndrome.

Conclusions

Maintaining centenarians at home requires technical aids and intervention of several professional caregivers relying on family support.

Biological Frailty Index in centenarians

This study measured the subclinical frailty of centenarians by looking at the accumulation of their biological abnormalities. For this aim, a biological Frailty Index (FI) was computed in centenarians living in Northern Italy. The median value of the biological FI was 0.33 (interquartile range, IQR 0.28–0.41). The biological FI did not significantly differ between women (0.34, IQR 0.31–0.39) and men (0.32, IQR 0.26–0.43). The biological FI seems to have a narrower distribution compared to clinical FI we previously computed in the same cohort. In conclusion, our study suggests that centenarians benefit from exceptional biological reserves that might be underestimated by clinical appearances.

Association of rs3027178 polymorphism in the circadian clock gene PER1 with susceptibility to Alzheimer's disease and longevity in an Italian population

Many physiological processes in the human body follow a 24-h circadian rhythm controlled by the circadian clock system. Light, sensed by retina, is the predominant “zeitgeber” able to synchronize the circadian rhythms to the light-dark cycles. Circadian rhythm dysfunction and sleep disorders have been associated with aging and neurodegenerative diseases including mild cognitive impairment (MCI) and Alzheimer’s disease (AD). In the present study, we aimed at investigating the genetic variability of clock genes in AD patients compared to healthy controls from Italy. We also included a group of Italian centenarians, considered as super-controls in association studies given their extreme phenotype of successful aging. We analyzed the exon sequences of eighty-four genes related to circadian rhythms, and the most significant variants identified in this first discovery phase were further assessed in a larger independent cohort of AD patients by matrix assisted laser desorption/ionization-time of flight mass spectrometry. The results identified a significant association between the rs3027178 polymorphism in the PER1 circadian gene with AD, the G allele being protective for AD. Interestingly, rs3027178 showed similar genotypic frequencies among AD patients and centenarians. These results collectively underline the relevance of circadian dysfunction in the predisposition to AD and contribute to the discussion on the role of the relationship between the genetics of age-related diseases and of longevity.

No association between frailty index and epigenetic clocks in Italian semi-supercentenarians

Centenarians experience successful ageing, although they still present high heterogeneity in their health status. The frailty index is a biomarker of biological age, able to capture such heterogeneity, even at extreme old age. At the same time, other biomarkers (e.g., epigenetic clocks) may be informative the biological age of the individual and potentially describe the ageing status in centenarians. In this article, we explore the relationship between epigenetic clocks and frailty index in a cohort of Italian centenarians. No association was reported, suggesting that these two approaches may describe different aspects of the same ageing process.

Development of a self-assessment behavioral and psychological symptoms of dementia competency scale for care teams at long-term geriatric care facilities

Understanding the behavioral and psychological symptoms of dementia (BPSD) is important for caregivers in long-term geriatric care facilities. In this study performed in 43 long-term care facilities, we evaluated the ability of caregivers to recognize BPSD through the development and validation of self-assessment scales. Reliability and validity of the scales were determined using Cronbach's alpha coefficient, the test/retest method, exploratory factor analysis, confirmatory factor analysis, criteria-related validity, and construct validity. We analyzed cross-sectional data from 310 participants. Factor analysis showed a positive correlation for all scale items (r_s = .43-.73). Significant correlations arose from the test/retest method (r_s = .48-.76). The α coefficient of all items except one was .70 or more, indicating sufficient reliability. Criteria-related validity (r_s = .43-.73) and construct validity (r_s = .13-.52) revealed a positive correlation. The BPSD Team Care Self-Assessment Scale is reliable and could ensure BPSD competency in caregivers.

A geroscience approach for Parkinson's disease: Conceptual framework and design of PROPAG-AGEING project

Advanced age is the major risk factor for idiopathic Parkinson's disease (PD), but to date the biological relationship between PD and ageing remains elusive. Here we describe the rationale and the design of the H2020 funded project "PROPAG-AGEING", whose aim is to characterize the contribution of the ageing process to PD development. We summarize current evidences that support the existence of a continuum between ageing and PD and justify the use of a Geroscience approach to study PD. We focus in particular on the role of inflammaging, the chronic, low-grade inflammation characteristic of elderly physiology, which can propagate and transmit both locally and systemically. We then describe PROPAG-AGEING design, which is based on the multi-omic characterization of peripheral samples from clinically characterized drug-naïve and advanced PD, PD discordant twins, healthy controls and "super-controls", i.e. centenarians, who never showed clinical signs of motor disability, and their offspring. Omic results are then validated in a large number of samples, including in vitro models of dopaminergic neurons and healthy siblings of PD patients, who are at higher risk of developing PD, with the final aim of identifying the molecular perturbations that can deviate the trajectories of healthy ageing towards PD development.

Studying the Interplay Between Apolipoprotein E and Education on Cognitive Decline in Centenarians Using Bayesian Beta Regression

Apolipoprotein E (APOE) is an important risk factor for cognitive decline and Alzheimer's disease in aging individuals. Among the 3 known alleles of this gene: e2, e3, and e4, the e4 allele is associated with faster cognitive decline and increased risk for Alzheimer's and dementia, while the e2 allele has a positive effect on longevity, and possibly on preservation of cognitive function. Education also has an important effect on cognition and longevity but the interplay between APOE and education is not well-characterized. Previous studies of the effect of APOE on cognitive decline often used linear regression with the normality assumption, which may not be appropriate for analyzing bounded and skewed neuropsychological test scores. In this paper, we applied Bayesian beta regression to assess the effect of APOE alleles on cognitive decline in a cohort of centenarians with longitudinal assessment of their cognitive function. The analysis confirmed the negative association between older age and cognition and the beneficial effect of education that persists even at the extreme of human lifespan in carriers of the e3 allele. In addition, the analysis showed an association between APOE and cognition that is modified by education. Surprisingly, an antagonistic interaction existed between higher education and APOE alleles, suggesting that education may reduce the positive effect of APOE e2 and increase the negative effect of APOE e4 at extreme old age.

Cognitive, functional, physical, and nutritional status of the oldest old encountered in primary care: a systematic review

Background

The oldest old (individuals over 90 years) are a fast-growing population. Characterizing their specificity would be helpful to adapt health care. This study aimed to characterize the cognitive, functional, nutritional, and physical status of individuals over 90.

Methods

We conducted a systematic review of cross-sectional or cohort studies of individuals aged 90 years old or more, living at home or in a nursing home, in April 2018. Two reviewers selected eligible articles, extracted data, and evaluated the risk of bias (assessed by the Newcastle-Ottawa Scale).

Results

The search strategy identified 3086 references; 35 articles were included referring to 8 cross-sectional and 27 longitudinal studies. Dementia was diagnosed in 30–42.9% of study participants, cognitive impairment in 12–50%, and 31–65% had no cognitive impairment. In terms of activities of daily living, 14–72.6% of individuals had no difficulty, 35.6–38% had difficulty, and 14.4–55.5% were dependent. For instrumental activities of daily living, 20–67.9% needed help. Regarding nutritional status, the Mini Nutritional Assessment Short Form mean score ranged from 10.3 (SD: 1.8) to 11.1 (SD: 2.4). Eight to 32% of individuals could not stand up from a chair, 19–47% could stand without the use of their arms; and 12.9–15% were not able to walk 4 m.

Conclusions

These results suggest a heterogeneous population with a certain proportion of oldest old with a low level of disability. These findings suggest that a specific approach in the care of the oldest old could help prevent disability.

Analyzing functional status and its correlates in Chinese centenarians: A cross-sectional study

Factors affecting independence in basic and instrumental activities of daily living have been established in older adults, but not centenarians. The purpose of this study was to examine the state and factors affecting activities of daily living independence in centenarians who resided in Guangxi Province, China. A cross-sectional design was used. Activities of daily living, physical activity, mobility, and physical performance were measured by the Population Study of ChINese Elderly study instruments, and demographics and cognition were assessed. Of the 228 participants, 57% were independent in basic activities of daily living and 5.7% in instrumental activities of daily living. Stepwise regression showed physical activity, cognition, calf circumference, and self-reported health were associated with basic activities of daily living. Physical activity, mobility, cognition, and physical performance were correlated with instrumental activities of daily living. In conclusion, the Chinese centenarians showed impaired instrumental activities of daily living but mostly maintained basic functioning. Physical activity and cognition were associated with activities of daily living independence.

Longitudinal Maintenance of Cognitive Health in Centenarians in the 100-plus Study

IMPORTANCE

Some individuals who reach ages beyond 100 years in good cognitive health may be resilient against risk factors associated with cognitive decline. Exploring the processes underlying resilience may contribute to the development of therapeutic strategies that help to maintain cognitive health while aging.

OBJECTIVE

To identify individuals who escape cognitive decline until extreme ages and to investigate the prevalence of associated risk factors.

DESIGN, SETTING, AND PARTICIPANTS

The 100-plus Study is a prospective observational cohort study of community-based Dutch centenarians enrolled between 2013 and 2019 who were visited annually until death or until participation was no longer possible. The centenarians self-reported their cognitive health, as confirmed by a proxy. Of the 1023 centenarians approached for study inclusion, 340 fulfilled the study criteria and were included in analyses. Data analysis was performed from April 2019 to December 2019.

MAIN OUTCOMES AND MEASURES

Cognition was assessed using the Mini-Mental State Examination (MMSE). To identify centenarians who escape cognitive decline, this study investigated the association of baseline cognition with survivorship and cognitive trajectories for at least 2 years of follow-up using linear mixed models, adjusted for sex, age, and education. This study investigated the prevalence of apolipoprotein E (APOE) genotypes and cardiovascular disease as risk factors associated with cognitive decline.

RESULTS

At baseline, the median age of 340 centenarians was 100.5 years (range, 100.0-108.2 years); 245 participants (72.1%) were female. The maximum survival estimate plateaued at 82% per year (95% CI, 77% to 87%) across centenarians who scored 26 to 30 points on the baseline MMSE (hazard ratio, 0.56; 95% CI, 0.42 to 0.75; P < .001), suggesting that an MMSE score of 26 or higher is representative of both cognitive and physical health. Among the 79 centenarians who were followed up for 2 years or longer, those with baseline MMSE score less than 26 experienced a decline in MMSE score of 1.68 points per year (95% CI, -2.45 to -0.92 points per year; P = .02), whereas centenarians with MMSE scores of 26 or higher at baseline experienced a decline of 0.71 point per year (95% CI, -1.08 to -0.35 points per year). For 73% of the centenarians with baseline MMSE scores of 26 or higher, no cognitive changes were observed, which often extended to ensuing years or until death. It is estimated that this group is representative of less than 10% of Dutch centenarians. In this group, 18.6% carried at least 1 APOE-ε4 allele, compared with 5.6% of the centenarians with lower and/or declining cognitive performance.

CONCLUSIONS AND RELEVANCE

Most centenarians who scored 26 or higher on the MMSE at baseline maintained high levels of cognitive performance for at least 2 years, in some cases despite the presence of risk factors associated with cognitive decline. Investigation of this group might reveal the processes underlying resilience against risk factors associated with cognitive decline.

Clinical, functional, mental and social profile of the Nicoya Peninsula centenarians, Costa Rica, 2017

BACKGROUND

In Latin America, knowledge about the demography and health status of adults aged 100 years and over is scarce. Insufficient studies of the elderly population in Costa Rica exist despite having a "Blue Zone" (geographical area with a high concentration of centenarians) in the Peninsula of Nicoya, with a high percentage of centenarians in the districts of Santa Cruz, Nicoya, Hojancha, Nandayure and Carrillo.

AIMS

To describe the clinical, functional, mental and social profile of centenarians residing in the Blue Zone of the Peninsula of Nicoya, Costa Rica.

METHODS

This is a cross-sectional study using a population base of 43 community-dwelling centenarians. A comprehensive geriatric assessment was performed, including sociodemographic information, health status, electrocardiogram and laboratory tests.

RESULTS

The mean age of centenarians was 101.93 years, of whom 18 (42%) were men and 25 (58%) women. Two (4.6%) resided in nursing homes. Women had worse results than men in the evaluation of dependence on basic and instrumental activities of daily living, and the short physical performance battery performance test. A high prevalence of low Vitamin D levels (87.3%), atrial fibrillation (9.3%) and visual impairment (46.5%) was found.

CONCLUSIONS

This is the first study describing the medical, functional, mental and social profile of centenarians in the Peninsula of Nicoya (Blue Zone) in Costa Rica. This population has a high prevalence of malnutrition and hypertension with dependence on the basic activities of daily living, and a low prevalence for diabetes, depression, ischemic heart disease, chronic obstructive pulmonary disease, and polypharmacy.

Aging without Dementia is Achievable: Current Evidence from Epidemiological Research

Both the incidence and the prevalence of dementia increase exponentially with increasing age. This raises the question of whether dementia is an inevitable consequence of aging or whether aging without dementia is achievable. In this review article, we sought to summarize the current evidence from epidemiological and neuropathological studies that investigated this topic. Epidemiological studies have shown that dementia could be avoided even at extreme old ages (e.g., centenarians or supercentenarians). Furthermore, clinico-neuropathological studies found that nearly half of centenarians with dementia did not have sufficient brain pathology to explain their cognitive symptoms, while intermediate-to-high Alzheimer pathology was present in around one-third of very old people without dementia or cognitive impairment. This suggests that certain compensatory mechanisms (e.g., cognitive reserve or resilience) may play a role in helping people in extreme old ages escape dementia syndrome. Finally, evidence has been accumulating in recent years indicating that the incidence of dementia has declined in Europe and North America, which supports the view that the risk of dementia in late life is modifiable. Evidence has emerged that intervention strategies that promote general health, maintain vascular health, and increase cognitive reserve are likely to help preserve cognitive function till late life, thus achieving the goal of aging without dementia.

Cell-free DNA as a biomarker of aging

Cell-free DNA (cfDNA) is present in the circulating plasma and other body fluids and is known to originate mainly from apoptotic cells. Here, we provide the first in vivo evidence of global and local chromatin changes in human aging by analyzing cfDNA from the blood of individuals of different age groups. Our results show that nucleosome signals inferred from cfDNA are consistent with the redistribution of heterochromatin observed in cellular senescence and aging in other model systems. In addition, we detected a relative cfDNA loss at several genomic locations, such as transcription start and termination sites, 5'UTR of L1HS retrotransposons and dimeric AluY elements with age. Our results also revealed age and deteriorating health status correlate with increased enrichment of signals from cells in different tissues. In conclusion, our results show that the sequencing of circulating cfDNA from human blood plasma can be used as a noninvasive methodology to study age-associated changes to the epigenome in vivo.

Apolipoprotein E gene in physiological and pathological aging

INTRODUCTION

The genetic background plays a role on longevity. The distribution of the apolipoprotein E gene (APOE) variants (ε2, ε3, ε4) may differ across age groups, especially in the oldest old and despite geographical and ethnic specificities. Since the ε4 variant is associated with Alzheimer's disease (AD), it might represent an opportunity for exploring the relationship of APOE with physiological and pathological aging.

AIM

To explore the role played by APOE genotype/alleles on physiological and pathological brain aging.

MATERIALS AND METHODS

The study was conducted in a cohort of centenarians (n = 106), and two cohorts of octogenarians (without cognitive decline, n = 351 controls; and with AD, n = 294).

RESULTS

No significant differences in genotype/allele distributions were observed comparing controls to centenarians. The prevalence of ε2/ε3, ε3/ε3, ε3/ε4 and ε4/ε4 genotypes were significantly different in centenarians compared to AD. The prevalence of ε2 and ε3 alleles were significantly higher in centenarians, whereas the ε4 was less frequent. The ε4 allele was positively associated with AD, whereas a negative association was found for ε2 and ε3 alleles.

CONCLUSIONS

Our study indicates that ε4 allele is strongly associated with AD. APOE significantly affects AD risk, but apparently not longevity.

Neuropsychological Test Performance of Cognitively Healthy Centenarians: Normative Data From the Dutch 100-Plus Study

OBJECTIVES

The fraction of the population that reaches the age of 100 years is growing. At this age, dementia incidence is high and cognitive functioning is highly variable across individuals. Normative data for neuropsychological tests are lacking in centenarians, which hampers the ability to evaluate their cognitive functioning for both research and clinical practice. Here, we generated norms for neuropsychological tests in a sample of cognitively healthy centenarians while taking sensory impairments into account.

DESIGN

Cross-sectional cohort study.

SETTING

Centenarians who participate in the prospective 100-plus Study.

PARTICIPANTS

A total of 235 centenarians (71.5% female), who self-reported to be cognitively healthy, which was confirmed by an informant and a trained researcher.

MEASUREMENTS

We generated normative data for 15 cognitive tests, measuring global cognition (Mini-Mental State Examination [MMSE]), premorbid intelligence, attention, language, memory, executive function, and visuospatial function by multiple linear regressions and/or by reporting percentiles.

RESULTS

Normative data for global cognition resulted in a mean MMSE score of 25.6 ± 3.1 (range = 17-30; interquartile range = 24-28). Vision problems and fatigue often complicated the ability to complete tests, and these problems explained 41% and 22% of the missing test scores, respectively. In contrast, hearing problems (4%) and task incomprehension (6%) rarely complicated test performance. While educational level was associated with performance on the majority of the tests, sex and age were only weakly associated with test performance.

CONCLUSIONS

We generated normative data for 15 common neuropsychological tests in a large sample of cognitively healthy centenarians, while taking age-related sensory impairments into consideration. These normative data allow the detection of deficits across a wide range of cognitive domains. Our results suggest that, next to education level, vision ability and the level of fatigue should be taken into account when evaluating cognitive functioning in centenarians. J Am Geriatr Soc 67:759-767, 2019.

Prevalence of Morbidity at Extreme Old Age in Germany: An Observational Study Using Health Claims Data

We assessed the prevalence of morbidity in long-lived individuals according to age and age at death and explored the association between dementia and other diseases and surviving to age 90 and 100. Using health claims data from the largest German health insurer from 2004 to 2013, we followed birth cohorts from 1908 to 1913 from age 95 until death or survival to age 100 (n=2,865) and compared them with birth cohorts from 1918 to 1923 and their survival from age 85 to age 90 (n=17,013). We observed their exact date of death and main categories of morbidity based on International Classification of Diseases, Tenth Revision, diagnoses. For all diseases studied, when differentiated according to age at death, prevalence continued to increase with age. Nonagenarians and centenarians had significantly lower disease prevalence at each age. Dementia was associated with the highest risk of dying before becoming a centenarian (hazard ratio (HR)=1.63, 95% confidence interval (CI)=1.50-1.78), followed closely by the residual category other chronic heart disease (HR=1.42, 95% CI=1.30-1.56). Results were even stronger for the younger cohort. Our study shows that exceptionally long-lived individuals are different in terms of good health. Survival at these high ages depends primarily on the absence of dementia and chronic heart disease, with acute heart disease and pneumonia playing important roles as diseases leading directly to death.

Long-term Care Status in Centenarians and Younger Cohorts of Oldest Old in the Last 6 Years of Life: Trajectories and Potential Mechanisms

OBJECTIVES

A large proportion of the oldest old and centenarians live in long-term care facilities. Although there may be distinct care patterns in centenarians compared with other cohorts of oldest old, the exact development concerning prevalence, length of stay, and factors that are associated with long-term care status in the last years before death is unknown.

DESIGN

Longitudinal analyses of health insurance data across 6 years before death.

SETTING AND PARTICIPANTS

In all, 1398 institutionalized and noninstitutionalized oldest old [deceased at 80-89 (octogenarians), 90-99 (nonagenarians), or over 100 years of age (centenarians)] from Germany were included. Long-term care status and transition from home care into long-term care over 6 years (34,740 person-quarters).

MEASUREMENTS

Dementia, musculoskeletal diseases, multimorbidity, hospital admission, gender, and age at death were derived from administrative data and analyzed using binary generalized estimating equations.

RESULTS

Although the initial level of long-term care (6 years before death) was higher among centenarians (65.1% vs 53.6% in nonagenarians; 36.2% in octogenarians), the rate of increase was stronger in the younger cohorts. Distinguishing between long-term care escapers, delayers, and survivors, the proportion of those who escaped, delayed, or survived the entire 6 years of observation in long-term care was 33.4%/40.4%/26.2% in centenarians, 45.0%/45.1%/9.9% in nonagenarians, and 62.7%/33.7%/3.6% in octogenarians. Age, hospital admissions, and dementia were positively associated with being in long-term care, whereas musculoskeletal disorders were negatively associated with long-term care. The association with dementia was significantly weaker in centenarians.

CONCLUSIONS

For centenarians, although they are more often in long-term care, the transition rate to long-term care progressed more slowly than the rates of the younger comparison cohorts of oldest old. The high proportion of long stays of centenarians in long-term care facilities require different concepts of long-term care.

Gut microbiota changes in the extreme decades of human life: a focus on centenarians

The gut microbiota (GM) is a complex, evolutionarily molded ecological system, which contributes to a variety of physiological functions. The GM is highly dynamic, being sensitive to environmental stimuli, and its composition changes over the host's entire lifespan. However, the basic question of how much these changes may be ascribed to variables such as population, diet, genetics and gender, and/or to the aging process per se is still largely unanswered. We argue that comparison among studies on centenarians-the best model of healthy aging and longevity-recruited from different geographical areas/populations (different genetics and dietary habits) can help to disentangle the contribution of aging and non-aging-related variables to GM remodeling with age. The current review focuses on the role of population, gender and host genetics as possible drivers of GM modification along the human aging process. The feedback impact of age-associated GM variation on the GM-brain axis and GM metabolomics is also discussed. We likewise address the role of GM in neurodegenerative diseases such as Parkinson's and Alzheimer's, and its possible therapeutic use, taking advantage of the fact that centenarians are characterized by an extreme (healthy) phenotype versus patients suffering from age-related pathologies. Finally, it is argued that longitudinal studies combining metagenomics sequencing and in-depth phylogenetic analysis with a comprehensive phenotypic characterization of centenarians and patients using up-to-date omics (metabolomics, transcriptomics and meta-transcriptomics) are urgently needed.