Relationship of low muscle mass and obesity with physical function in community dwelling older adults: Results from the Nagahama study

AimRelationships of low muscle mass and obesity with physical function were investigated in older adults.MethodsThe participants were 1922 community dwelling persons aged 60 years or older (67.7 ± 5.2 years old, 643 men and 1279 women). One-leg standing time, knee extensor muscle strength, and maximum walking speed were assessed. Muscle mass was evaluated using the bioelectrical impedance analysis (BIA) method, and skeletal mass index (SMI) was determined. For the obesity index, waist circumference with a stronger association with visceral fat was used. Participants were classified into the following four groups based on standard values of waist circumference and SMI: non-obese low-SMI, obese low-SMI, non-obese normal-SMI, and obese normal-SMI.ResultsBy two-way analysis of variance (obesity × SMI), the main effects of waist circumference and muscle mass were noted in the one-leg standing time. The maximum walking speed was higher in the non-obese than the obese group, and in the normal than the low SMI group. In the muscle strength, a main effect was noted only in the muscle mass of women. An interaction was noted in men and significant differences were detected between all combinations except between the non-obese low SMI and obese low SMI groups.ConclusionLow muscle mass and obesity negatively influence balance and walking abilities. However, the influence of low muscle mass and obesity on muscle strength were different between the sexes. In men, the relationship between obesity and muscle strength would be different depending on whether muscle mass is retained.     

Phase angle predicts physical function in older adults

BackgroundPhase angle (PhA) is recognized as an indicator of cellular health and may be a useful marker of physical functions in geriatric populations.AimsWe aim to analyse the ability of the Phase angle (PhA) to predict the physical function in older adults.Method113 healthy older adults (67 female and 46 male) performed physical tests using the Fullerton Battery – Senior Fitness Test, to assess their physical fitness. Bioelectrical impedance spectroscopy was used to determine PhA at 50KHz and dual-energy x-ray absorptiometry to assess body composition.ResultsPhA was positively associated with functional fitness composite, chair stand, arm curl and 6 min walk test and negatively related with chair sit-and-reach and 8-foot and go (p < 0.05). Even after adjusting for potential confounding variables such as age, sex and appendicular lean soft tissue, PhA showed an association with arm curl (ß = 0.23,p = 0.038), and 8-foot and go (ß=-0.214,p = 0.042).ConclusionsHigher values of PhA are related with a better physical function. Regardless of sex, age, and skeletal muscle, PhA predicts body strength, agility and dynamic balance in healthy older adults.     

Associations of breaks in sedentary time with abdominal obesity in Portuguese older adults

In older adults, sedentary time is positively associated with obesity. The manner in which it is accumulated, i.e., the number of breaks in sedentary time, might be also important. We examined the cross-sectional associations of breaks in sedentary time with abdominal obesity in 301 older adults (111 men and 190 women) aged 75.0 ± 6.8 years. Sedentary time (counts min⁻¹ < 100) and physical activity were objectively measured by accelerometry, worn during waking hours for at least three consecutive days. A break was defined as an interruption (≥100 counts min⁻¹ < 2020) in sedentary time while performing light intensity physical activities. Sedentary time was expressed as the number of daily breaks in sedentary time or hourly breaks in sedentary time. Abdominal obesity was defined by waist circumference (men >102 cm; women >88 cm). Using binary logistic regression analyses, the odds for abdominal obesity decreased 7 % for each additional hourly break in sedentary time in women (OR = 0.93, 95 % CI: 0.87–1.00), but not men, independently of total sedentary time and moderate-to-vigorous physical activity. The odds for abdominal obesity were 3.21 times higher (p = 0.039) for women in quartile 1 (<225 breaks day⁻¹) of daily breaks in sedentary time compared to those in quartile 4 (>353 breaks day⁻¹) of daily breaks in sedentary time.These findings indicate that older women who interrupt their sedentary time more frequently are less likely to present abdominal obesity. Public health recommendations regarding breaking-up sedentary time complementary to those for physical activity are likely to be relevant.     

Influences of body mass index and waist circumference on physical function in older persons with heart failure

BACKGROUND:

In older persons with heart failure (HF), body composition may influence physical function and treatment effectiveness. There is a lack of research concerning the associations between waist circumference (WC) or body mass index (BMI) and physical function in this population.

OBJECTIVE:

To determine whether BMI and WC are associated with physical function in older men and women with HF.

METHODS:

Seventy-one men and 36 women 65 years of age and older living with HF completed two surveys spaced three months apart. Height, weight, WC, time since diagnosis, edema, comorbidities and physical function were self-reported at baseline and follow-up. Physical function was determined using the physical component score of the Short Form-12 and the physical limitation domain (PLD) of the Kansas City Cardiomyopathy Questionnaire. Multivariate linear regression and analysis of covariance were used to evaluate the relationships between WC and BMI, as well as cross-classifications of WC and BMI with physical function, after adjusting for confounders and interactions.

RESULTS:

The cross-sectional and short-term follow-up analyses did not detect an association between WC or BMI and physical function, with the exception of changes in the PLD, which were significantly different across WC categories. Persons with a moderate WC experienced the greatest improvement in function. The physical component and PLD scores were lower than those reported by Canadians 75 years of age and older and stable HF patients, respectively. Women reported lower physical function scores than men.

CONCLUSION:

Findings from the present study indicate that older persons with HF, especially women, have poor physical functioning regardless of their WC or BMI.     

Body composition and frailty profiles in Brazilian older people: Frailty in Brazilian Older People Study-FIBRA-BR

ObjectiveTo determine the association between body composition and frailty in older Brazilian subjects.Material and methodsThis is a Cross-sectional study called FIBRA-BR and developed in community Brazilian aged ≥65 (n = 5638). Frailty was assessed according to Fried et al. definition and body composition was determined by BMI, waist circumference and waist-hip ratio.ResultsThe lowest prevalence of frailty was observed in subjects with BMI between 25.0 and 29.9 kg/m². Subjects with a BMI <18.5 and those with elevated WC presented a higher risk of frailty compared to eutrophic subjects (odds ratio (OR) = 3.10; 95% CI: 2.06–4.67) and (OR = 1.15; 95% CI: 1.03–1.27), respectively. Being overweight was protective for pre-frailty (OR = 0.48; 95% CI: 0.4–0.58) and frailty (OR = 0.77; 95% CI: 0.67–0.9). Obese older people presented a higher risk of pre-frailty only (OR = 1.29; 95% CI: 1.09–1.51). Older people with high WC showed a greater proportion of frailty regardless of the BMI range.ConclusionUndernutrition is associated with pre-frailty and frailty in Brazilian elderly subjects, whereas obesity is associated only with pre-frailty. Overweight seems to have a protective effect against the syndrome. The excess of abdominal fat is associated with both profiles independent of the BMI.     

Obesity,intentional weight loss and physical disability in older adults

We examine obesity, intentional weight loss and physical disability in older adults. Based on prospective epidemiological studies, body mass index exhibits a curvilinear relationship with physical disability; there appears to be some protective effect associated with older adults being overweight. Whereas the greatest risk for physical disability occurs in older adults who are ≥class II obesity, the effects of obesity on physical disability appears to be moderated by both sex and race. Obesity at age 30 years constitutes a greater risk for disability later in life than when obesity develops at age 50 years or later; however, physical activity may buffer the adverse effects obesity has on late life physical disability. Data from a limited number of randomized clinical trials reinforce the important role that physical activity plays in weight loss programmes for older adults. Furthermore, short‐term studies have found that resistance training may be particularly beneficial in these programmes as this mode of exercise attenuates the loss of fat‐free mass during caloric restriction. Multi‐year randomized clinical trials are needed to examine whether weight loss can alter the course of physical disablement in aging and to determine the long‐term feasibility and effects of combining resistance exercise with weight loss in older adults.     

Sedentary behavior and physical activity are independently related to functional fitness in older adults

The last decades of life have been traditionally viewed as a time of inevitable disease and frailty. Sedentary living and physical activity may influence capacity to perform activities that are needed to maintain physical independence in daily living. A total of 117 males and 195 females, aged 65–103 years, were assessed for physical activity and sedentary time with accelerometers and for functional fitness with the Senior Fitness Test battery. Based on the individual scores for each fitness item, a Z-score was created. Associations between functional fitness with sedentary time and moderate-to-vigorous physical activity (MVPA) were analyzed. A negative association was found between the composite Z-score for functional fitness and the sedentary time, even adjusting for MVPA and other confounders. On the other hand, MVPA was positively associated with the composite Z-score for functional fitness, independently of the sedentary time. In conclusion elderly who spend more time in physical activity or less time in sedentary behaviors exhibit improved functional fitness and other confounders. The results reinforce the importance of promoting both the reduction of sedentary behaviors and the increase of MVPA in this age group, as it may interfere at older ages in order to preserve functional fitness and performance of daily functioning tasks.     

Nutritional status is associated with physical function and disability in older adults with chronic heart failure

BackgroundThe association between nutritional status (NS) and physical performance and disability in older adults with chronic heart failure (CHF) is not well established. We aimed at evaluating whether NS, estimated using the Mini Nutritional Assessment (MNA), is associated with gait speed (GS) and disability (ADL/IADL impairment) in this population and to assess whether energy intake (EI) and appendicular skeletal muscle mass index (ASMMI) influence this relationship.MethodsIn this cross-sectional study we enrolled 88 older adults admitted to a cardiology outpatient clinic for CHF. MNA was analyzed both as continuous and categorical variable (risk of malnutrition [RM]/well-nourished [WN]). The association between NS and GS and disability was assessed using linear and logistic regression models, respectively, crude, adjusted firstly for age, sex, ejection fraction, and mood status, and then for EI and ASMMI.ResultsMean age was 77.8 years, 73% were men. MNA score was positively associated with GS: β adjusted = 0.022, P = 0.035; the coefficient was unaffected by adjustment for EI and ASMMI (β = 0.022, P = 0.052). Compared to WN, RM participants had a lower gait speed (0.82 vs 0.99 m/s, P = 0.006); the difference was attenuated after adjustment for potential confounders (β − = 0.138, P = 0.055). MNA score was inversely associated with ADL impairment (Adjusted OR: 0.80, 95%CI 0.64–0.98), but not with IADL impairment (Adjusted OR: 0.94, 95%CI 0.78–1.13).ConclusionReduced MNA score is associated with poorer physical function and ADL impairment in older adults affected by CHF, independently of EI and ASMMI. Routinely evaluation of NS should be performed in this population.     

Protein intake is not associated with functional biomarkers of physical frailty: A cross-sectional analysis of community-dwelling older adults with type 2 diabetes mellitus

Background and aimFrailty has emerged as a third category of complication in patients with type 2 diabetes mellitus (T2DM). It has been suggested that adequate protein intake is an important dietary strategy for counteracting frailty. Therefore, we explored the association between protein intake and functional biomarkers of frailty in older adults with T2DM.Methods and resultsFrailty was operationalized as the presence of three of the following: exhaustion, low muscle strength, low physical activity, slow gait speed, and weight loss. Functional biomarkers included handgrip strength (HGS), chair stands, the short physical performance battery and gait speed. Eighty-seven older adults (71.2 ± 8.2 years; 66.7% males) were included. A total of n = 6 (~7%) and n = 32 (~37%) participants were identified as frail and pre-frail respectively. No significant difference was observed for protein intake across staging of frailty (pre-frail/frail: 1.3 ± 0.4 g/kg BW; non-frail: 1.4 ± 0.4 g/kg BW; P = 0.320). A significant association was observed for total protein intake and HGS (β = 0.44; 95% CI: 0.23–1.8; P = 0.01). However, this was no longer significant after adjusting for age, gender, physical activity, energy intake and total appendicular lean muscle (β = 0.03; 95% CI: ?0.45–0.60; P = 0.78). Nil other associations were observed between total protein intake and functional biomarkers of frailty.ConclusionAdequate protein intake was not associated with functional biomarkers in older adults with T2DM. Future research should focus on the efficacy of protein on attenuating functional decline in vulnerable older adults with low protein intake.     

Comparison of the physical fitness levels in nursing home residents and community-dwelling older adults

PurposeThis study aimed to compare the physical fitness levels of nursing home residents and community-dwelling older adults.Materials and methodsThe 118 older adults aged between 65–85 living in a nursing home or community participated in the study. The Senior Fitness Test assessed the physical fitness levels of older adults. The older adults performed the chair stand test, arm curl test, 2-min step test, chair sit and reach test, back-scratch test, 8-foot up, and go test.ResultsThe age, cognitive status, gender, body weight, height, smoking, and education status were similar between the groups (p > 0.05). Aerobic endurance, balance, and agility were higher in nursing home residents than in the community-dwelling older adults (p < 0.05). Strength, flexibility, and BMI did not differ between groups ​​(p > 0.05).ConclusionAerobic endurance, balance, and agility may vary depending on the living environment of older adults. The determination of differences in physical fitness between community-dwelling older adults and nursing home residents could provide objective information to develop a physical activity program for older adults.     

Optimal waist circumference cutoff values for predicting metabolic syndrome among older adults in Ecuador

AimsTo determine optimal waist circumference cutoff values for predicting metabolic syndrome (MetS) among adults aged 60 years and older in Ecuador.Material and methodsThe National Survey of Health, Wellbeing, and Aging survey was used to describe the prevalence of MetS according to standard definitions. Receiver operating characteristics (ROC) curve analyses and the Younden index J (YI) were performed to examine optimal waist circumference cutoff values for predicting MetS. Moreover, the prevalence of MetS according to country-specific waist circumference cutoff values was compared with those using standard definitions.ResultsAmong 2306 participants with a mean age of 70.6 years, the optimal waist circumference cutoff value for predicting MetS was 90.7 cm in women with a sensitivity of 66.1%, specificity of 65.6% and YI of 0.31. In men, a waist circumference of 91.2 cm with a sensitivity of 73.2%, specificity of 62.8%, and YI of 0.36 was the optimal cutoff point for predicting MetS. In general, applying country-specific cutoff values decreased the prevalence of MetS among older Ecuadorian women. In men, except with the ATP III definition, similar MetS prevalence rates were seen whether the country-specific or standard waist circumference cutoff values were applied.ConclusionsThe optimal waist circumference cutoff values for predicting metabolic syndrome among older Ecuadorians adults were 90.7 cm for women and 91.2 cm for men. Moreover, current standard definitions of abdominal obesity may overestimate the prevalence of MetS, particularly in Latin American women.     

NK cell immunesenescence is increased by psychological but not physical stress in older adults associated with raised cortisol and reduced perforin expression

NK cell cytotoxicity (NKCC) reduces with age and this has been associated previously with increased mortality. The immune response is also modulated by stress, and here, we assessed the effect of the physical stress of hip fracture and the psychological stress of depression on NKCC in an aged immune system. NKCC was assessed in 101 hip fracture patients (81 female) 6 weeks and 6 months after injury and in 50 healthy age-matched controls (28 female). Thirty-eight patients were depressed at 6 weeks post-injury, and NKCC was reduced in patients who developed depression compared with non-depressed hip fracture patients (p = 0.004) or controls (p < 0.02). NKCC remained lower in the depressed patients compared to those without depression 6 months post-fracture (p = 0.017). We found reduced expression of perforin in NK cells of depressed hip fracture patients compared with controls at 6 weeks (p = 0.001) post-fracture. Serum cortisol levels were also elevated in patients with depression compared to non-depressed patients at 6 weeks (p = 0.01) and 6 months (p = 0.05). NK cells treated with dexamethasone showed a concentration-dependent reduction in NKCC and perforin expression. We propose that depression is the major factor affecting NK cell immunity after hip fracture.     

Asthma is associated with weight gain in females but not males, independent of physical activity.

We tested whether asthma diagnosis is associated with weight gain and physical activity in 4,547 18 to 30-yr-old African American and white men and women, followed prospectively for up to 10 yr. Baseline asthma was most frequent in African American men. Incident asthma was more frequent in women. Incident asthma was associated with highest and lowest baseline and change in body mass index (BMI), in a J-shaped curve, after adjustment for other factors. When stratified by sex, this association was seen only in females. Subjects on average decreased physical activity and gained weight over time, but there was no significant difference in asthma prevalence by physical activity at baseline or asthma incidence by change in physical activity. Cigarette smoking in females was significantly associated with asthma incidence, but serum cotinine level at baseline among nonsmokers (reflecting environmental tobacco smoke [ETS] exposure) was not significantly associated with asthma. We conclude that gain in BMI predisposes to new asthma diagnosis in female young adults, but decreased physical activity does not explain the association of weight gain with asthma.     

Increased waist circumference is associated with subclinical atherosclerosis in schoolchildren

BackgroundWaist circumference (WC) is an indicator of adiposity; particularly visceral fat, cardiometabolic risk factors and related morbidity. The aim of this study was to determine the attribution of WC to increased carotid intima-media thickness (cIMT) and circulating levels of inflammation and endothelial dysfunction in schoolchildren.MethodsA total of 122 children (61 boys and 61 girls) aged 10–15 years were distributed into three groups: (i) the lower smoothed sex- and age-specific WC (LWC) group (ii) the middle smoothed sex- and age-specific WC (MWC) group, and (iii) the higher smoothed sex- and age-specific WC (HWC) group. Measurements of cIMT using high-resolution B-mode ultrasound, lipemic profile, blood pressure, serum proinflammatory cytokines and soluble adhesion molecules were performed.ResultsMean measured values in the HWC and/or MWC groups showed significantly higher values (p ≤ 0.05) of cIMT (mm), total cholesterol, triglycerides, low-density lipoprotein (LDL), blood pressure, interlukien-6 (IL-6), and interlukien-1 beta (IL-1β), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1(ICAM-1) and E-selectin, and significantly lower values of high-density lipoprotein (HDL) as compared to the LWC group. Using multiple linear regression analysis of WC-SDS adjusted for BMI-SDS with the studied subclinical atherosclerosis risk, WC-SDS was significantly (p ≤ 0.05) associated with the variation in HDL (R² = −0.12), LDL (R² = 0.36), IL-6 (R² = 0.26), and VCAM-1 (R² = 0.26).ConclusionsHigher WC is positively associated with atherosclerosis risk factors including increased cIMT, a state of dyslipidemia, higher blood pressure and circulating levels of inflammation and adhesion molecules among schoolchildren. Waist circumference seems to be useful for the prediction of subclinical atherosclerosis in schoolchildren.     

Effect of physical activity on functional status among older middle‐age adults with arthritis

Objective

To determine the effect of leisure time and work‐related physical activity on changes in physical functioning among 3,554 nationally representative survey respondents, ages 53–63 years in 1994, with arthritis and joint symptoms, interviewed in the Health and Retirement Study (HRS).

Methods

In 1992–1994, light and vigorous exercise items were empirically categorized into recommended, insufficient, and inactive leisure time physical activity levels using data from the HRS. Leisure and work‐related physical activity levels in 1994 were used to predict 1996 functional decline or improvement, controlling for baseline functional difficulties, health status, sociodemographic characteristics, and behavioral risk factors.

Results

Whereas 29.7% of respondents reported functional declines in 1996, 38.6% of those with baseline difficulties in 1994 reported improvement. Compared with inactive respondents, recommended and insufficient leisure time physical activity were equally protective against functional decline (odds ratio [OR] 0.59 and 0.62, respectively; P < 0.0001). Higher levels of physical activity were also modestly associated with functional improvement among respondents with baseline functional difficulties (OR 1.47, P = 0.05 and OR 1.45, P = 0.01, respectively). Work‐related physical activity was not a significant predictor of decline or improvement.

Conclusion

Given the high prevalence of arthritis, even modest increases in rates of lifestyle physical activity among older adults could make a substantial contribution to disability‐free life expectancy.

     

Dietary patterns of rural older adults are associated with weight and nutritional status

OBJECTIVES: To characterize dietary patterns of rural older adults and relate patterns to weight and nutritional status. DESIGN: Cross-sectional. SETTING: Rural Pennsylvania. PARTICIPANTS: One hundred seventy-nine community-dwelling adults aged 66 to 87 years. MEASUREMENTS: A home visit was conducted to collect demographic, health behavior, and anthropometric data and a blood sample. Five 24-hour dietary recall were administered. Cluster analysis classified participants into dietary patterns using food subgroup servings. Chi-square, analysis of covariance, and logistic regression were used to assess differences across clusters. RESULTS: A low-nutrient-dense cluster (n=107), with higher intake of breads, sweet breads/desserts, dairy desserts, processed meats, eggs, and fats/oils, and a high-nutrient-dense cluster (n=72) with higher intake of cereals, dark green/yellow vegetables, other vegetables, citrus/melons/berries, fruit juices, other fruits, milks, poultry, fish, and beans, were identified. Those in the high-nutrient-dense cluster had lower energy intake; higher energy-adjusted intake of fiber, iron, zinc, folate, and vitamins B(6), B(12), and D; higher Healthy Eating Index scores; higher plasma vitamin B(12) levels; and a lower waist circumference. Those with a low-nutrient-dense dietary pattern were twice as likely to be obese, twice as likely to have low plasma vitamin B(12) levels, and three to 17 times more likely to have low nutrient intake. CONCLUSION: This study provides support for recommending a high-nutrient-dense dietary pattern for older adults. Behavioral interventions encouraging diets characterized by high-nutrient-dense foods may improve weight and nutritional status of older adults.     

The effects of physical activity, body mass index (BMI) and waist circumference (WC) on glucose intolerance in older people: A nationwide study from Taiwan

We investigated the gender-specific effects of physical activity, BMI and WC on glucose intolerance in an elderly Taiwanese population (n = 1344) aged 65 and above, who participated in the Elderly Nutrition and Health Survey in Taiwan in 1999-2000. In this cross-sectional study, physical activity was assessed using the Modified Baecke Questionnaire for Older Adults (MBQOA). Categories of physical activity level were defined by tertiles of MBQOA scores. Glucose intolerance in subjects not previously diagnosed with diabetes was categorized according to 2003 American Diabetes Association criteria. After adjustment for potential confounders, physical activity was significantly inversely associated with the presence of undiagnosed type 2 diabetes and impaired fasting glucose (IFG) in older women. In older men, the association was less clear. BMI and WC were significantly positively associated with the presence of undiagnosed diabetes in men and were significantly associated with IFG in both sexes. In older women, undiagnosed diabetes was strongly associated with increased WC, but not with BMI. Our findings highlight that older women with low physical activity or high WC, and older men with high BMI or WC are important target populations for interventions to prevent glucose intolerance.     

Small bowel bacterial overgrowth is not seen in healthy adults but is in disabled older adults

BACKGROUND/AIMS: Small bowel bacterial overgrowth (SBBO) is defined as an abnormal increase in the number of bacteria in the small intestine, and may be occult in older adults. The aim of this study was to determine whether small bowel bacterial overgrowth (SBBO) is found in healthy older people as a concomitant of normal aging or is seen only in disabled or frail older people, excluding patients with intestinal disease and those who had undergone upper intestinal or gastric surgery. METHODOLOGY: Forty-one relatively healthy older people, aged 74.6 +/- 1.7 (mean +/- SE) years, who engage in regular exercise, and 42 variously disabled older people, average age 78.8 +/- 1.1 years, who commute to a day-care center participated in this study. SBBO was determined by a breath hydrogen (H2) test after ingestion of 50g of glucose solution dissolved in 200mL of water. Physical activity was judged from the number of steps walked per day as measured by a pedometer. Food intake was assessed by an interview. RESULTS: No SBBO-positive subject was seen among the healthy, while 11 (25.6%) of the disabled older adults were positive. The number of steps/day taken by the disabled subjects was extremely low, only 22.3% of that of the healthy (P<0.001). No significant difference was seen between the groups in food intake. The mean age of the SBBO-positive patients was relatively high, 81.5 +/- 2.2 years, and 5 (45.4%) of them were underweight, with a BMI<18.5. CONCLUSIONS: Our results and previous studies indicate that SBBO is seen only in patients with intestinal disease and disabled or frail older people.     

Divided attention in older but not younger adults is impaired by anxiety

It has been hypothesized that the disruptive effects of negative emotional states, such as anxiety and depression, may contribute to poorer performance in older age. Some studies have reported that higher levels of anxiety are associated with poorer cognitive performance in older adults but not younger adults. The author examined if age and anxiety interact with performance by comparing the performance of normal healthy younger and older adults on cognitive and motor tests under conditions of selective and divided attention. Ninety-two older adults (mean age=70.1 years, SD=7.1 years) and 78 younger adults (mean age=18.8 years, SD=1.9 years), matched on education, vocabulary, and self-reported health, performed a word-comparison and pursuit-rotor task under conditions of selective and divided attention. Anxiety was assessed using the Speilberger State-Trait anxiety scale. The hypothesis was supported: higher anxiety was associated with poorer divided attention performance in older, but not younger, adults. Anxiety was not associated with poorer motor performance in older adults. Implications of the results for cognitive-resource theories of aging cognition are discussed.