The measurement of mobility is essential to both aging research and clinical practice. A newly developed self-report measure of mobility, the mobility assessment tool—short form (MAT-sf), uses video animations to improve measurement accuracy/precision. Using a large baseline data set, we recalibrated the items, evaluated the extent to which older patients’ self-efficacy (i.e., confidence) for walking was related to MAT-sf scores beyond their actual 400-m walk time, and assessed the relationship of the MAT-sf with body mass index and other clinical variables.
The analyses employed baseline data from the Lifestyle Interventions and Independence for Elders Study.
Item recalibration demonstrated that the MAT-sf scoring algorithm was robust. In an analysis with 400-m walk time and self-efficacy regressed on the MAT-sf, both variables shared unique variance with the MAT-sf (p < .001). The MAT-sf was inversely related to several comorbidities, most notably hypertension and arthritis (p < .001), and scores were lowest when body mass index ≥ 35kg/m2. Finally, MAT-sf scores were directly related to Short Physical Performance Battery scores, inversely related to difficulty with activities of daily living (p < .001) and higher for men than for women (p < .001).
The findings extend the validity and clinical utility of this innovative tool for assessing self-reported mobility in older adults. Longitudinal data on the MAT-sf from the Lifestyle Interventions and Independence for Elders Study will enable us to evaluate the relative contributions of self-report and performance-based measures of mobility on important health outcomes.
Mobility; Geriatric assessment; Physical function; MAT-sf
The Lifestyle Interventions and Independence for Elders (LIFE) Study is a Phase III randomized controlled clinical trial (Clinicaltrials.gov identifier: NCT01072500) that will provide definitive evidence regarding the effect of physical activity (PA) on major mobility disability in older adults (70–89 years old) who have compromised physical function. This paper describes the methods employed in the delivery of the LIFE Study PA intervention, providing insight into how we promoted adherence and monitored the fidelity of treatment. Data are presented on participants’ motives and self-perceptions at the onset of the trial along with accelerometry data on patterns of PA during exercise training. Prior to the onset of training, 31.4% of participants noted slight conflict with being able to meet the demands of the program and 6.4% indicated that the degree of conflict would be moderate. Accelerometry data collected during PA training revealed that the average intensity – 1,555 counts/minute for men and 1,237 counts/minute for women – was well below the cutoff point used to classify exercise as being of moderate intensity or higher for adults. Also, a sizable subgroup required one or more rest stops. These data illustrate that it is not feasible to have a single exercise prescription for older adults with compromised function. Moreover, the concept of what constitutes “moderate” exercise or an appropriate volume of work is dictated by the physical capacities of each individual and the level of comfort/stability in actually executing a specific prescription.
aging; accelerometry; physical disability; compromised physical function; older adults
Considerable research over the past decade has garnered support for the notion that the mind is both embodied and relational. Jointly, these terms imply that the brain, physical attributes of the self, and features of our interpersonal relationships and of the environments in which we live jointly regulate energy and information flow; they codetermine how we think, feel, and behave both individually and collectively. In addition to direct experience, evidence supports the view that stimuli embedded within past memories trigger multimodal simulations throughout the body and brain to literally recreate lived experience. In this paper, we review empirical support for the concept of an embodied and relational mind and then reflect on the implications of this perspective for clinical interventions in aging individuals and populations. Data suggest that environmental influences literally “get under the skin” with aging; that musculoskeletal and visceral sensations become more prominent in activities of the mind due to aging biological systems and chronic disease. We argue that conceiving the mind as embodied and relational will grow scientific inquiry in aging, transform how we think about the self-system and well-being, and lead us to rethink health promotion interventions aimed at aging individuals and populations.
behavior change; gerontology; disablement; well-being; embodiment
The Power of Food Scale (PFS) is a new measure that assesses the drive to consume highly palatable food in an obesogenic food environment. The data reported in this investigation evaluate whether the PFS moderates state cravings, control beliefs, and brain networks of older, obese adults following either a short-term post-absorptive state, in which participants were only allowed to consume water, or a short-term energy surfeit treatment condition, in which they consumed BOOST®. We found that the short-term post-absorptive condition,in which participants consumed water only, was associated withincreases in state cravings for desired food, a reduction in participants' confidence related to the control of eating behavior, and shifts in brain networks that parallel what is observed with other addictive behaviors. Furthermore, individuals who scored high on the PFSwere at an increased risk for experiencing these effects. Future research is needed to examine the eating behavior of persons who score high on the PFS and to develop interventions that directly target food cravings.
aging; brain networks; food; cravings; self-efficacy
There is considerable interest in understanding food cravings given the obesogenic environment of Western Society. In this paper we examine how the imagery of palatable foods affects cravings and functional connectivity in the visual cortex for people who differ on the power of food scale (PFS). Fourteen older, overweight/obese adults came to our laboratory on two different occasions. Both times they ate a controlled breakfast meal and then were restricted from eating for 2.5 h prior to scanning. On 1 day they consumed a BOOST® liquid meal after the period of food restriction, whereas on the other day they only consumed water (NO BOOST® condition). After these manipulations, they had an fMRI scan in which they were asked to image both neutral objects and their favorite snack foods; they also completed visual analog scales for craving, hunger, and the vividness of the imagery experiences. Irrespective of the BOOST® manipulation, we observed marked increases in food cravings when older, overweight/obese adults created images of favorite foods in their minds as opposed to creating an image of neutral objects; however, the increase in food craving following the imagery of desired food was more pronounced among those scoring high than low on the PFS. Furthermore, local efficiency within the visual cortex when imaging desired food was higher for those scoring high as compared to low on the PFS. The active imagery of desired foods seemed to have overpowered the BOOST® manipulation when evaluating connectivity in the visual cortex.
food craving; network science; visual cortex; power of food scale; older adults
The obesity epidemic had spawned considerable interest in understanding peoples' responses to palatable food cues that are plentiful in obesogenic environments. In this paper we examine how trait mindfulness of older, obese adults may moderate brain networks that arise from exposure to such cues. Nineteen older, obese adults came to our laboratory on two different occasions. Both times they ate a controlled breakfast meal and then were restricted from eating for 2.5 h. After this brief period of food restriction, they had an fMRI scan in which they were exposed to food cues and then underwent a 5 min recovery period to evaluate brain networks at rest. On one day they consumed a BOOST® liquid meal prior to scanning, whereas on the other day they only consumed water (NO BOOST® condition). We found that adults high in trait mindfulness were able to return to their default mode network (DMN), as indicated by greater global efficiency in the precuneus, during the post-exposure rest period. This effect was stronger for the BOOST® than NO BOOST® treatment condition. Older adults low in trait mindfulness did not exhibit this pattern in the DMN. In fact, the brain networks of those low on the MAAS suggests that they continued to be pre-occupied with the elaboration of food cues even after cue exposure had ended. Further work is needed to examine whether mindfulness-based therapies alter brain networks to food cues and whether these changes are related to eating behavior.
networks; mindfulness; food cues; obesity; aging; craving; self-efficacy
We examine obesity, intentional weight loss, and physical disability in older adults. Based on prospective epidemiological studies, BMI 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 constitutes a greater risk for disability later in life than when obesity develops at age 50 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 (RCTs) reinforce the important role that physical activity plays in weight loss programs for older adults. Furthermore, short-term studies have found that resistance training may be particularly beneficial in these programs since this mode of exercise attenuates the loss of fat-free mass during caloric restriction. Multi-year RCTs 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.
Body-mass index (BMI); physical function; elderly; physical activity; exercise
The startle response has been shown to be useful in studying reactivity to food cues. Following 6h of food deprivation and exposure to neutral and food cues, we examined the role of state craving combined with both a short and long delay of consumption on affect and startle reflex. Participants completed the PANAS, consumed a controlled early morning meal, and experienced 6h of food deprivation. They then reported back to the laboratory, completed a second baseline PANAS, and had their baseline eyeblink EMG startle responses to 100 dB(A) startle probe assessed. Prior to and following the presentation of cues, startle probes were presented and responses were recorded. The PANAS and state craving were also assessed after each cue. Food cues provoked higher levels of state craving than neutral cues and startle responses failed to habituate as quickly to food cues as they did to neutral cues. In addition, cue exposure created the highest NA among high state cravers in the long delay of consumption group. Startle responses differed from NA in that with long delay startle was high irrespective of state craving scores; in the short delay of consumption condition, startle increased linearly with state craving. These results illustrate that state craving and expectations of food availability are important variables in understanding food-related cue reactivity.
Food Craving; Startle; Fasting; Negative Affect; Food Availability
Using the weight efficacy lifestyle questionnaire (WEL), we examined whether a group-mediated intervention for weight loss among older, obese adults resulted in changes in self-regulatory self-efficacy for eating behavior and whether these changes mediated weight loss.
This was a randomized controlled design, and 288 older adults received 1 of 3 treatments for 6 months: physical activity only (PA), weight loss + physical activity (WL + PA), or a successful aging (SA) health education program. The WEL was administered prior to randomization and again at the 6-month follow-up visit.
A significant treatment effect was observed for the WEL, F (2,249) = 15.11, p < .0001, partial eta2 = .11, showing that improvement occurred only in the WL + PA group as compared with PA and SA. Changes in WEL scores partially mediated the effects of the WL + PA intervention on weight loss.
These results illustrate that WL + PA can be effective in improving older adults’ self-efficacy for the self-regulation of eating behavior and that these changes are prospectively related to the amount of weight loss. Further research is warranted on an expanded concept of self-efficacy as well as controlled experimental studies on eating behavior in older adults.
Mindfulness; Older adults; PA; Self-efficacy; Weight loss
Existing self-report measures of mobility ignore important contextual features of movement and require respondents to make complex judgments about specific tasks. Thus, we describe the development and validation of a short form (sf) video-animated tool for assessing mobility, the Mobility Assessment Tool—MAT-sf.
This study involves cross-sectional and longitudinal analyses examining the measurement properties of the MAT-sf. The MAT-sf consists of 10 animated video clips that assess respondents’ level of proficiency in performing each task. The main outcome measures used for validation included the Pepper Assessment Tool for Disability (PAT-D), the Short Physical Performance Battery (SPPB), and 400-m walk test.
Participants (n = 234), 166 women and 68 men, had an average age of 81.9 years and a variety of comorbidities with 65.4% having high blood pressure. An average SPPB score of 8.6 (range 2–12) suggests that the study sample had evidence of compromised physical function but was quite heterogeneous. The MAT-sf had good content validity, excellent test–retest reliability (r = .93), and criterion-related validity with the PAT-D. Moreover, the MAT-sf added considerable variance to the prediction of both SPPB scores and 400-m gait speed over and above the PAT-D mobility subscale. The MAT-sf also discriminated between older adults who completed or failed the 400-m walk test.
The MAT-sf is an innovative psychometrically sound measure of mobility. It has utility in epidemiological studies, translational science, and clinical practice.
Mobility; Aging; Measurement; Disability
It is well recognized that physical activity (PA) is important for older adults; yet, clinicians remain pessimistic about the ability of older adults with compromised function to adhere to long-term treatment and to maintain behavior change once treatment has been terminated.
We examined the functional status of older adults at a field center (Wake Forest University) 2 years after completing 12 months of treatment in the Lifestyle Interventions and Independence for Elders Pilot study. At baseline, participants were randomized to either a PA or a successful aging (SA) control group. Outcome measures included an interview assessment of PA, the Short Physical Performance Battery (SPPB), and performance on a 400-m self-paced walking test.
Two years after the formal intervention had ended, participants who were originally in the PA group continued to engage in more minutes of moderate PA and tended to have better SPPB and walking speed than those in the SA group (effect sizes [ES]: SPPB = 0.40, walking speed = 0.37). Seven (12.7%) participants in the PA group failed the 400-m walk at the 36-month follow-up assessment, whereas this number was 11 (21.6%) in the SA group.
Older adults who have compromised physical function are able to sustain some of the benefits derived from participating in structured PA 2 years after supervised treatment has been terminated.
Aging; Disability; Mobility; SPPB; 400-m walk
Derived from Buddhism, mindfulness is a unique approach for understanding human suffering and happiness that has attracted rapidly growing interest among health care professionals. In this article I describe current thinking about the concept of mindfulness and elaborate on why and how mindfulness-based interventions have potential within the context of geriatric medicine and gerontology. Upon reviewing definitions and models of the concept, I give attention to the unique role that the body plays in cultivating mindfulness and the advantages that this focus has for older adults because they have aging biological systems and may experience chronic disease, pain, and disability. In the final section I discuss why mindfulness may be particularly useful in promoting physical activity among older adults and how physical activity may be used as a vehicle to promote mindfulness.
Disability; Interventions in aging; Pain; Physical activity
There is a need to identify evidenced-based obesity treatments that are effective in maintaining lost weight. Weight loss results in reductions in energy expenditure, including spontaneous physical activity (SPA) which is defined as energy expenditure resulting primarily from unstructured mobility-related activities that occur during daily life. To date, there is little research, especially randomized, controlled trials, testing strategies that can be adopted and sustained to prevent declines in SPA that occur with weight loss. Self-monitoring is a successful behavioral strategy to facilitate behavior change, so a provocative question is whether monitoring SPA-related energy expenditure would override these reductions in SPA, and slow weight regain. This study is a randomized trial in older, obese men and women designed to test the hypothesis that adding a self-regulatory intervention (SRI), focused around self-monitoring of SPA, to a weight loss intervention will result in less weight and fat mass regain following weight loss than a comparable intervention that lacks this self-regulatory behavioral strategy. Participants (n=72) are randomized to a 5-month weight loss intervention with or without the addition of a behavioral component that includes an innovative approach to promoting increased SPA. Both groups then transition to self-selected diet and exercise behavior for a 5-month follow-up. Throughout the 10-month period, the SRI group is provided with an intervention designed to promote a SPA level that is equal to or greater than each individual's baseline SPA level, allowing us to isolate the effects of the SPA self-regulatory intervention component on weight and fat mass regain.
Obesity; Weight loss maintenance; Self-monitoring; Self-regulation; Physical activity
It is unclear whether strength training (ST) or power training (PT) is the more effective intervention at improving muscle strength and power and physical function in older adults. The authors compared the effects of lower extremity PT with those of ST on muscle strength and power in 45 older adults (74.8 ± 5.7 yr) with self-reported difficulty in common daily activities. Participants were randomized to 1 of 3 treatment groups: PT, ST, or wait-list control. PT and ST trained 3 times/wk for 12 wk using knee-extension (KE) and leg-press (LP) machines at ~70% of 1-repetition maximum (1RM). For PT, the concentric phase of the KE and LP was completed “as fast as possible,” whereas for ST the concentric phase was 2–3 s. Both PT and ST paused briefly at the midpoint of the movement and completed the eccentric phase of the movement in 2–3 s. PT and ST groups showed significant improvements in KE and LP 1RM compared with the control group. Maximum KE and LP power increased approximately twofold in PT compared with ST. At 12 wk, compared with control, maximum KE and LP power were significantly increased for the PT group but not for the ST group. In older adults with compromised function, PT leads to similar increases in strength and larger increases in power than ST.
aging; resistance training; disability; physical function
A prospective design was used to examine predictors of adherence to a physical activity intervention in older adults with compromised function.
The sample included 213 men (31.1%) and women (68.9%) with an average age of 76.53 years.
The predictor variables accounted for 10% of the variance in percent attendance during adoption and transition, respectively. Adding percent attendance during adoption to the prediction of percent attendance during transition increased the explained variance in this phase to 21%. During maintenance, the predictors accounted for 13% of the variance in frequency of physical activity; this estimate increased to 46% when adding in percent attendance from the transition phase.
These results are encouraging in that the physical activity intervention appears to have been well tolerated by diverse subgroups of older adults. The role of prior behavior in predicting downstream adherence underscores the importance of developing proactive interventions for treating nonadherence in older adult populations.
Disability; Physical Activity; Older Adults; Adherence
In older adults reduced mobility is common and is an independent risk factor for morbidity, hospitalization, disability, and mortality. Limited evidence suggests that physical activity may help prevent mobility disability; however, there are no definitive clinical trials examining if physical activity prevents or delays mobility disability.
To test the hypothesis that a long-term structured physical activity program is more effective than a health education program (also referred to as a successful aging program) in reducing the risk of major mobility disability.
Design, Setting, and Participants
The Lifestyle Interventions and Independence for Elders (LIFE) study was a multicenter, randomized trial that enrolled participants between February 2010 and December 2011, who participated for an average of 2.6 years. Follow-up ended in December 2013. Outcome assessors were blinded to the intervention assignment. Participants were recruited from urban, suburban and rural communities at 8 field centers throughout the US. We randomized a volunteer sample of 1,635 sedentary men and women aged 70–89 years who had physical limitations, defined as a score on the Short Physical Performance Battery of 9 or below, but were able to walk 400 m.
Participants were randomized to a structured moderate intensity physical activity program (n=818) done in a center and at home that included including aerobic, resistance and flexibility training activities or to a health education program (n=817) consisting of workshops on topics relevant to older adults and upper extremity stretching exercises.
Main Outcomes and Measures
The primary outcome was major mobility disability objectively defined by loss of ability to walk 400 m.
Incident major mobility disability occurred in 30.1% (n=246/818) of physical activity and 35.5% (n=290/817) of health education participants (HR=0.82, 95%CI=0.69–0.98, p=0.03). Persistent mobility disability was experienced by 120/818 (14.7%) physical activity and 162/817 (19.8%) health education participants (HR=0.72; 95%CI=0.57–0.91; p=0.006). Serious adverse events were reported by 404/818 (49.4%) of the physical activity and 373/817 (45.7%) of the health education participants (Risk Ratio=1.08; 95%CI=0.98–1.20).
Conclusions and Relevance
A structured moderate intensity physical activity program, compared with a health education program, reduced major mobility disability over 2.6 years among older adults at risk of disability. These findings suggest mobility benefit from such a program in vulnerable older adults.
ClinicalsTrials.gov identifier NCT01072500.
A complication of cardiovascular disease (CVD) and the metabolic syndrome (MetS) among older adults is loss of mobility. The American Heart Association has identified weight management as a core component of secondary prevention programs for CVD and is an important risk factor for physical disability. The American Society for Nutrition and the Obesity Society have highlighted the need for long-term randomized clinical trials to evaluate the independent and additive effects of diet-induced weight loss (WL) and physical activity in older persons on outcomes such as mobility, muscle function, and obesity related diseases.
Here we describe the rationale, design, and methods of a translational study, the Cooperative Lifestyle Intervention Program-II (CLIP-II).
CLIP-II will randomize 252 obese, older adults with CVD or MetS to a weight loss only treatment (WL), aerobic exercise training (AT)+WL, or resistance exercise training (RT)+WL for 18 months. The dual primary outcomes are mobility and knee extensor strength. The interventions will be delivered by YMCA community partners with our staff as trainers and advisers. This study will provide the first large scale trial to evaluate the effects of diet-induced WL on mobility in obese, older adults with CVD or MetS as compared to WL combined with two different modes of physical activity (AT and RT). Because uncertainty exists about the best approach for promoting WL in older adults due to concerns with the loss of lean mass, the design also permits a contrast between AT+WL and RT+WL on muscle strength.
translational science; exercise; older adults; obesity; weight loss; physical activity
To compare the relative effects of four years of intensive lifestyle intervention on weight, fitness, and cardiovascular disease risk factors among older versus younger individuals
A randomized controlled clinical trial
16 US clinical sites
Individuals with type 2 diabetes: 1,053 aged 65–76 years and 4,092 aged 45–64 years
An intensive behavioral intervention designed to promote and maintain weight loss through caloric restriction and increased physical activity compared to a condition of diabetes support and education.
Standardized assessments of weight, fitness (based on graded exercise testing), and cardiovascular disease risk factors
Across four years, older individuals had greater intervention-related mean weight losses than younger participants, 6.2% versus 5.1% (interaction p=0.006) and comparable relative mean increases in fitness, 0.56 versus 0.53 metabolic equivalents (interaction p=0.72). These benefits were seen consistently across subgroups of older adults formed by many demographic and health factors. Among a panel of age-related health conditions, only self-reported worsening vision was associated with poorer intervention-related weight loss in older individuals. The intensive lifestyle intervention produced mean increases in high density lipoprotein cholesterol (2.03 mg/dl; p<0.001) and decreases in glycated hemoglobin (0.21%; p<0.001) and waist girth (3.52 cc; p<0.001) across 4 years that were at least as large in older compared to younger individuals.
Intensive lifestyle intervention targeting weight loss and increased physical activity is effective in overweight and obese older individuals to produce sustained weight loss and improvements in fitness and cardiovascular risk factors.
Behavioral intervention; Weight loss; Physical activity; Type 2 diabetes mellitus; Cardiovascular disease risk factors
Our primary objective was to determine the long-term effects of physical activity (PA) and weight loss (WL) on body composition in overweight/obese older adults. Secondarily, we evaluated the association between change in body mass and composition on change in several cardiometabolic risk factors and mobility.
Design and Methods
288 older (X±SD: 67.0±4.8 years), overweight/obese (BMI 32.8±3.8 kg/m2) men and women participated in this 18 month randomized, controlled trial. Treatment groups included PA+WL (n=98), PA-only (n=97), and a successful aging (SA) health education control (n=93). DXA-acquired body composition measures (total body fat and lean mass), conventional biomarkers of cardiometabolic risk, and 400-m walk time were obtained at baseline and 18 months.
Fat mass was significantly reduced from (X±SE) 36.5±8.9 kg to 31.7±9.0 kg in the PA+WL group (p<0.01), but remained unchanged from baseline in the PA-only (−0.8±3.8 kg) and SA (−0.0±3.9 kg) groups. Lean mass losses were three times greater in the PA+WL group compared to PA-only or SA groups (−2.5±2.8 kg vs. −0.7±2.2 kg or −0.8±2.4 kg, respectively; p<0.01); yet due to a larger decrease in fat mass, percent lean mass was significantly increased over baseline in the PA+WL group (2.1%±2.6%; p<0.01). Fat mass loss was primarily responsible for WL-associated improvements in cardiometabolic risk factors, while reduction in body weight, regardless of compartment, was significantly associated with improved mobility.
This 18 month PA+WL program resulted in a significant reduction in percent body fat with a concomitant increase in percent body lean mass. Shifts in body weight and composition were associated with favorable changes in clinical parameters of cardiometabolic risk and mobility. Moderate PA without WL had no effect on body composition.
weight loss; physical activity; body composition; cardiometabolic risk; functional decline; aging
To determine the independent effect of long-term physical activity (PA) and the combined effects of long-term PA and weight loss (WL) on inflammation in overweight and obese older adults.
18-month randomized, controlled trial.
This study was conducted within the community infrastructure of Cooperative Extension Centers.
288 older (60–79 years), overweight and obese (BMI > 28 kg/m2) community dwelling men and women at risk for cardiovascular disease (CVD).
PA + WL (n=98), PA only (n=97), or successful aging (SA) health education (n=93) intervention.
Biomarkers of inflammation (adiponectin, leptin, hsIL-6, IL-6sR, IL-8, and sTNFR1) were measured at baseline, 6 and 18 months.
After adjustment for baseline biomarker, wave, gender and visit, both leptin and hsIL-6 showed a significant intervention effect. Specifically, leptin (ng/ml) was significantly lower in the PA+WL group compared to PA or SA [21.3 (95% CI: 19.7–22.9) vs. 29.3 (26.9–31.8) and 30.3 (27.9–32.8), respectively; both p<0.01], and hsIL-6 (pg/mL) was also significantly lower in the PA+WL group compared to PA or SA [2.1 (95% CI: 1.9–2.3) vs. 2.5 (2.3–2.7) and 2.4 (2.2–2.6), respectively; both p<0.05].
Addition of dietary-induced WL to PA reduced leptin and hsIL-6 compared to PA alone and to a SA intervention in older adults at risk for CVD. Results suggest that WL, rather than increased PA, is the lifestyle factor primarily responsible for improvement in the inflammatory profile.
physical activity; weight loss; inflammation; aging
At both the individual and societal levels, the health and economic burden of disability in older adults is enormous in developed countries, including the U.S. Recent studies have revealed that the disablement process in older adults often comprises episodic periods of impaired functioning and periods that are relatively free of disability, amid a secular and natural trend of decline in functioning. Rather than an irreversible, progressive event that is analogous to a chronic disease, disability is better conceptualized and mathematically modeled as states that do not necessarily follow a strict linear order of good-to-bad. Statistical tools, including Markov models, which allow bidirectional transition between states, and random effects models, which allow individual-specific rate of secular decline, are pertinent. In this paper, we propose a mixed effects, multivariate, hidden Markov model to handle partially ordered disability states. The model generalizes the continuation ratio model for ordinal data in the generalized linear model literature and provides a formal framework for testing the effects of risk factors and/or an intervention on the transitions between different disability states. Under a generalization of the proportional odds ratio assumption, the proposed model circumvents the problem of a potentially large number of parameters when the number of states and the number of covariates are substantial. We describe a maximum likelihood method for estimating the partially ordered, mixed effects model and show how the model can be applied to a longitudinal data set that consists of N = 2,903 older adults followed for 10 years in the Health Aging and Body Composition Study. We further statistically test the effects of various risk factors upon the probabilities of transition into various severe disability states. The result can be used to inform geriatric and public health science researchers who study the disablement process.
Latent Markov model; continuation ratio model; EM algorithm; generalized linear model; Health ABC study
We studied whether a 6‐month group‐mediated cognitive behavioral (GMCB) intervention for peripheral artery disease (PAD) participants, which promoted home‐based walking exercise, improved 6‐minute walk and other outcomes at 12‐month follow‐up, 6 months after completing the intervention, compared to a control group.
Methods and Results
We randomized PAD participants to a GMCB intervention or a control group. During phase I (months 1 to 6), the intervention used group support and self‐regulatory skills during weekly on‐site meetings to help participants adhere to home‐based exercise. The control group received weekly on‐site lectures on topics unrelated to exercise. Primary outcomes were measured at the end of phase I. During phase II (months 7 to 12), each group received telephone contact. Compared to controls, participants randomized to the intervention increased their 6‐minute walk distance from baseline to 12‐month follow‐up, (from 355.4 to 381.9 m in the intervention versus 353.1 to 345.6 m in the control group; mean difference=+34.1 m; 95% confidence interval [CI]=+14.6, +53.5; P<0.001) and their Walking Impairment Questionnaire (WIQ) speed score (from 36.1 to 46.5 in the intervention group versus 34.9 to 36.5 in the control group; mean difference =+8.8; 95% CI=+1.6, +16.1; P=0.018). Change in the WIQ distance score was not different between the 2 groups at 12‐month follow‐up (P=0.139).
A weekly on‐site GMCB intervention that promoted home‐based walking exercise intervention for people with PAD demonstrated continued benefit at 12‐month follow‐up, 6 months after the GMCB intervention was completed.
Clinical Trial Registration
URL: ClinicalTrials.gov. Unique identifier: NCT00693940.
behavior change; exercise; mobility; peripheral artery disease; physical functioning
Knee osteoarthritis (OA) is a leading cause of functional disability among American adults. Obesity is a strong independent risk factor for OA. While research emphasizes the role of obesity in the OA-physical function relationship, the extent to which weight status impacts salient physical, health, and pain measures in older, knee OA patients is not well delineated. The primary aim of this study was to assess differences in mobility performance (stair climb and 400-meter walk), mobility-related self-efficacy, pain symptoms (WOMAC), and measures of accelerometer-determined physical activity (PA) as a function of weight status. Analysis of covariance was conducted to examine differences on the dependent variables. Obese class III patients were outperformed by their counterparts on nearly every measure of mobility, mobility-related self-efficacy, and the assessment of pain symptoms. These outcomes did not differ among other weight comparisons. Normal weight subjects outperformed classes I, II, and III counterparts on most measures of PA (engagement in moderate or greater PA and total weekly steps). Additionally, overweight participants outperformed obese class II participants and obese class I participants outperformed obese classes II and III participants on total weekly steps. Collectively, these findings underscore the meaningful differences observed in relevant OA outcomes as a function of increasing levels of body weight.
Physical activity (PA) appears to have a positive effect on physical function, however, studies have not examined multiple indices of physical function jointly nor have they conceptualized physical functioning as a state rather than a trait.
About 424 men and women aged 70–89 were randomly assigned to complete a PA or a successful aging (SA) education program. Balance, gait speed, chair stand performance, grip strength, and time to complete the 400-m walk were assessed at baseline and at 6 and 12 months. Using hidden Markov model, empiric states of physical functioning were derived based on these performance measures of balance, strength, and mobility. Rates of gain and loss in physical function were compared between PA and SA.
Eight states of disability were identified and condensed into four clinically relevant states. State 1 represented mild disability with physical functioning, states 2 and 3 were considered intermediate states of disability, and state 4 severe disability. About 30.1% of all participants changed states at 6 months, 24.1% at 12 months, and 11.0% at both time points. The PA group was more likely to regain or sustain functioning and less likely to lose functioning when compared with SA. For example, PA participants were 20% more likely than the SA participants to remain in state 1.
PA appears to have a favorable effect on the dynamics of physical functioning in older adults.
Older adults; Physical activity; Randomized controlled trial; Physical functioning; Transitional states.
There is a growing awareness in the field of neuroscience that the self-regulation of eating behavior is driven by complex networks within the brain. These networks may be vulnerable to “hot states” which people can move into and out of dynamically throughout the course of a day as a function of changes in affect or visceral cues. The goal of the current study was to identify and determine differences in the Hot-state Brain Network of Appetite (HBN-A) that exists after a brief period of food restraint followed either by the consumption of a meal replacement (MR) or water. Fourteen overweight/obese adults came to our laboratory on two different occasions. Both times they consumed a controlled breakfast meal and then were restricted from eating for 2.5 h prior to an MRI scan. On one visit, they consumed a meal replacement (MR) liquid meal after this period of food restriction; on the other visit they consumed an equal amount of water. After these manipulations, the participants underwent a resting fMRI scan. Our first study aim employed an exploratory, data-driven approach to identify hubs relevant to the HBN-A. Using data from the water condition, five regions were found to be the hubs or nodes of the HBN-A: insula, anterior cingulated cortex, the superior temporal pole, the amygdala, and the hippocampus. We then demonstrated that the consumption of a liquid MR dampened interconnectivity between the nodes of the HBN-A as compared to water. Importantly and consistent with these network data, the consumption of a MR beverage also lowered state cravings and hunger.
meal replacement; craving; eating behavior; obesity; brain networks; graph-theory