Brittney S. Lange-Maia

Predicting human movement with multiple accelerometers using movelets.

PURPOSE The study aims were 1) to develop transparent algorithms that use short segments of training data for predicting activity types and 2) to compare the prediction performance of the proposed algorithms using single accelerometers and multiple accelerometers. METHODS Sixteen participants (age, 80.6 yr (4.8 yr); body mass index, 26.1 kg·m (2.5 kg·m)) performed 15 lifestyle activities in the laboratory, each wearing three accelerometers at the right hip and left and right wrists. Triaxial accelerometry data were collected at 80 Hz using ActiGraph GT3X+. Prediction algorithms were developed, which, instead of extracting features, build activity-specific dictionaries composed of short signal segments called movelets. Three alternative approaches were proposed to integrate the information from the multiple accelerometers. RESULTS With at most several seconds of training data per activity, the prediction accuracy at the second-level temporal resolution was very high for lying, standing, normal/fast walking, and standing up from a chair (the median prediction accuracy ranged from 88.2% to 99.9% on the basis of the single-accelerometer movelet approach). For these activities, wrist-worn accelerometers performed almost as well as hip-worn accelerometers (the median difference in accuracy between wrist and hip ranged from -2.7% to 5.8%). Modest improvements in prediction accuracy were achieved by integrating information from multiple accelerometers. DISCUSSION AND CONCLUSIONS It is possible to achieve high prediction accuracy at the second-level temporal resolution with very limited training data. To increase prediction accuracy from the simultaneous use of multiple accelerometers, a careful selection of integrative approaches is required.

Physical Activity and Change in Long Distance Corridor Walk Performance in the Health, Aging, and Body Composition Study

To examine the prospective relationship between self‐reported physical activity and aerobic fitness in the Health, Aging, and Body Composition Study (Health ABC) using the Long Distance Corridor Walk (LDCW).

Movement prediction using accelerometers in a human population

We introduce statistical methods for predicting the types of human activity at sub-second resolution using triaxial accelerometry data. The major innovation is that we use labeled activity data from some subjects to predict the activity labels of other subjects. To achieve this, we normalize the data across subjects by matching the standing up and lying down portions of triaxial accelerometry data. This is necessary to account for differences between the variability in the position of the device relative to gravity, which are induced by body shape and size as well as by the ambiguous definition of device placement. We also normalize the data at the device level to ensure that the magnitude of the signal at rest is similar across devices. After normalization we use overlapping movelets (segments of triaxial accelerometry time series) extracted from some of the subjects to predict the movement type of the other subjects. The problem was motivated by and is applied to a laboratory study of 20 older participants who performed different activities while wearing accelerometers at the hip. Prediction results based on other peoples labeled dictionaries of activity performed almost as well as those obtained using their own labeled dictionaries. These findings indicate that prediction of activity types for data collected during natural activities of daily living may actually be possible.

Sensorimotor Peripheral Nerve Function and the Longitudinal Relationship With Endurance Walking in the Health, Aging and Body Composition Study

OBJECTIVES To determine whether lower extremity sensorimotor peripheral nerve deficits are associated with reduced walking endurance in older adults. DESIGN Prospective cohort study with 6 years of follow-up. SETTING Two university research clinics. PARTICIPANTS Community-dwelling older adults enrolled in the Health, Aging and Body Composition Study from the 2000-2001 annual clinical examination (N=2393; mean age ± SD, 76.5±2.9y; 48.2% men; 38.2% black) and a subset with longitudinal data (n=1178). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Participants underwent peripheral nerve function examination in 2000-2001, including peroneal motor nerve conduction amplitude and velocity, vibration perception threshold, and monofilament testing. Symptoms of lower extremity peripheral neuropathy included numbness or tingling and sudden stabbing, burning, pain, or aches in the feet or legs. The Long Distance Corridor Walk (LDCW) (400 m) was administered in 2000-2001 and every 2 years afterward for 6 years to assess endurance walking performance over time. RESULTS In separate, fully adjusted linear mixed models, poor vibration threshold (>130 μm), 10-g and 1.4-g monofilament insensitivity were each associated with a slower 400-m walk completion time (16.0 s, 14.4s, and 6.9 s slower, respectively; P<.05 for each). Poor motor amplitude (<1 mV), poor vibration perception threshold, and 10-g monofilament insensitivity were related to greater slowing per year (4.7, 4.2, and 3.8 additional seconds per year, respectively; P<.05), although poor motor amplitude was not associated with initial completion time. CONCLUSIONS Poorer sensorimotor peripheral nerve function is related to slower endurance walking and greater slowing longitudinally. Interventions to reduce the burden of sensorimotor peripheral nerve function impairments should be considered to help older adults maintain walking endurance-a critical component for remaining independent in the community.

Relationship between sensorimotor peripheral nerve function and indicators of cardiovascular autonomic function in older adults from the Health, Aging and Body composition Study

Background Age‐related peripheral nervous system (PNS) impairments are highly prevalent in older adults. Although sensorimotor and cardiovascular autonomic function have been shown to be related in persons with diabetes, the nature of the relationship in general community‐dwelling older adult populations is unknown. Methods Health, Aging and Body Composition participants (n = 2399, age = 76.5 ± 2.9 years, 52% women, 38% black) underwent peripheral nerve testing at the 2000/01 clinic visit. Nerve conduction amplitude and velocity were measured at the peroneal motor nerve. Sensory nerve function was assessed with vibration detection threshold and monofilament (1.4‐g/10‐g) testing at the big toe. Symptoms of lower‐extremity peripheral neuropathy were collected by self‐report. Cardiovascular autonomic function indicators included postural hypotension, resting heart rate (HR), as well as HR response to and recovery from submaximal exercise testing (400 m walk). Multivariable modeling adjusted for demographic/lifestyle factors, medication use and comorbid conditions. Results In fully adjusted models, poor motor nerve conduction velocity (<40 m/s) was associated with greater odds of postural hypotension, (OR = 1.6, 95% CI: 1.0–2.5), while poor motor amplitude (<1 mV) was associated with 2.3 beats/min (p = 0.003) higher resting HR. No associations were observed between sensory nerve function or symptoms of peripheral neuropathy and indicators of cardiovascular autonomic function. Conclusions Motor nerve function and indicators of cardiovascular autonomic function remained significantly related even after considering many potentially shared risk factors. Future studies should investigate common underlying processes for developing multiple PNS impairments in older adults.

Physical Activity and Physical Function: Moving and Aging

Evidence supports that the physical disablement process starts earlier than previously thought, in midlife when women still have many years to live. Physical activity participation and interventions have been successful in preventing disability in older adults and may be promising for maintaining function at younger ages. Changing the conversation to more relevant topics in midlife, like positive changes in body composition, sleep, and improved mood, may move the dial on participation, as midlife women do not meet guidelines for physical activity. Exploring the role of reproductive aging beyond chronologic aging may provide gender-specific insights on both disablement and participation.

Chronic kidney disease and peripheral nerve function in the Health, Aging and Body Composition Study

BACKGROUND Chronic kidney disease (CKD) is associated with poor mobility. Peripheral nerve function alterations play a significant role in low mobility. We tested the hypothesis that early CKD is associated with altered sensory, motor and autonomic nerve function. METHODS Participants in the Health, Aging and Body Composition cohort who had kidney function measures in Year 3 (1999-2000) and nerve function measurements at Year 4 (2000-01) were analyzed (n = 2290). Sensory (vibration threshold, monofilament insensitivity to light and standard touch), motor [compound motor action potentials (CMAPs), nerve conduction velocities (NCVs)] and autonomic (heart rate response and recovery after a 400-m walk test) nerve function as well as participant characteristics were compared across cystatin C- and creatinine-based estimated glomerular filtration rate categorized as ≤60 (CKD) or >60 mL/min/1.73 m2 (non-CKD). The association between CKD and nerve function was examined with logistic regression adjusted for covariates. RESULTS Participants with CKD (n = 476) were older (77 ± 3 versus 75 ± 3 years; P < 0.05) and had a higher prevalence of diabetes (20.6% versus 13.1%; P < 0.001). CKD was associated with higher odds for vibration detection threshold {odds ratio [OR] 1.7 [95% confidence interval (CI) 1.1-2.7]} and light touch insensitivity [OR 1.4 (95% CI 1.1-1.7)]. CMAPs and NCVs were not significantly different between CKD and non-CKD patients. In adjusted analyses, participants with CKD had higher odds of an abnormal heart rate response [OR 1.6 (95% CI 1.1-2.2)] and poor heart rate recovery [OR 1.5 (95% CI 1.1-2.0)]. CONCLUSIONS CKD is associated with changes in sensory and autonomic nerve function, even after adjustment for demographics and comorbidities, including diabetes. Longitudinal studies in CKD are needed to determine the contribution of nerve impairments to clinically important outcomes.

Association of community-level inequities and premature mortality: Chicago, 2011–2015

Background Substantial disparities in life expectancy exist between Chicago’s 77 defined community areas, ranging from approximately 69 to 85 years. Prior work in New York City and Boston has shown that community-level racial and economic segregation as measured by the Index of Concentration at the Extremes (ICE) is strongly related to premature mortality. This novel metric allows for the joint assessment of area-based income and racial polarisation. This study aimed to assess the relationships between racial and economic segregation and economic hardship with premature mortality in Chicago. Methods Annual age-adjusted premature mortality rates (deaths <65 years) from 2011 to 2015 were calculated for Chicago’s 77 community areas. ICE measures for household income (<US

A Multimethod Investigation Into Physical Activity in Midlife Women

25 000 vs ≥US

Design of a lifestyle intervention to slow menopause-related progression of intra-abdominal adipose tissue in women: The Women in the Southside Health and Fitness (WISHFIT) study

100 000), race (black vs non-Hispanic white), combined ICE measure incorporating income and race, and hardship index were calculated from 2015 American Community Survey 5-year estimates. Results Average annual premature mortality rates ranged from 94 (95% CI 61 to 133) deaths per 100 000 population age <65 to 699 (95% CI 394 to 1089). Compared with the highest ICE quintiles, communities in the lowest quintiles had significantly higher rates of premature mortality (ICEIncomerate ratio (RR)=3.06, 95% CI 2.51 to 3.73; ICERaceRR=3.07, 95% CI 2.62 to 3.58; ICEIncome+RaceRR=3.27, 95% CI 2.84 to 3.77). Similarly, compared with communities in the lowest hardship index quintile, communities in the highest quintile had significantly higher premature mortality rates (RR=2.79, 95% CI 2.18 to 3.57). Conclusions The strong relationships observed between ICE measures and premature mortality—particularly the combined ICE metric encompassing race and income—support the use of ICE in public health monitoring.