Andrea C. Buchholz

The validity of bioelectrical impedance models in clinical populations

Bioelectrical impedance analysis (BIA) is the most commonly used body composition technique in published studies. Herein we review the theory and assumptions underlying the various BIA and bioelectrical impedance spectroscopy (BIS) models, because these assumptions may be invalidated in clinical populations. Single-frequency serial BIA and discrete multifrequency BIA may be of limited validity in populations other than healthy, young, euvolemic adults. Both models inaccurately predict total body water (TBW) and extracellular water (ECW) in populations with changes in trunk geometry or fluid compartmentalization, especially at the level of the individual. Single-frequency parallel BIA may predict body composition with greater accuracy than the serial model. Hand-to-hand and leg-to-leg BIA models do not accurately predict percent fat mass. BIS may predict ECW, but not TBW, more accurately than single-frequency BIA. Segmental BIS appears to be sensitive to fluid accumulation in the trunk. In general, bioelectrical impedance technology may be acceptable for determining body composition of groups and for monitoring changes in body composition within individuals over time. Use of the technology to make single measurements in individual patients, however, is not recommended. This has implications in clinical settings, in which measurement of individual patients is important.

Leisure time physical activity in a population-based sample of people with spinal cord injury part I: demographic and injury-related correlates.

OBJECTIVES To estimate the number of minutes a day of leisure time physical activity (LTPA) performed by people with chronic spinal cord injury (SCI) and to identify the demographic and injury-related characteristics associated with LTPA in a population-based sample of people with chronic SCI. DESIGN Cross-sectional telephone survey. SETTING General community. PARTICIPANTS Men and women with SCI (N=695). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES The number of minutes/day of LTPA performed at a mild intensity or greater. RESULTS Respondents reported mean minutes +/- SD of 27.14+/-49.36 of LTPA/d; however, 50% reported no LTPA whatsoever. In a multiple regression analysis, sex, age, years postinjury, injury severity, and primary mode of mobility each emerged as a unique predictor of LTPA. Multiple correspondence analysis indicated that being a man over the age of 34 years and greater than 11 years postinjury was associated with inactivity, while being a manual wheelchair user and having motor complete paraplegia were associated with the highest level of daily LTPA. CONCLUSIONS Daily LTPA levels are generally low in people with SCI. Women, older adults, people with less recent injuries, people with more severe injuries, and users of power wheelchairs and gait aids are general subgroups that may require special attention and resources to overcome unique barriers to LTPA. Specific subgroups may also require targeted interventions.

Energy expenditure in chronic spinal cord injury.

Purpose of reviewObesity is a common secondary complication of chronic spinal cord injury and is associated with adverse metabolic sequelae. Because positive energy balance is the fundamental cause of obesity, we herein review the current knowledge pertaining to total daily energy expenditure, including resting metabolic rate, the thermic effect of food, and physical activity, in the spinal cord injury population. Recent findingsCommonly used equations to predict resting metabolic rate overestimate measured requirements in chronic spinal cord injury by 5-32%. Measured resting metabolic rate is 14-27% lower in persons with spinal cord injury versus those without, due to decreased fat-free mass and sympathetic nervous system activity in this population. However, preliminary evidence suggests that neither the metabolic activity of the fat-free body, nor the obligatory phase of the thermic effect of food is different between those with and without injury. Physical activity levels, especially in those with tetraplegia and complete lesions, are lower than recommended or lower than those of able-bodied persons. SummaryNew equations to predict resting metabolic rate should be validated and prospectively tested in a large sample of men and women with complete and incomplete paraplegia and tetraplegia. Whether the facultative phase of the thermic effect of food is different between those with and without SCI remains to be elucidated. Persons with chronic spinal cord injury, and perhaps those with tetraplegia and complete lesions especially, should be encouraged to engage in increased frequency, intensity and/or duration of physical activity. Future research efforts should explore the effects of level and completeness of neurological lesion on resting metabolic rate, thermic effect of food, and physical activity.

Lowering body mass index cutoffs better identifies obese persons with spinal cord injury.

Study design:Cross-sectional, non-experimental design.Objectives:(1) Determine the sensitivity and specificity of the general population body mass index (BMI) cutoff for obesity (30 kg m−2) in a representative sample of persons with spinal cord injury (SCI); (2) develop a more sensitive BMI cutoff for obesity based on percentage of fat mass (%FM) and C-reactive protein (CRP).Setting:Ontario, Canada.Methods:A total of 77 community-dwelling adults with chronic SCI underwent anthropometric measures (%FM by bioelectrical impedance analysis, length, weight, BMI (kg m−2)) and provided blood samples to determine CRP. Sensitivity and specificity analyses, piecewise regression, non-linear regression, and receiver–operator characteristic curves were used to determine new BMI cutoffs.Results:A BMI cutoff of 30 kg m−2 failed to identify 73.9% of obese participants vs 26.1% at a lowered cutoff of 25 kg m−2. BMI cutoffs based on risk levels of the %FM and CRP considered together ranged from 22.1 kg m−2–26.5 kg m−2.Conclusions:People with chronic SCI and BMI values >22 kg m−2 should be considered as being at high risk for obesity and obesity-related chronic diseases.Sponsorship:Canadian Institutes of Health Research.

Greater daily leisure time physical activity is associated with lower chronic disease risk in adults with spinal cord injury

The objective of this study was to examine the relationship between leisure time physical activity (LTPA) and common risk factors for cardiovascular disease (CVD) and type 2 diabetes in community-dwelling adults with chronic spinal cord injury (SCI). LTPA was measured using the Physical Activity Recall Assessment for People with SCI in 76 men and women with chronic (> or =1 year) paraplegia or tetraplegia, living in or near Hamilton, Ontario. Body mass index (BMI), waist circumference, body composition (fat mass (FM) and fat-free mass (FFM)), blood pressure, and biochemical data were collected. Thirty-seven percent (n = 28 participants) were inactive, reporting no LTPA whatsoever, and were compared with an equal-sized group consisting of the most active study participants (> or =25 min of LTPA per day). After adjusting for significant covariates, BMI (18.7%), %FM (19.4%), and C-reactive protein (143%) were all lower, and %FFM was higher (7.2%), in active participants (all p < or = 0.05). Ten percent of active participants vs. 33% of inactive participants were insulin resistant (p = 0.03). Waist circumference (17.6%) and systolic blood pressure (15.3%) were lower in active vs. inactive participants with paraplegia (both p < or = 0.05), but not tetraplegia. In conclusion, greater daily LTPA is associated with lower levels of selected CVD and type 2 diabetes risk factors in individuals living with SCI. Whether this relationship translates into a lower incidence of these chronic diseases has yet to be determined.

Inflammation, obesity, and fatty acid metabolism: influence of n-3 polyunsaturated fatty acids on factors contributing to metabolic syndrome

Metabolic syndrome (MetS) comprises an array of metabolic risk factors including abdominal obesity, dyslipidemia, hypertension, and glucose intolerance. Individuals with MetS are at elevated risk for diabetes and cardiovascular disease. Central to the etiology of MetS is an interrelated triad comprising inflammation, abdominal obesity, and aberrations in fatty acid metabolism, coupled with the more recently recognized changes in metabolism during the postprandial period. We review herein preliminary evidence regarding the role of dietary n-3 polyunsaturated fatty acids in modulating each of the components of the triad of adiposity, inflammation, and fatty acid metabolism, with particular attention to the role of the postprandial period as a contributor to the pathophysiology of MetS.

Establishing evidence-based physical activity guidelines: methods for the Study of Health and Activity in People with Spinal Cord Injury (SHAPE SCI)

Study design:Prospective, observational cohort study.Objectives:This paper describes the rationale and methodology for the Study of Health and Activity in People with Spinal Cord Injury (SHAPE SCI). The study aims to (1) describe physical activity levels of people with different injury levels and completeness, (2) examine the relationship between physical activity, risk and/or presence of secondary health complications and risk of chronic disease, and (3) identify determinants of physical activity in the SCI population.Setting:Ontario, Canada.Methods:Seven hundred and twenty men and women who have incurred a traumatic SCI complete self-report measures of physical activity, physical activity determinants, secondary health problems and subjective well-being during a telephone interview. A representative subsample (n=81) participate in chronic disease risk factor testing for obesity, insulin resistance and coronary heart disease. Measures are taken at baseline, 6 and 18 months.Conclusion:SHAPE SCI will provide much-needed epidemiological information on physical activity patterns, determinants and health in people with SCI. This information will provide a foundation for the establishment of evidence-based physical activity guidelines and interventions tailored to the SCI community.

Leisure Time Physical Activity in a Population-Based Sample of People With Spinal Cord Injury Part II: Activity Types, Intensities, and Durations

OBJECTIVE To describe the types, intensities, and average duration of leisure time physical activities (LTPAs) performed by people with chronic spinal cord injury (SCI). DESIGN Cross-sectional telephone survey. SETTING General community. PARTICIPANTS Men and women with SCI (N=347) who reported engaging in LTPA over the previous 3 days. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Mean minutes a day of LTPA performed at mild, moderate, and heavy intensities; proportion of respondents performing specific types of LTPA. RESULTS Participants reported a mean +/- SD of 55.15+/-59.05min/d of LTPA at a mild intensity or greater. Median LTPA was 33.33min/d. More activity was done at a moderate intensity (mean +/- SD, 25.49+/-42.11min/d) than mild (mean +/- SD, 19.14+/-37.77min/d) or heavy intensities (mean +/- SD, 10.52+/-22.17min/d). Most participants reported mild (54%) or moderate intensity LTPA (68%), while a minority reported heavy intensity LTPA (43%). The 3 most frequently reported types of LTPA were resistance training (33%), aerobic exercise (25%), and wheeling (24%). Craftsmanship (mean +/- SD, 83.79+/-96.00min/d) and sports activities (mean +/- SD, 60.86+/-59.76 min/d) were performed for the longest durations. CONCLUSIONS There is considerable variability in daily LTPA among active people with SCI and variability across different types of LTPA in terms of typical durations and intensities. This information can be used to help people with chronic SCI become more active by highlighting activities that meet individual abilities, needs, and desires.

C-Reactive protein in adults with chronic spinal cord injury: increased chronic inflammation in tetraplegia vs paraplegia.

Study design:Cross-sectional.Objectives:In community-dwelling adults with chronic spinal cord injury (SCI), to (1) quantify C-reactive protein (CRP), a marker of inflammation and cardiovascular disease (CVD) risk; (2) determine factors associated with CRP.Setting:Hamilton, Ontario, Canada.Methods:We examined CVD risk factors in 69 participants. Measurements included length, weight, waist circumference, blood pressure, percent fat mass (bioelectrical impedance analysis) and fasting blood parameters (high-sensitivity CRP, lipids, insulin, glucose, insulin resistance by homeostasis model assessment (HOMA)).Results:Mean CRP of the group was 3.37±2.86 mg−l−1, consistent with the American Heart Association (AHA) definition of high risk of CVD. CRP was 74% higher in persons with tetraplegia (4.31±2.97) than those with paraplegia (2.47±2.47 mg l−1, P=0.002), consistent with high CVD risk. Participants with high CRP (3.1–9.9 mg l−1) had greater waist circumference, BMI, percent fat mass and HOMA values than those with lower CRP (⩽3.0 mg l−1, all P<0.05). LogCRP was independently correlated with waist circumference (r=0.612), logTriglycerides (r=0.342), logInsulin (r=0.309) and logHOMA (r=0.316, all P<0.05). Only level of lesion and waist circumference remained significantly associated with logCRP when variables with significant bivariate correlations were included in multiple regression analysis.Conclusion:Mean CRP values in this sample of adults with chronic SCI were consistent with the AHA classification of high CVD risk, especially those of persons with tetraplegia. Level of lesion and waist circumference are independently associated with CRP in this population.

Evidence of dietary inadequacy in adults with chronic spinal cord injury

Study design:Cross-sectional, observational study.Objective:Estimate prevalence of inadequate dietary intakes in community-dwelling men and women with chronic spinal cord injury (SCI).Setting:Ontario, Canada.Methods:In-home interviewer administered multiple-pass 24-h recalls were collected at baseline (n=77) and at 6 months (n=68). Dietary intake (adjusted to remove intra-individual variation) was compared with the dietary reference intakes (DRIs), specifically the estimated average requirement, adequate intake (AI) and acceptable macronutrient distribution ranges (AMDR).Results:Macronutrient intakes, as percentages of daily energy, for men (16% protein, 52% carbohydrate, 30% fat) and women (17% protein, 53% carbohydrate, 28% fat) were within the AMDR. Despite this, inadequate intakes for men (n=63) and women (n=14) were determined for vitamin A (92 and 57%), magnesium (89 and 71%), folate (75 and 79%), zinc (71 and 29%), vitamin C (52 and 14%), thiamine (22 and 14%), vitamin B12 (6 and 29%), riboflavin (5% men) and vitamin B6 (24% men). Mean usual intakes of fiber, vitamin D, calcium and potassium fell below the AI for men and women. In all, 53% of participants consumed a micronutrient supplement in the previous 24 h at baseline and at 6 months—specifically, calcium (29, 19%), multivitamin (26, 25%), vitamin D (22, 12%) and vitamin C (9, 6%).Conclusion:Our results show numerous nutrient inadequacies, relative to the DRIs, for men and women with SCI. This study has important implications for clinical dietetic practice in the SCI population.Sponsorship:Canadian Institutes of Health Research.