145
JEPonline
Prediction of Cardiovascular Disease Risk: Peak Oxygen Consumption in Sedentary Middle-Aged Subjects
Jatuporn Phoemsapthawee1, Nongnuch Settasatian2, Suchart Sirijaichingkul3, Orathai Tunkamnerdthai4,5, Naruemon Leelayuwat4,5
1Department of Sports Science and Health, Faculty of Sports Science, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom, Thailand, 2Department of Clinical Chemistry, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand, 3Department of Clinical Immunology, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand, 4Department of Physiology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand, 5Exercise and Sport Sciences Development and Research Group, Khon Kaen University, Khon Kaen, Thailand
ABSTRACT
Phoemsapthawee J, Settasatian N, Sirijaichingkul S, Tunkamnerdthai O, Leelayuwat N. Prediction of Cardiovascular Disease Risk: Peak Oxygen Consumption in Sedentary Middle-Aged Subjects. JEPonline 2016;19(6):145-155. The purpose of this study was twofold: (a) to determine the relationship between peak oxygen consumption (VO2 peak) and anthropometric measures and plasma lipid profiles; and (b) to develop regression equations to estimate VO2 peak for healthy sedentary middle-aged men and women. A total of 128 healthy sedentary Thai subjects (51 men, 77 women) were recruited. Blood samples were obtained after a 12-hr fast and analyzed for lipid profiles. Anthropometric and body composition parameters were also investigated. Then, every subject underwent maximal exercise testing for determination of VO2 peak. According to being high correlated with VO2 peak, high-density lipoprotein-cholesterol (HDL-C) and waist circumference were used to develop regression equations for the estimation of VO2 peak in the men (r = 0.75, P0.0001) with an overall mean difference of -0.9 mL·kg-1·min-1 with a standard error of estimate of ±4.4 mL·kg-1·mim-1. In women, the results showed a high correlation between VO2 peak and low-density lipoprotein cholesterol (LDL-C) and HDL-C. Both parameters were used to develop regression equations to estimate VO2 peak in the women (r = 0.76, P0.0001) with an overall mean difference of 0.3 mL·kg-1·min-1 and a standard error of the estimate that was ±5.8 mL·kg-1·mim-1. The VO2 peak is predicted reasonably well from the measurements of HDL-C, LDL-C, and waist circumference in the middle-aged population. The predictive regression equation for the estimation of VO2 peak was more accurate when it was applied by gender. However, this equation needs to be verified before it is widely used.
Key Words: Aerobic Capacity, Lipid Profiles, Abdominal Obesity, VO2 peak
INTRODUCTION
Aerobic capacity is determined by maximal oxygen consumption (VO2 max). It is known to be a useful tool to predict prognosis in patients with cardiovascular disease (CVD) and all causes of mortality (14,25). It is also used to evaluate the performance of cardiopulmonary function in response to exercise (12,17,25). Many factors affect an athlete’s or a patient’s aerobic capacity, including age, gender, motivation, fat mass, muscle mass, training status, diseases, disabilities, and the skills of the person doing the testing (20). Although the VO2 max remains the primary method to evaluate physiological status, a real VO2 max is rarely achieved in severely deconditioned subjects, including cardiac patients, elderly patients, and pediatric patients. In addition, at times the exercise protocol can be complicated and life threatening.
Thus, it is safer to develop regression equations for estimating VO2 peak from parameters that are easily measured such as anthropometric and blood parameters in middle-aged population. The equations have been largely developed in Americans and Europeans (3,11,34). No study, however, has been specifically developed for the predictive equations in middle-aged Asians. Ethnicity is demonstrated to be responsible for the difference in aerobic capacity (26,28,30) in many aspects of anthropometry, physiology, habitual dietary intake, and pattern of activity of daily living. For instance, Asians have been shown to have lower body mass index (BMI) for the same age with a lower percentage of body fat (%BF) when compared with Americans and Europeans (32,33). It is more applicable to use the specific equation for Asian individuals in order to predict their aerobic capacities. Therefore, the purpose of this study was to determine the relationship between VO2 peak and anthropometric measures and blood lipid concentrations, as well as to develop regression equations for estimating VO2 peak for healthy sedentary men and women.
METHODS
Subjects
One-hundred and twenty-eight healthy sedentary (51 male and 77 female) subjects with a mean age of 44.7 ± 0.7 yrs (range, 20 to 65 yrs) were enrolled in this study. According to information from a health questionnaire, physical examination, and blood chemistry, the subjects had no underlying CVD, hypertension, diabetes mellitus (DM), orthopedic problems, neuromuscular disorders, liver disease, kidney disease, and apparent infections and did not receive any medicine for dyslipidemia. All subjects were informed verbally and in writing of the experimental protocol and possible risk involved before signing the consent form approved by the Ethical Committee of Khon Kaen University in accordance with the 1964 Declaration of Helsinki and revised in 1983 in order to participate in the experiment.
Procedures
Aerobic Capacity
At pre-test, the subjects were asked to refrain from eating, smoking, and drinking tea, coffee or alcohol for at least 2 hrs before the measurement session. They were also requested not to engage in strenuous exercise for 24 hrs prior to the trial to ensure a consistent baseline activity level. The maximal oxygen consumption tests were performed using a Vmax 22 system (SensorMedics) configured in the breath-by breath mode. The gas analysis system was calibrated before each trial using commercially available precision gases (26% oxygen, 4% carbon dioxide, and balance nitrogen). Expired gases were collected and analyzed with the gas exchange system to determine oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory exchange ratio (RER), and minute ventilation (VE). Each subject performed a continuous 3-min graded exercise protocol beginning with an initial workload of 30 watts for women and 50 watts for men, which was increased 15 watts for women and 20 watts for men on an electrically braked cycle ergometer. Borg scores for dyspnea and leg muscle fatigue were recorded during the test. The VO2 peak of each of the subject was determined when one of the following criteria was achieved when the subject’s: (a) VO2 reached a plateau with an increase in workload; (b) heart rate reached 85% of age-predicted maximum (220-age); (c) respiratory exchange ratio (RER) was ≥1.15; and (d) pedal frequency was <50 rev·min-1.
Anthropometry and Body Composition Measurements
With the subjects in their minimal clothing, height and body mass were measured with a balanced laboratory scale (Detecto, Webb City, MO U.S.A.). BMI was calculated as the ratio of body weight in kilograms to height in meters squared. Percentage of body fat (%BF) was calculated based on the biceps, triceps, subscapular, and suprailiac skinfold thickness measured using a skinfold caliper (British Indicators Ltd, St Albans, Herts, England). The waist circumference (W) was measured midway between the lower rib margin and the iliac crest at the end of inspiration and the hip (H) was measured around the buttocks at the level of maximal dimension in a freestanding position to calculate the waist to hip ratio (WHR).
Blood Chemistry
After the subjects fasted for 12 hrs, blood samples were obtained from a antecubital vein to obtained concentrations of plasma glucose, blood urea nitrogen (BUN), creatinine, uric acid, albumin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total cholesterol (TC), triglycerides (TG), and HDL-C, which were measured using a chemistry analyzer (Beckman Synchron CX4, USA). The subjects’ LDL-C was calculated using the Friedewald equation (LDL-C = TC – HDL-C – 0.20 ´ TG). All the parameters were analyzed by the Faculty of Associated Medical Science laboratory, Khon Kaen University.
Statistical Analyses
All statistics were performed using the Stata® statistical software, version 11.5. Demographic statistics were generated for the variables of interest and expressed as the mean ± SE. Descriptive statistics were used to express the baseline of subject characteristics. Regression techniques were used to explore relationships among the variables under study. Stepwise and maximal Spearman’s rho correlation coefficient (r) improvements were used for identifying variables that would contribute to the prediction of VO2 peak for each sex separately and for the total subjects. If the statistical probability (P value) was less than 0.05, the differences were considered to be statistical significance.
RESULTS
Combined data on the healthy sedentary Thai individuals showed that men were statistically older and had different results for TG, TG/HDL-C, fasting glucose, height, BM, BMI, %BF, FM, FFM, W, H, W/H ratio, SBP, DBP, MAP, HR, peak HR, and HRR than women (Table 1). There were no significant differences in TC, LDL-C, HDL-C, and VO2 peak between genders.
Table 1. Characteristics of the Subjects.
Total(N = 128) / Men
(N = 51) / Women
(N = 77)
Age (yr) / 44.7 ± 0.7 / 47.9 ± 1.2 / 42.6 ± 0.9**
BM (kg) / 59.0 ± 0.9 / 66.8 ± 1.2 / 53.8 ± 0.9**
Height (cm) / 159.8 ± 0.7 / 167.3 ± 0.7 / 154.8 ± 0.6**
BMI (kg·m-2) / 23.1 ± 0.3 / 23.9 ± 0.4 / 22.6 ± 0.4*
%BF / 30.3 ± 0.5 / 28.8 ± 0.7 / 31.2 ± 0.6**
FM (kg) / 18.0 ± 0.4 / 19.5 ± 0.7 / 17.1 ± 0.6**
FFM (kg) / 40.9 ± 0.6 / 47.4 ± 0.6 / 36.7 ± 0.4**
W (cm) / 78.0 ± 0.9 / 83.9 ± 1.0 / 74.1 ± 1.0**
H (cm) / 93.3 ± 0.5 / 94.6 ± 0.6 / 92.5 ± 0.8*
W/H ratio / 0.83 ± 0.01 / 0.89 ± 0.01 / 0.80 ± 0.01**
SBP (mmHg) / 116.1 ± 1.2 / 120.8 ± 2.1 / 112.9 ± 1.2**
DBP (mmHg) / 73.8 ± 0.8 / 77.1 ± 1.5 / 71.6 ± 0.9**
MAP (mmHg) / 87.9 ± 0.9 / 91.7 ± 1.6 / 85.4 ± 0.9**
HR (beats·min-1) / 76.1 ± 0.9 / 73.7 ± 1.3 / 77.7 ± 1.1*
Peak HR (beats·min-1) / 152.9 ± 1.3 / 149.2 ± 1.7 / 155.4 ± 1.8**
HRR (beats) / 30.3 ± 0.8 / 27.7 ± 1.1 / 32.1 ± 1.1**
VO2 peak (mL·kg-1·mim-1) / 24.4 ± 0.7 / 24.5 ± 1.1 / 24.3 ± 1.0
Estimated VO2 peak (mL·kg-1·mim-1) / 24.3 ± 0.4 / 24.5 ± 0.7 / 24.1 ± 0.6
Fasting glucose (mg·dL-1) / 78.1 ± 0.7 / 79.8 ± 1.1 / 76.7 ± 0.9*
TG (mg·dL-1) / 95.6 ± 3.2 / 118.6 ± 6.0 / 83.5 ± 3.6**
TC (mg·dL-1) / 196.7 ± 1.9 / 197.5 ± 3.3 / 194.5 ± 2.5
LDL-C (mg·dL-1) / 126.8 ± 1.7 / 123.0 ± 3.3 / 128.2 ± 2.0
HDL-C (mg·dL-1) / 50.6 ± 1.0 / 50.6 ± 2.1 / 49.4 ± 1.1
TG/HDL-C / 1.9 ± 0.1 / 2.5 ± 0.2 / 1.8 ± 0.1**
Values are mean ± SE; BM = Body Mass; BMI = Body Mass Index; %BF = Percentage of Body Fat; FM = Fat Mass; FFM = Fat Free Mass; W = Waist Circumference; H = Hip Circumference; W/H ratio = Waist to Hip Circumference Ratio; SBP = Systolic Blood Pressure; DBP = Diastolic Blood Pressure; MAP = Mean Arterial Pressure; HR = Heart Rate; HRR = Heart Rate Recovery; VO2 peak = Peak Oxygen Consumption; TG = Triglycerides; TC = Total Cholesterol; LDL-C = Low-Density Lipoprotein Cholesterol; HDL-C = High-Density Lipoprotein Cholesterol; *P<0.05, **P<0.01.
Table 2 describes the overall relationships between measured VO2 peak and the variables under study for all subjects and then individualized for men and women. The results showed significant relationships between VO2 peak and age (r = -0.24, P0.05), LDL-C (r = -0.37, P<0.01), HDL-C (r = 0.35, P<0.05), BMI (r = -0.25, P<0.01), %BF (r = -0.18, P<0.05), FM (r = -0.20, P<0.05), W (r = -0.24, P<0.01), H (r = -0.25, P<0.01), W/H ratio (r = -0.18, P<0.05), peak HR (r = 0.65, P<0.01), and HRR (r = 0.17, P<0.05) when all subjects were grouped. The high overall correlation between VO2 peak and the variables under study; LDL-C, HDL-C, and W were used to develop regression equations to estimate VO2 peak in the grouped subjects. The regression equation for all subjects resulted in a mean difference of -0.6 mL·kg-1·min-1, ranging from -1.6 to 0.4 mL·kg-1·mim-1 and the standard error of the calculated estimation was 5.4 mL·kg-1·min-1…
VO2 peak = 46.96 + (-0.14´LDL-C) + (0.24´HDL-C) + (-0.22´W); P0.0001
(Table 3).
In men, the results showed significant relationships between VO2 peak and HDL-C (r = 0.32, P<0.05), W (r = -0.14, P<0.05), and peak HR (r = 0.67, P<0.05) (Table 2). The overall correlation between VO2 peak and the variables under study; HDL-C and waist circumference were used to develop regression equations for estimated VO2 peak in the healthy sedentary men. The regression equation had an overall mean difference of -0.9 mL·kg-1·min-1, ranging from -2.2 to 0.5 mL·kg-1·min-1 and the standard error of the calculated estimate was ±4.4 mL·kg-1·min-1…
VO2 peak = 35.58 + (0.30´HDL-C) + (-0.32´W); P0.0001
(Table 3).
In the healthy sedentary women, the results showed significant relationships were obtained between VO2 peak and age (r = -0.30, P<0.01), TG (r = -0.31, P<0.01), LDL-C (r = -0.50, P<0.01), HDL-C (r = 0.24, P<0.05), BM (r = -0.31, P<0.01), BMI (r = -0.36, P<0.01), FM (r = -0.27, P<0.05), FFM (r = -0.30, P<0.01), W (r = -0.34, P<0.01), H (r = -0.26, P<0.05), W/H ratio (r = -0.32, P<0.05), and peak HR (r = 0.66, P<0.01) (Table 2). The high overall correlation between VO2 peak and the variables under study; LDL-C and HDL-C were used to develop regression equations for estimated peak VO2 peak in healthy sedentary women. The regression equation resulted in an overall mean difference of 0.3 mL·kg-1·min-1, ranging from -1.1 to 1.7 mL·kg-1·min-1 and the standard error of the estimate was ±5.8 mL·kg-1·min-1…
VO2 peak = 44.57 + (-0.28´LDL-C) + (0.326´HDL-C); P0.0001
(Table 3).
Table 2. Relationship Between VO2 peak and Cardiovascular Risk Factors in Subjects.
Total(N = 128) / Men
(N = 51) / Women
(N = 77)
Age (yr) / -0.24* / -0.07 / -0.30**
BM (kg) / -0.16 / -0.09 / -0.31**
Height (cm) / -0.25** / -0.12 / -0.36**
BMI (kg·m-2) / -0.18* / -0.08 / -0.22
%BF / -0.20* / -0.09 / -0.27*
FM (kg) / -0.10 / -0.06 / -0.30**
FFM (kg) / 0.24** / -0.14* / -0.34**
W (cm) / -0.25** / -0.20 / -0.26*
H (cm) / -0.18* / -0.07 / -0.32**
W/H ratio / -0.02 / -0.05 / -0.02
SBP (mmHg) / 0.65** / 0.67** / 0.66**
DBP (mmHg) / 0.17* / 0.15 / 0.22
MAP (mmHg) / 0.05 / -0.03 / 0.16
HR (beats·min-1) / 0.04 / -0.08 / 0.18
Peak HR (beats·min-1) / -0.05 / -0.04 / -0.10
HRR (beats) / -0.08 / -0.11 / -0.09
Fasting glucose (mg·dL-1) / -0.07 / -0.05 / -0.06
TG (mg·dL-1) / -0.16 / -0.09 / -0.31**
TC (mg·dL-1) / -0.37** / -0.10 / -0.50**
LDL-C (mg·dL-1) / 0.35** / 0.32* / 0.24*
HDL-C (mg·dL-1) / -0.24* / -0.07 / -0.30**
TG/HDL-C / -0.16 / -0.09 / -0.31**
Values are expressed as Spearman’s rho correlation coefficient (r). BM = Body Mass; BMI = Body Mass Index; %BF = Percentage of Body Fat; FM = Fat Mass; FFM = Fat Free Mass; W = Waist Circumference; H = Hip Circumference; W/H ratio = Waist to Hip Circumference Ratio; SBP = Systolic Blood Pressure; DBP = Diastolic Blood Pressure; MAP = Mean Arterial Pressure; HR = Heart Rate; HRR = Heart Rate Recovery; VO2 peak = Peak Oxygen Consumption; TG = Triglycerides; TC = Total Cholesterol; LDL-C = Low-Density Lipoprotein Cholesterol; HDL-C = High-Density Lipoprotein Cholesterol; *P<0.05, **P<0.01.