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Journal of the American College of Nutrition Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/uacn20
Physical activity and condition, dietary habits, and serum lipids in second-year medical students. a
a
a
a
D Troyer , I H Ullrich , R A Yeater & R Hopewell a
Department of Medicine, West Virginia University, Morgantown. Published online: 02 Sep 2013.
To cite this article: D Troyer, I H Ullrich, R A Yeater & R Hopewell (1990) Physical activity and condition, dietary habits, and serum lipids in second-year medical students., Journal of the American College of Nutrition, 9:4, 303-307, DOI: 10.1080/07315724.1990.10720384 To link to this article: http://dx.doi.org/10.1080/07315724.1990.10720384
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Physical Activity and Condition, Dietary Habits, and Serum Lipids in Second-Year Medical Students Devin Troyer, Irma H. Ullrich, Rachel A. Yeater, and Regina Hopewell Departments of Medicine and Sports and Exercise Studies, West Virginia University, Morgantown
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Key words: physical fitness, lipids, hypertension, medical students, preventive medicine Level of physical activity has been found to be an independent risk factor for coronary heart disease. Because lifestyle and dietary habits are frequently established by early adulthood, we examined the physical activity, physical fitness, body composition, plasma lipids, and diets of a group of second-year medical students. Medical students were studied because of the presumption that they were knowledgeable about exercise and appropriate diet and would have future influence on their patients. A questionnaire which assessed physical activity was returned by 69 (89%) of the 80 students. Over 50% reported no hard or very hard physical activity either during the week or on weekends. Three subjects were smokers. Body composition, cardiovascular fitness, and plasma lipids were assessed in 20 subjects selected at random from the 69. Five of the 15 men, but none of the five women, had greater-than-desirable body fat. Cardiovascular fitness was at least average compared to normal values, but three had hypertension at rest and 12 had hypertensive responses to exercise. Seven of the men had LDL cholesterol above 130 mg/dl and three had LDL:HDL ratios greater than 3. There was a positive correlation (r = 0.5, p = 0.02) between hard/very hard activity assessed by questionnaire and VO, mx and a negative correlation (r = 0.4, p = 0.05) between VO, mlx and percent fat. All 20 subjects reported above average to severe amounts of stress. Analysis of a 48-hr diet record of 22 students showed an average consumption of 47% carbohydrates, 17% protein, and 36% fat. The polyunsaturated/saturated ratio was 0.43. The average daily sodium intake was 2744 mg with a sodium/potassium ratio of 1.15. We conclude that many of these medical students are themselves at increased cardiovascular risk because of inactivity, hypertension, hyperlipidemia, and stress. Their personal lifestyles and lack of classroom instruction on the benefits of exercise make it unlikely that they will use exercise as a therapeutic modality for their patients.
INTRODUCTION West Virginia is primarily a rural state with a high incidence of both poverty and coronary artery disease [1]. In addition to hypertension, hyperlipidemia, and smoking, the level of physical activity [2-5], and there fore fitness, has been found to be an independent and strong risk factor for heart disease. Thus, a logical, inex pensive strategy for improving the cardiovascular status of West Virginians would be to emphasize lifestyle modifications such as increasing exercise and changing diet. Physicians may be important influences in the lives of their patients, both through the practice of medicine as well as serving as role models. Yet, they frequently are not involved in either recommending lifestyle changes for their patients [6] nor in adopting such changes in
their own lives. Physicians have no improvement over the cardiovascular mortality found in other similar socioeconomic groups [7], suggesting that they either have additional risk factors or they have not modified their lifestyles appropriately. Furthermore, they have a higher suicide rate than a similar managerial group, fur nishing further evidence of maladaptive behavior [7]. Because personal lifestyles and attitudes are frequent ly established by early adulthood, we evaluated the presence of certain cardiovascular risk factors among medical students. Although they represent a group whose common interest is health with a special interest in at taining knowledge of it and disease, the application of this knowledge to their own lives is not actively en couraged [8] and may even be discouraged by the large demands on their time. Further, the presence of hyper lipidemia, hypertension, inactivity, and stress among
Addressreprintrequests lo Irma Ullrich, M.D., Department of Medicine, WVU Medical Center, Morgantown, West Virginia 26505.
Journal of the American College of Nutrition, Vol. 9, No. 4, 303-307 (1990) © 1990 John Wiley & Sons, Inc.
CCC 0731-5724/90/040303-05$04.00
Physical Fitness, Lipids, Hypertension, Medical Students medical students may presage ischemie heart disease as these students age. We felt that their own habits might also influence their future practice of medicine.
Downloaded by [ECU Libraries] at 17:53 21 April 2015
METHODS The second-year class of medical students at West Virginia University in Morgantown in 1986 consisted of 80 students (59 men and 21 women), all of whom were West Virginia residents. Sixty-nine students (50 men and 19 women) volunteered to complete a questionnaire on physical activity. The instrument used was a modified form of a 7-day recall questionnaire developed by Sallis et al [9] and asked students to recall the amount of time spent sleeping and in various levels of physical activity over the preceding week. Examples of moderate, hard, and very hard activities were given. Moderate activity included activities such as sweeping, mowing the lawn, walking, golfing, or calisthenic exercises. Examples of hard activity were scrubbing floors, dancing, or halfcourt basketball; very hard activity illustrations were running, playing racquetball, or tennis singles. The ques tionnaire also asked whether the recent activity level was representative of the preceding 3-6 months. Demographic information, as well as a brief medical and family history of coronary risk factors, were also ob tained. To assess the validity of the questionnaire to predict aerobic fitness, 20 subjects were randomly selected from the 69 who completed the questionnaire and were offered the opportunity to have their cardiovas cular fitness assessed by laboratory methods. Since physical fitness has been shown to affect lipid values, serum lipids were also evaluated. Physical fitness was assessed by measuring maximal oxygen consumption (V0 2max ); this was measured using a modified Balke treadmill protocol [10], which required the subject to walk at a constant speed (about 3 mph) on a motordriven treadmill. The treadmill elevation was increased 2% at the end of the first minute and 1 % each minute thereafter until the subject became too tired to continue. Expired air samples were obtained during the final minute of exercise to determine oxygen consumption. Heart rate and blood pressure were monitored throughout the test and during recovery. Body composi tion was determined by hydrostatic weighing [11]. Serum lipids were determined from a venous blood sample which was obtained following a 12-hr fast. Triglycérides [12] and total cholesterol [13] were measured enzymatically; HDL cholesterol was measured in the same manner in the supernatant of a phosphotungstate-magnesium chloride precipitate. Interassay variation was 8%, intraassay variation was 3%. LDL
304
cholesterol was calculated by subtracting the sum of HDL cholesterol and one-fifth of the triglycéride value from total cholesterol after the method of Friedewald [14]. All class members (80) were requested to complete a 48-hr diet record by recording all foods eaten on 2 con secutive typical weekdays. Twenty-two persons (20 men, two women) submitted this information. The diet records were analyzed using the Nutritionist II program (com mercially available; uses USDA Home/Garden Bulletin No. 7, and USDA Series 108-1,108-12 as database) by N2 Computing (Silverton, OR). The study was approved by the Human Subjects Committee of West Virginia University. Informed consent was obtained from each subject. Data were analyzed using Pearson product mo ment correlations and independent t tests.
RESULTS Results from the activity questionnaire are shown in Table 1. Moderate activities were most frequent, with 51% of students participating 30 minutes during the week but only 10% had 90 minutes or more. During the week, 65% of students reported no hard activity and 51% performed no very hard activity. Weekend ratings showed that 57% still had no hard ac tivity and 75% performed no very hard activities. Thus, over 50% of students reported zero hours per week of hard or very hard activities. Overall, the average time spent per week in moderate activities was 41 minutes, hard activities 13 minutes, and very hard activities 11 minutes. Questionnaire data from the 20 students (16 men, four women) selected for testing were not different from the larger group of 69 by independent t test; the group, therefore, was felt to be a representative sample. All of the 20 reported the amount of stress they felt as medical students to be above average or severe on a scale of little, average, above average, or severe. Nineteen of the 20 subjects reached their predicted maximal heart rate during testing (220 - age). Maximum oxygen consumption (V02max) showed a range of 32-60 and a mean of 47 ± 2 (mean ± SEM) ml/kg/min in the men and 38 ± 3 in the women. These values were com pared with age- and sex-matched norms, and all were shown to fall within the range of average or better. Blood pressure monitoring done in conjunction with treadmill testing demonstrated three subjects (15%) to have high resting pressures (diastolic > 90 and/or systolic > 140 mm Hg). Twelve subjects (60%) had abnormal blood pressure responses to exercise, defined as an increase in diastolic pressure above 90 mm Hg.
VOL. 9, NO. 4
Physical Fitness, Lipids, Hypertension, Medical Students Table 1. Time Spent in Various Levels of Physical Activity Hours
Moderate activity weekends weekdays
Hard activity weekends weekdays
0
17a
23
65
Vi 1
51 20 5 5
25 29 3
26 7
\Vt 2 2V4 3
4 1
3V4 4+
3 4
1
57 23 12
Very hard activity weekdays weekends 51 41
75 16
7
6 1
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"Percentage of 60 subjects.
Body fat among the five women ranged from 19 to 25%, with a mean of 23 ± 1.4% (SEM). The men had a range of 4-24% and a mean of 13%. Desirable composi tion for young people is body fat 25% or less for women and less than 15% for men [15]. Five of the men were overweight using this criterion. Total serum cholesterol was 207 ± 12 mg/dl (mean + SEM) in the men and 177 ± 9 in the women. Triglycérides were 112 ± 18 and 71 ± 11 mg/dl in the men and women, respectively. HDL cholesterol levels were 61 ± 5 in the men and 84+17 mg/dl in the women. Calculated LDL cholesterol was 124 ± 13 and 78 ± 14 mg/dl in the men and women, respectively. These values were compared to age- and sex-matched norms taken from Lipid Research Clinics population studies in the United States and Canada [16]. Total cholesterol was greater than the 50th percentile in 85% of the subjects, and 40% of the subjects had a total cholesterol greater than the 90th percentile. Triglycérides and LDL cholesterol were found to be greater than the 90th per centile in 15 and 30% of the subjects, respectively. HDL cholesterol, a protective lipid, was found to be greater than the 90th percentile in 60% of the subjects. Three subjects (15%) had LDL:HDL ratios greater than 3.0. A positive correlation was found between reported hard/very hard activity and V0 2max (r = 0.5, p = 0.02). There was a significant negative correlation between percent fat and V0 2max (r = 0.4, p = 0.05). Finally, there was a suggestive positive correlation between V0 2max and HDL cholesterol (p = 0.08). Dietary records for two women and 20 men showed an average caloric intake of 1949 kcal/day with 47% derived from carbohydrate, 17% from protein, 36% from
fat, and 1% from alcohol. Only nine of the 22 subjects consumed 50% or more of their calories as carbohydrate. Crude fiber consumption was 6 g/day. Thirty-five per cent of fat was saturated and 15% polyunsaturated, with poly unsaturated: saturated ratio of 0.45. Monounsaturated fat accounted for 30% of the total fat intake. Average daily cholesterol intake was 251 mg, but the range was 31-835 mg; only 4 of 44 days analyzed had over 500 mg of cholesterol but 12 days were above 300 mg. Vitamin A, vitamin C, thiamine, riboflavin, niacin, and calcium were above 75% of the recommended dietary allowance (RDA) [17]. The average daily intake of sodium and potassium was 2744 and 2376 mg, respec tively. Iron intake by women was 68% of the RDA (12 mg/day).
DISCUSSION This study has demonstrated that medical students, presumably a group interested and knowledgeable about cardiovascular risk factors and disease, have done little to improve their own risk profiles. Greater than 50% of those surveyed reported doing no hard or very hard ac tivity during the week or on weekends. Sixty percent (12 out of 20) had resting hypertension and/or hypertensive responses to exercise. In an epidemiologie study, Blair et al [18] demonstrated that people with low levels of physical activity had a relative risk of 1.5 for developing hypertension when compared to highly fit people. In ad dition to the relative inactivity in the majority of the students, the fact that all 20 subjects reported above average to severe amounts of stress in their lives may
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Physical Fitness, Lipids, Hypertension, Medical Students also play a role in the initiation of hypertension. A diet which contains increased amounts of potassium relative to sodium has been postulated to be protective against hypertension [19]; our subjects had a ratio of sodium to potassium of 1:1.15. Thus, the etiology of their hyperten sion is likely multifactorial. Earlier studies have shown a positive correlation be tween the 7-day physical activity recall questionnaire and actual physical activity levels. Our study did not measure actual physical activity, but chose to measure physical condition by means of V0 2max assessment. Analysis showed a positive significant correlation be tween reported hard/very hard activity and V0 2max , in dicating that the questionnaire was valid in predicting aerobic fitness if this category of activity (hard/very hard) was considered. Interestingly, when comparing total reported physical activity and V0 2 „ ^ , the correla tion was not significant. This is best explained by the fact that activities included under "moderate" activities most likely would not increase heart rate significantly for prolonged periods (> 20 min) and, therefore, would not be expected to increase aerobic capacity. The posi tive correlation between V0 2max and hard/very hard physical activity assessed by questionnaire may be use ful to estimate physical condition when laboratory methods are unavailable. One might also keep in mind that, although the V0 2 „^ results fall in the average-or-better range groups, these norms are based on age- and sex-matched Ameri cans and, therefore, represent the physical condition of the general population in this country and not necessarily that of other countries nor an ideal. The elevated LDL:HDL ratios in some subjects may reflect contributions of a high-fat diet and lack of exer cise. Analysis of the diets suggest that these medical students ate a diet somewhat higher in carbohydrate (47%) than the usual Western diet [20] (43% car bohydrate, 40% fat, 17% protein, 12 g fiber, and 400 mg cholesterol), but over 50% failed to achieve the 50% carbohydrate level recommended in the Prudent diet [21]. However, 73% had less than 300 mg daily intake of cholesterol. Twenty-five percent of the 20 subjects had more than desirable body fat, indicating an imbalance between energy intake and expenditure. The results of this study cannot predict changes in diet or activity which may occur in the future. Secondyear medical students have not completed their training, so that their level of knowledge and its application might be expected to increase. Alternatively, the converse may also be true, that, like nutrition [22], interest in exercise and other forms of prevention of heart disease may decline with increased level of training.
306
At the time they were studied, many of these medical students were inactive, did not eat a prudent diet, had hypertension and abnormal lipids, and were overweight and stressed. The implications are that these students personally have many risk factors for developing coronary artery disease, and, if they continue unhealthy habits, this will make them more likely to have future heart disease. The absence of appropriate personal life styles makes it improbable that they will suggest such health strategies for their patients. Lifestyle changes would appear to be of special importance in areas like West Virginia, with limited economic resources in which ischemie coronary disease is a major cause of morbidity and mortality. Medical students, as well as practicing physicians, may need special, personal attention to allow them and their patients to realize the potential benefits of increased exercise and dietary modification.
REFERENCES 1. Health Statistics Center, Department of Health: "Vital Statistics, State of West Virginia." Charleston: Department of Health, Health Statistics Center, 1986. 2. Leon AS, Connett J, Jacobs DR, Rauramaa R: Leisure time physical activity levels and risk of coronary heart disease and death. The multiple risk factor intervention trial. JAMA 258:2388-2395, 1987. 3. Salonen JT, Slater JS, Tuomilehto, Rauramaa R: Leisure time and occupational physical activity:riskof death from ischemie heart disease. Am J Epidemiol 127:87-94, 1988. 4. Slattery ML, Jacobs DR Jr: Physical fitness and cardiovas cular disease mortality. The US railroad study. Am J Epidemiol 127:571-580, 1988. 5. Paffenbarger RS Jr, Wing AL, Hyde RT: Physical activity as an index of heart attack risk in college alumni. Am J Epidemiol 108:161-175, 1978. 6. Wechsler H, Levine S, Idelson RK, Rohman M, Taylor JO: The physician's role in health promotion — a survey of primary care practitioners. N Engl J Med 308:97-100, 1983. 7. Rimpela AH, Nurminen MM, Pulkkinen PO, Rimpela MK, Valkonen T: Mortality of doctors: do doctors benefit from their medical knowledge? Lancet 1:84-86, 1987. 8. Levy BS, Goldberg R, Rippe J, Love D: A regular physi cal exercise program for medical students: learning about prevention through participation. J Med Educ 59:596-598, 1984. 9. Sallis JF, Haskell WL, Wood PD, et al: Physical activity assessment methodology in the Five City Project. Am J Epidemiol 121:91-106, 1985. 10. Balke B, Ware R: An experimental study of physical fit ness of Air Force personnel. US Armed Forces Med J 10:675, 1959.
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Physical Fitness, Lipids, Hypertension, Medical Students 11. Warner JG Jr, Yeater R, Sherwood L, Weber K: A hydro static weighing method using total lung capacity and a small tank. Br J Sports Med 20:17-21,1986. 12. Bucolo G, David H: Quantitative determination of serum triglycérides by the use of enzymes. Clin Chem 19:476482, 1973. 13. Allain CC, Poon YS, Chan CSG, et al: Enzymatic deter mination of total serum cholesterol. Clin Chem 20:470475, 1974. 14. Friedewald WT, Levy RI, Frederickson DS: Estimation of the concentration of low-density-lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 18:499-502, 1972. 15. McArdle WD, Katch FI, Katch VL (eds): Body composi tion assessment. In: "Exercise Physiology." Philadelphia: Lea & Febiger, pp 483-512, 1986. 16. Schaefer EJ, Levy RI: Pathogenesis and management of lipoprotein disorders. N Engl J Med 312:1300-1310, 1985. 17. National Research Council: "Recommended Dietary Al lowances." Washington, DC: US Government Printing Of fice, 1980.
18. Blair S, Goodyear N, Gibbons L, Cooper K: Physical fit ness and incidence of hypertension in healthy normotensive men and women. JAMA 252: 487-490,1984. 19. Langford HG: Dietary potassium and hypertension: epidemiologie data. Ann Intern Med 98:770-772, 1983. 20. Abraham S, Carroll MD: Fats, cholesterol and sodium in take in the diet of persons 1-74 years. United States Vital and Health Statistics Advance Data, Series No 54, 1981. 21. Scott LW, Foreyt JP, Gotto AM: Variations on the prudent diet. In Feldman EB (ed): "Nutrition and Heart Disease." New York-Edinburgh-London-Melbourne: Churchill Livingstone, pp 183-202, 1983. 22. Morgan SL, Weinsier RL, Boker JR, Brooks CM, Feldman EB, Read MS: A comparison of nutrition knowledge of freshmen and senior medical students: a collaborative study of southeastern medical schools. J Am Coll Nutr 7:193-197, 1988.
Received March 1989 ; revision accepted December 1989.
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Journal of the American College of Nutrition Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/uacn20
Physical activity and condition, dietary habits, and serum lipids in second-year medical students. a
a
a
a
D Troyer , I H Ullrich , R A Yeater & R Hopewell a
Department of Medicine, West Virginia University, Morgantown. Published online: 02 Sep 2013.
To cite this article: D Troyer, I H Ullrich, R A Yeater & R Hopewell (1990) Physical activity and condition, dietary habits, and serum lipids in second-year medical students., Journal of the American College of Nutrition, 9:4, 303-307, DOI: 10.1080/07315724.1990.10720384 To link to this article: http://dx.doi.org/10.1080/07315724.1990.10720384
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
Physical Activity and Condition, Dietary Habits, and Serum Lipids in Second-Year Medical Students Devin Troyer, Irma H. Ullrich, Rachel A. Yeater, and Regina Hopewell Departments of Medicine and Sports and Exercise Studies, West Virginia University, Morgantown
Downloaded by [ECU Libraries] at 17:53 21 April 2015
Key words: physical fitness, lipids, hypertension, medical students, preventive medicine Level of physical activity has been found to be an independent risk factor for coronary heart disease. Because lifestyle and dietary habits are frequently established by early adulthood, we examined the physical activity, physical fitness, body composition, plasma lipids, and diets of a group of second-year medical students. Medical students were studied because of the presumption that they were knowledgeable about exercise and appropriate diet and would have future influence on their patients. A questionnaire which assessed physical activity was returned by 69 (89%) of the 80 students. Over 50% reported no hard or very hard physical activity either during the week or on weekends. Three subjects were smokers. Body composition, cardiovascular fitness, and plasma lipids were assessed in 20 subjects selected at random from the 69. Five of the 15 men, but none of the five women, had greater-than-desirable body fat. Cardiovascular fitness was at least average compared to normal values, but three had hypertension at rest and 12 had hypertensive responses to exercise. Seven of the men had LDL cholesterol above 130 mg/dl and three had LDL:HDL ratios greater than 3. There was a positive correlation (r = 0.5, p = 0.02) between hard/very hard activity assessed by questionnaire and VO, mx and a negative correlation (r = 0.4, p = 0.05) between VO, mlx and percent fat. All 20 subjects reported above average to severe amounts of stress. Analysis of a 48-hr diet record of 22 students showed an average consumption of 47% carbohydrates, 17% protein, and 36% fat. The polyunsaturated/saturated ratio was 0.43. The average daily sodium intake was 2744 mg with a sodium/potassium ratio of 1.15. We conclude that many of these medical students are themselves at increased cardiovascular risk because of inactivity, hypertension, hyperlipidemia, and stress. Their personal lifestyles and lack of classroom instruction on the benefits of exercise make it unlikely that they will use exercise as a therapeutic modality for their patients.
INTRODUCTION West Virginia is primarily a rural state with a high incidence of both poverty and coronary artery disease [1]. In addition to hypertension, hyperlipidemia, and smoking, the level of physical activity [2-5], and there fore fitness, has been found to be an independent and strong risk factor for heart disease. Thus, a logical, inex pensive strategy for improving the cardiovascular status of West Virginians would be to emphasize lifestyle modifications such as increasing exercise and changing diet. Physicians may be important influences in the lives of their patients, both through the practice of medicine as well as serving as role models. Yet, they frequently are not involved in either recommending lifestyle changes for their patients [6] nor in adopting such changes in
their own lives. Physicians have no improvement over the cardiovascular mortality found in other similar socioeconomic groups [7], suggesting that they either have additional risk factors or they have not modified their lifestyles appropriately. Furthermore, they have a higher suicide rate than a similar managerial group, fur nishing further evidence of maladaptive behavior [7]. Because personal lifestyles and attitudes are frequent ly established by early adulthood, we evaluated the presence of certain cardiovascular risk factors among medical students. Although they represent a group whose common interest is health with a special interest in at taining knowledge of it and disease, the application of this knowledge to their own lives is not actively en couraged [8] and may even be discouraged by the large demands on their time. Further, the presence of hyper lipidemia, hypertension, inactivity, and stress among
Addressreprintrequests lo Irma Ullrich, M.D., Department of Medicine, WVU Medical Center, Morgantown, West Virginia 26505.
Journal of the American College of Nutrition, Vol. 9, No. 4, 303-307 (1990) © 1990 John Wiley & Sons, Inc.
CCC 0731-5724/90/040303-05$04.00
Physical Fitness, Lipids, Hypertension, Medical Students medical students may presage ischemie heart disease as these students age. We felt that their own habits might also influence their future practice of medicine.
Downloaded by [ECU Libraries] at 17:53 21 April 2015
METHODS The second-year class of medical students at West Virginia University in Morgantown in 1986 consisted of 80 students (59 men and 21 women), all of whom were West Virginia residents. Sixty-nine students (50 men and 19 women) volunteered to complete a questionnaire on physical activity. The instrument used was a modified form of a 7-day recall questionnaire developed by Sallis et al [9] and asked students to recall the amount of time spent sleeping and in various levels of physical activity over the preceding week. Examples of moderate, hard, and very hard activities were given. Moderate activity included activities such as sweeping, mowing the lawn, walking, golfing, or calisthenic exercises. Examples of hard activity were scrubbing floors, dancing, or halfcourt basketball; very hard activity illustrations were running, playing racquetball, or tennis singles. The ques tionnaire also asked whether the recent activity level was representative of the preceding 3-6 months. Demographic information, as well as a brief medical and family history of coronary risk factors, were also ob tained. To assess the validity of the questionnaire to predict aerobic fitness, 20 subjects were randomly selected from the 69 who completed the questionnaire and were offered the opportunity to have their cardiovas cular fitness assessed by laboratory methods. Since physical fitness has been shown to affect lipid values, serum lipids were also evaluated. Physical fitness was assessed by measuring maximal oxygen consumption (V0 2max ); this was measured using a modified Balke treadmill protocol [10], which required the subject to walk at a constant speed (about 3 mph) on a motordriven treadmill. The treadmill elevation was increased 2% at the end of the first minute and 1 % each minute thereafter until the subject became too tired to continue. Expired air samples were obtained during the final minute of exercise to determine oxygen consumption. Heart rate and blood pressure were monitored throughout the test and during recovery. Body composi tion was determined by hydrostatic weighing [11]. Serum lipids were determined from a venous blood sample which was obtained following a 12-hr fast. Triglycérides [12] and total cholesterol [13] were measured enzymatically; HDL cholesterol was measured in the same manner in the supernatant of a phosphotungstate-magnesium chloride precipitate. Interassay variation was 8%, intraassay variation was 3%. LDL
304
cholesterol was calculated by subtracting the sum of HDL cholesterol and one-fifth of the triglycéride value from total cholesterol after the method of Friedewald [14]. All class members (80) were requested to complete a 48-hr diet record by recording all foods eaten on 2 con secutive typical weekdays. Twenty-two persons (20 men, two women) submitted this information. The diet records were analyzed using the Nutritionist II program (com mercially available; uses USDA Home/Garden Bulletin No. 7, and USDA Series 108-1,108-12 as database) by N2 Computing (Silverton, OR). The study was approved by the Human Subjects Committee of West Virginia University. Informed consent was obtained from each subject. Data were analyzed using Pearson product mo ment correlations and independent t tests.
RESULTS Results from the activity questionnaire are shown in Table 1. Moderate activities were most frequent, with 51% of students participating 30 minutes during the week but only 10% had 90 minutes or more. During the week, 65% of students reported no hard activity and 51% performed no very hard activity. Weekend ratings showed that 57% still had no hard ac tivity and 75% performed no very hard activities. Thus, over 50% of students reported zero hours per week of hard or very hard activities. Overall, the average time spent per week in moderate activities was 41 minutes, hard activities 13 minutes, and very hard activities 11 minutes. Questionnaire data from the 20 students (16 men, four women) selected for testing were not different from the larger group of 69 by independent t test; the group, therefore, was felt to be a representative sample. All of the 20 reported the amount of stress they felt as medical students to be above average or severe on a scale of little, average, above average, or severe. Nineteen of the 20 subjects reached their predicted maximal heart rate during testing (220 - age). Maximum oxygen consumption (V02max) showed a range of 32-60 and a mean of 47 ± 2 (mean ± SEM) ml/kg/min in the men and 38 ± 3 in the women. These values were com pared with age- and sex-matched norms, and all were shown to fall within the range of average or better. Blood pressure monitoring done in conjunction with treadmill testing demonstrated three subjects (15%) to have high resting pressures (diastolic > 90 and/or systolic > 140 mm Hg). Twelve subjects (60%) had abnormal blood pressure responses to exercise, defined as an increase in diastolic pressure above 90 mm Hg.
VOL. 9, NO. 4
Physical Fitness, Lipids, Hypertension, Medical Students Table 1. Time Spent in Various Levels of Physical Activity Hours
Moderate activity weekends weekdays
Hard activity weekends weekdays
0
17a
23
65
Vi 1
51 20 5 5
25 29 3
26 7
\Vt 2 2V4 3
4 1
3V4 4+
3 4
1
57 23 12
Very hard activity weekdays weekends 51 41
75 16
7
6 1
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"Percentage of 60 subjects.
Body fat among the five women ranged from 19 to 25%, with a mean of 23 ± 1.4% (SEM). The men had a range of 4-24% and a mean of 13%. Desirable composi tion for young people is body fat 25% or less for women and less than 15% for men [15]. Five of the men were overweight using this criterion. Total serum cholesterol was 207 ± 12 mg/dl (mean + SEM) in the men and 177 ± 9 in the women. Triglycérides were 112 ± 18 and 71 ± 11 mg/dl in the men and women, respectively. HDL cholesterol levels were 61 ± 5 in the men and 84+17 mg/dl in the women. Calculated LDL cholesterol was 124 ± 13 and 78 ± 14 mg/dl in the men and women, respectively. These values were compared to age- and sex-matched norms taken from Lipid Research Clinics population studies in the United States and Canada [16]. Total cholesterol was greater than the 50th percentile in 85% of the subjects, and 40% of the subjects had a total cholesterol greater than the 90th percentile. Triglycérides and LDL cholesterol were found to be greater than the 90th per centile in 15 and 30% of the subjects, respectively. HDL cholesterol, a protective lipid, was found to be greater than the 90th percentile in 60% of the subjects. Three subjects (15%) had LDL:HDL ratios greater than 3.0. A positive correlation was found between reported hard/very hard activity and V0 2max (r = 0.5, p = 0.02). There was a significant negative correlation between percent fat and V0 2max (r = 0.4, p = 0.05). Finally, there was a suggestive positive correlation between V0 2max and HDL cholesterol (p = 0.08). Dietary records for two women and 20 men showed an average caloric intake of 1949 kcal/day with 47% derived from carbohydrate, 17% from protein, 36% from
fat, and 1% from alcohol. Only nine of the 22 subjects consumed 50% or more of their calories as carbohydrate. Crude fiber consumption was 6 g/day. Thirty-five per cent of fat was saturated and 15% polyunsaturated, with poly unsaturated: saturated ratio of 0.45. Monounsaturated fat accounted for 30% of the total fat intake. Average daily cholesterol intake was 251 mg, but the range was 31-835 mg; only 4 of 44 days analyzed had over 500 mg of cholesterol but 12 days were above 300 mg. Vitamin A, vitamin C, thiamine, riboflavin, niacin, and calcium were above 75% of the recommended dietary allowance (RDA) [17]. The average daily intake of sodium and potassium was 2744 and 2376 mg, respec tively. Iron intake by women was 68% of the RDA (12 mg/day).
DISCUSSION This study has demonstrated that medical students, presumably a group interested and knowledgeable about cardiovascular risk factors and disease, have done little to improve their own risk profiles. Greater than 50% of those surveyed reported doing no hard or very hard ac tivity during the week or on weekends. Sixty percent (12 out of 20) had resting hypertension and/or hypertensive responses to exercise. In an epidemiologie study, Blair et al [18] demonstrated that people with low levels of physical activity had a relative risk of 1.5 for developing hypertension when compared to highly fit people. In ad dition to the relative inactivity in the majority of the students, the fact that all 20 subjects reported above average to severe amounts of stress in their lives may
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Physical Fitness, Lipids, Hypertension, Medical Students also play a role in the initiation of hypertension. A diet which contains increased amounts of potassium relative to sodium has been postulated to be protective against hypertension [19]; our subjects had a ratio of sodium to potassium of 1:1.15. Thus, the etiology of their hyperten sion is likely multifactorial. Earlier studies have shown a positive correlation be tween the 7-day physical activity recall questionnaire and actual physical activity levels. Our study did not measure actual physical activity, but chose to measure physical condition by means of V0 2max assessment. Analysis showed a positive significant correlation be tween reported hard/very hard activity and V0 2max , in dicating that the questionnaire was valid in predicting aerobic fitness if this category of activity (hard/very hard) was considered. Interestingly, when comparing total reported physical activity and V0 2 „ ^ , the correla tion was not significant. This is best explained by the fact that activities included under "moderate" activities most likely would not increase heart rate significantly for prolonged periods (> 20 min) and, therefore, would not be expected to increase aerobic capacity. The posi tive correlation between V0 2max and hard/very hard physical activity assessed by questionnaire may be use ful to estimate physical condition when laboratory methods are unavailable. One might also keep in mind that, although the V0 2 „^ results fall in the average-or-better range groups, these norms are based on age- and sex-matched Ameri cans and, therefore, represent the physical condition of the general population in this country and not necessarily that of other countries nor an ideal. The elevated LDL:HDL ratios in some subjects may reflect contributions of a high-fat diet and lack of exer cise. Analysis of the diets suggest that these medical students ate a diet somewhat higher in carbohydrate (47%) than the usual Western diet [20] (43% car bohydrate, 40% fat, 17% protein, 12 g fiber, and 400 mg cholesterol), but over 50% failed to achieve the 50% carbohydrate level recommended in the Prudent diet [21]. However, 73% had less than 300 mg daily intake of cholesterol. Twenty-five percent of the 20 subjects had more than desirable body fat, indicating an imbalance between energy intake and expenditure. The results of this study cannot predict changes in diet or activity which may occur in the future. Secondyear medical students have not completed their training, so that their level of knowledge and its application might be expected to increase. Alternatively, the converse may also be true, that, like nutrition [22], interest in exercise and other forms of prevention of heart disease may decline with increased level of training.
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At the time they were studied, many of these medical students were inactive, did not eat a prudent diet, had hypertension and abnormal lipids, and were overweight and stressed. The implications are that these students personally have many risk factors for developing coronary artery disease, and, if they continue unhealthy habits, this will make them more likely to have future heart disease. The absence of appropriate personal life styles makes it improbable that they will suggest such health strategies for their patients. Lifestyle changes would appear to be of special importance in areas like West Virginia, with limited economic resources in which ischemie coronary disease is a major cause of morbidity and mortality. Medical students, as well as practicing physicians, may need special, personal attention to allow them and their patients to realize the potential benefits of increased exercise and dietary modification.
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Physical Fitness, Lipids, Hypertension, Medical Students 11. Warner JG Jr, Yeater R, Sherwood L, Weber K: A hydro static weighing method using total lung capacity and a small tank. Br J Sports Med 20:17-21,1986. 12. Bucolo G, David H: Quantitative determination of serum triglycérides by the use of enzymes. Clin Chem 19:476482, 1973. 13. Allain CC, Poon YS, Chan CSG, et al: Enzymatic deter mination of total serum cholesterol. Clin Chem 20:470475, 1974. 14. Friedewald WT, Levy RI, Frederickson DS: Estimation of the concentration of low-density-lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 18:499-502, 1972. 15. McArdle WD, Katch FI, Katch VL (eds): Body composi tion assessment. In: "Exercise Physiology." Philadelphia: Lea & Febiger, pp 483-512, 1986. 16. Schaefer EJ, Levy RI: Pathogenesis and management of lipoprotein disorders. N Engl J Med 312:1300-1310, 1985. 17. National Research Council: "Recommended Dietary Al lowances." Washington, DC: US Government Printing Of fice, 1980.
18. Blair S, Goodyear N, Gibbons L, Cooper K: Physical fit ness and incidence of hypertension in healthy normotensive men and women. JAMA 252: 487-490,1984. 19. Langford HG: Dietary potassium and hypertension: epidemiologie data. Ann Intern Med 98:770-772, 1983. 20. Abraham S, Carroll MD: Fats, cholesterol and sodium in take in the diet of persons 1-74 years. United States Vital and Health Statistics Advance Data, Series No 54, 1981. 21. Scott LW, Foreyt JP, Gotto AM: Variations on the prudent diet. In Feldman EB (ed): "Nutrition and Heart Disease." New York-Edinburgh-London-Melbourne: Churchill Livingstone, pp 183-202, 1983. 22. Morgan SL, Weinsier RL, Boker JR, Brooks CM, Feldman EB, Read MS: A comparison of nutrition knowledge of freshmen and senior medical students: a collaborative study of southeastern medical schools. J Am Coll Nutr 7:193-197, 1988.
Received March 1989 ; revision accepted December 1989.
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