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VIETNAM MILITARY MEDICAL UNIVERSITYNGUYEN THI HIEN STUDY ON SOME CARDIOVASCULAR AND NERVOUS INDICATORS OF THAI BINH MEDICAL STUDENTS IN CONTROL AND EXAMINATION CONDITION Speciality: Phy

VIETNAM MILITARY MEDICAL UNIVERSITY

NGUYEN THI HIEN

STUDY ON SOME CARDIOVASCULAR

AND NERVOUS INDICATORS OF THAI BINH

MEDICAL STUDENTS IN CONTROL AND EXAMINATION CONDITION

Speciality: Physiology Code: 62 72 01 07

DOCTOR OF PHILOSOPHY DISSERTATION

HAnOi - 2013 THE PROJECT COMPLETED

In VIETNAM MILITARY MEDICAL UNIVERSITY

Assoc Prof PhD Tran Dang Dong Assoc Prof PhD Vuong Thi Hoa

Assoc Prof PhD Nguyen Trong Hung

The doctoral dissertation has been defended at the C ouncil Assessment of the dissertation at Vietnam Military Medical University

at 8.30 am - April 9th 2013.

THE DISSERTATION AVAILABLE AT:

- National Library of Vietnam

- Library – Vietnam Military Medical University

- Library – Thai Binh Medical University

Students are high quality workforce for the society in the future, they are

“life-sustaining element” in every country Health care for students is theimportant task not only for the school but also for the society This era, the era

of integration with the global boom of science and technology, along withenvironmental pollution, internal factors in the human body also become stressagents (stressors) Stress affects all social classes, including students There aremany factors causing neuropsychological stress for students during the time atthe university, especially for medical students Apart from the commonstressors of all students (living conditions, educational conditions…), medicalstudents have to spend the longest time at the university with very large amount

of theoretical and practical knowledge and many exams, therefore, they areunder high-pressure that cause many psychological functional strain In theworld, many studies showed that stressors can alter the function of the immunesystem, nervous system as well as cardiovascular and endocrine system inhuman

Stress is a reality of life, hence we need to understand the responses tostresses of the human body in every stressful status In doing this, we have toquantify stress levels by using objective measuring indicators In Vietnam, therehave been some studies on occupational stress of the scientists at the NationalInstitute of Labor Protection, National Institute of Occupational andEnvironmental Health and some universities However, very few studies havebeen conducted on the responses of the endocrine, cardiovascular andneurological systems of the individual to stress, including studies on students.From these reasons, we carried out the study "Study on some cardiovascular and nervous indicators of Thai Binh medical students in control and examination condition" with the following objectives:

1 Measuring some cardiovascular and neuropsychological indicators

of Thai Binh medical students before examination (control condition).

2 Evaluating some cardiovascular and neuropsychological and

endocrine indicators of Thai Binh medical students after intellectual activities (examination condition).

NEW SCIENTIFIC CONTRIBUTIONS OF THE DISSERTATION

- Providing data of some cardiovascular and neuropsychological indicators

of 600 male and female medical students from first year to fifth year incontrol condition

- Detecting changes of cardiovascular, neurological and endocrine functionafter intellectual activities (after examination) of medical students Afterthe exam, participants had cardiovascular strain indicator increased, ECGchanged, cortisol level as well as catecholamine level elevated

- The results of the dissertation contributes to the development of somebiological indicators and provides scientific evidences to propose solution

to lessen stress, improve health and intellectual property of students

THE STRUCTURE OF THE DESSERTATION

This desstertation consists of 152 pages: Introduction: 2 pages, Background: 41pages, Methods: 20 pages, Results: 46 pages, Disscusion : 40 pages, Conclusion:

2 pages, Proposal: 01 page, 60 tables, 25 figures and 139 references

CHAPTER 1 BACKGROUND 1.1 Cardiovascular indicators

1.1.1 Heart rate and blood pressure

Heart rate and arterial blood pressure are the simplest indicators to evaluatethe operational capacity of the human body These indicators are easy tomeasure, can be long-term or repeated measure The variations of them areeasily recognizable because when the labor intensity or the emotional levelincreased, those indicators rose follow Stressful work causes increased heartrate, increased blood pressure by stimulating the adrenal sympathetic nervoussystem Research of Droogleever on Dutch PhD students found that althoughblood pressure did not change significantly during the examination, but thedensity of peripheral Benzodiazepine receptor, allopregnanolon and cortisollevel of these students increased significantly Research of Makarenco onstudents during the stress test showed a decrease in the influence ofparasympathetic nerve on heart rate and metabolic stimulation but found anincrease of activity of the sympathetic nerve

In Vietnam, some authors have initially used the method that assesscardiovascular functions using heart rate and blood pressure in the job

with high neuropsychological stress such as work of pilots, soldiers, police,medical personnel, the commanders of the ship, the operators of automatedmachineries, the airport coordinators.

1.1.2 Mathematical statistical indicator of heart rate

In recent years, a number of authors have used the mathematical statisticalindicators of heart rate (MSIHR) of Baevski to evaluate cardiac function.Baevski is the first author who launched the principle of the index of 100consecutive RR intervals including: RR interval average (X), heart rate average(HRA), standard deviation, variation coefficient, mode (Mo), amplitude ofmode and variation interval of RR max and RR min (DX) Stress index iscalculated from above indicator (Stress index = AMo/2.DX.Mo) At asymposium "Application of mathematical methods to analyze heart rate" thereport of Baevski, Zemaichiche, Zatsiorxki, Parin showed that MSIHR providesbetter information to assess the status of the body function, particularly inprofession with high emotional stress

Recently, MSIHR method has been applied in Vietnam Studies of TaTuyet Binh, Nguyen Thu ha, Tran Thanh Ha, Nguyen Khac Hai, Nguyen NgocSon showed that intellectual stress and acute stress cause stress index toincrease and heart rate variation to decrease

1.2 Some neuropsychological functional indicators

Intelligence is the complex mental activity consisting of ability to learn, touse languages, to solve problems and ability to adapt to society

1.2.1 Intelligence assessment tests

The first scientist proposed the test ideas and coined the term "mental test"

as Francis Galton (1822-1911) After that the intelligence assessment tests were

alternately appeared such as: Binet-Simon (1905), Stanford-Binet test (1916),Wechsler scale (1939), Gille test (1944), Wisc test (1949) and Raven test(1960) Many intelligence tests have been widely used in countries around theworld such as: Russia, USA, Poland, Germany and France Raven test isofficially used by UNESCO to diagnose human intellect since 1960

In Vietnam, before 1980s of twentieth century, there have been someresearchs at Hanoi National University of Education applying intelligence tests

in evaluating learning outcomes of students such as: study of Tran Ba Hoanh,study of Nguyen Long From 1980s up to now, intelligence tests have beenwidely applied in our country The two facilities have made important

contributions in this field are Institute of Education Sciences of Vietnam andCenter for kid research in Hanoi These facilities have done many researchs onintellect of primary, secondary, high school pupils as well as universitystudents.

1.2.2 Attention, memory and thinking

Attention, memory and thinking of human beings are active, complexprocesses that have important roles in learning and processing information inmany different fields of activities In Vietnam, Tran Thi Loan found theincrease of attention ability of male and female pupils is also in the period ofincrease memory ability and in the period of development, improvement ofstructure and function of the brain The study of Lai The Luyen showed themost clear appearance and the highest rank of stress on students was hard tofocus and then hard to remember According to J Lazaus, stress causes memoryinjury, mental instability, inability to concentrate, hesitance, indecisive, lack ofattention, empty-headed These symptoms usually appear

1.2.3 Visual - motor reaction time, information processing speed

Information comes to human in various ways, through many chanels:vision: up to 90%, hearing, touching To evaluate the reaction of the body, forinstance: visual-motor reaction time, there has been a research of Z1 group inVietnam Military Medical University based on computer processing technique.From the result of measuring visual-motor reaction time they calculatedinformation processing speed Result of the study of Do Cong Huynh showedthat visual-motor reaction time lessen with age, greater age (less than 18)shorter reaction time This proven that information processing speed is gettingbetter due to age class The study of Ta Thuy Lan, Tran Thi Loan, Mai Van Hungdepicted similar result and reaction time in women was longer than that of men

1.2.4 Research on the relation between EEG and intellectual activity

Nervous-emotional stress induced by learning environment afterintellectual activities caused changes in the functional state of the nerve cells.These changes appear early and can be seen on EEG results Study of Vu DangNguyen showed EEG indicators changes depend on many factors causingnervous stress Tran Thi Cuc reported that amplitude of alpha waves decreased,while the frequency and index of beta waves increased proportional tointellectual capacity when thinking Thus the study of EEG changes at normal

and after intellectual work allows us to identify the intellectual performance ofeach individual.

1.3 Emotional stress

Emotional stress is a complex process related to social, psychological andphysiological factors According to Hans Selye, stress is the body's state arisingwhen strongly affected by factors from outside or inside the body In that state,body has to make sudden changes the biological activities, to ensurehomeostasis The non-specific responses of the body in a state of stress isconsidered as general adaptation syndrome GAS leads the body to a three-stageresponse: Alarm, Resistance and Exhaustion Hypothalamic-pituitary-adrenalaxis (HPA axis) system is the basic theory of GAS The activation of HPA andSympathetic Adrenal Medullary (SAM) leads to increase the body protectionactivities, mobilizes energy to help the body in responses to stimuli which causestress Physiological responses to stress are not only non-specific, but alsophysiological changes depending on environment, working conditions, socialfactors, stress experiences of individual Many hormones of the endocrineglands involve in reactions, in which cortisol and catecholamines are the mostimportant hormones and considered as the indicators of stress Learning stresscan be seen as a good study model of natural stress of human When studentsare stressed, the most clearly physical consequences of the students are difficult

to concentrate, easy to tense and inactive to work However, stress is not alwayscause negative impacts on the students The presence of stress sometimes isnecessary, which greatly affect the motivation and interest in their learning

CHAPTER 2 STUDY PARTICIPANTS AND METHODS 1.4 Study participants

Study participants are 600 students from 1st year to fifth year of full-timetraining course of general medical doctor in Thai Binh Medical University Wedid not choose 6th year students because they needed time to prepare forgraduation

Average age of the students has been shown in the table 2.1

Table 0.1 Tuổi trung bình của sinh viên các năm thuộc trường ĐH Y Thái Bình

Student

Age

1st year 2nd year 3rd year 4th year 5th year

X  SD 21,761,2 22,310,82 23,491,3 24,611,07 25,520,91

1 0

Selection criteria: Participants having BMI, pulse, blood pressure, hearing and

vision in the normal range, not suffering from acute or chronic diseases,especially cardiovascular, neurological and mental diseases; not using anyneuroleptics or stimulants for 3 days before and during the study time; beingvoluntary to take part in the study and willingness to follow all studyprocedures

1.5 Study methods

Analytical cross-sectional study

1.5.1 Sample size and sample selection

According to Phan Van Duyet, Le Nam Tra et al, samplie size for thestudies of biological indicators is as follows:

2 2 2

2 2

.

.

S t d N

N t S n

- In measuring ECG, mathematical statistical indicators of heart rate (MSIHR)and endocrine level, we selected d=10%, p=0,05, t=1,96 and calculated n=15

- We selected 30 students for each year (15 males and 15 females), hence, thetotal of the selected students from first year to fifth year was 30 x 5= 150(students) Having similar study results, these students were selected for thepurpose of evaluating some indicators before examination (control condition)and after examination In the total of 150 students we randomly chose 30students (15 males and 15 females) to evaluate the changes of blood hormonelevel in control condition and after the examination

1.5.2 Study indicators, measuring tools and methods

- Pulse rate in quiet status Use stopwatch

- Blood pressure in quiet status (mmHg) China sphygmomanometer was usedand standardized with mercury sphygmomanometer before measurement,using the Korotkov method Calculate Kerdo index

- Assessment of cardiovascular function and vegetative nervous system byusing mathematical statistical indicator of heart rate (Baevski RM et al.) onCadiofax 3 channels ECG machine of Japan.

- Assessment of intellectual capacity is determined by the ongoing test of Ravenframe types A, B, C, D, E

- Visual-motor reflex time and information processing speed is measured oncomputer using software of testing physiological psychology written by NgoTien Dung, Do Cong Huynh et al

- Attention ability was assessed by the method of "Arranging the jumbleddigits"

- Logical thinking ability was assessed by method of "Finding the digitpatterns"

- Short-term memory was assessed by the method of "Look and remember digits"

- Emotional stress was evaluated using Spielberger test

- EEG was recorded by Neurofax 9001 machine of NIHON KOHDEN, Japan

- Measuring serum cortisol levels on the Immulite 2000 machine of Siemensusing immunoassay method, in the Department of Biochemistry, NationalInstitute of Haematology and Blood Transfusion

- Measuring blood catecholamin levels using Smaznov method, in theDepartment of Biochemistry, Thai Binh Medical University

- 150 students were selected in the total 600 students, (30 students for eachyear unit) Data of ECG and 100 RR intervals of EEG were collected for the firsttime (10 students/time of recording ECG and EEG) In addition, blood of 30students was taken to measure hormone for the first time

Step 3 Measuring selected indicators of 150 students after the examination

These indicators were measured right after the exam We chose theexamination with 60 minutes length (3-4 credits) and 4 students per each class

of examination Each morning 3 classes had examinations; therefore, data ofonly 12 students were collected.

Time of measuring indicators was shown in the following diagram (Figure 2.1):

Figure 2.1 Study diagram of the students after examination

Pulse, blood presssure were recorded at 4 working stations; visual-motorreflex time were evaluated on 4 computers; 100 RR intervals of EEG wererecorded on 2 machines; blood sample for cortisol and catecholamin were alsotaken at 4 working stations Time of finishing all above indicators in 12 minutes(right after the exam), later, the students took attention, memory, thingking andemotional tests

* ECG were recorded after finishing another examination of 60 minuteslength We chose students who finished the examination after 45, 50, 55, 60minutes Time of ECG is 5 minutes after students out of examination room

* In order to avoid confounding factors, we measured indicators in controlcondition at the weekend, in the quiet room with fresh air Examination roomwas professionally designed, effects of outside factors were eliminated, airconditioned When indicators were measured after the exam, facilities werearranged next to examination room Room for measuring indicators was quietand air-conditioned

Data processing: Data were processed using biostatistical methods.

CHAPTER 3 STUDY RESULTS 1.6 Some cardiovascular indicators of Thai Binh medical University students

Results of cardiovascular indicators have been shown in table 3.1, 3.2 and figure3.1

Table 3.1 Some cardiovascular indicators of the students ( X ± SD)

Examination Pulse, Blood

pressure Visual-motor reflex time EEG

Blood sample

Diastolic blood pressure (mmHg) 70.717.56 67.778.19 <0.05

Table 3.1 showed no difference of pulse rate beetween male and femalestudents Systolic blood pressure (SBP) and diastolic blood pressure (DBP) ofmales was significantly higher than that of females (p<0.05) Kerdo index offemales was significantly higher than that of males (p<0.05)

1.1 Neuropsychological indicators of the students

1.6.1 Visual-motor reflex time and information processing speed

Results of visual-motor reflex time and information processing speed wereshown in the tables from 3.3-3.6 and figure 3.2

Table 3.4 Mean of visual-motor reaction time (VMRT) and information processing speed (IPS)

n=300

Females (B)n=300

of IPS in male and female students were not different (p>0.05)

1.6.2 Intellectual ability according to Raven test

Result of IQ score and its classification was shown in the tables from 3.9 and figures 3.3 and 3.4

3.7-Table 3.7 IQ scores of the students, ( X ± SD)

Sex

Year student

Males (A)n= 300

students were not significant (p>0.05).

Data in table 3.7 showed that IQ score of male and female students in eachyear were equivalent and there was no difference of IQ score between male andfemale students (p>0.05)

1.6.3 Logical thinking ability of the students

Table 3.13 Number of correct rows (Finding the digit pattern test) of the students

in each year,( X ± SD)

Sex

Year student

Males (A) n= 300

Result in the table 3.15 indicated that the number of recorded digits in maleand female students was similar This number of the fourth year students wasthe highest and remarkably higher than that of other students (p<0.05) Thenumber of recorded digits for male and female students was equal for each year(p>0.05).

1.6.5 Short-term memory of the students

Table 3.18 The number of recorded digits of the student ( X ± SD)

Sex

Year

Male A(n=300)

1.6.6 Emotional stress state

Result of evaluating emotional stress state was presented in the tables 3.22 and figure 3.12

3.20-Table 0.22 Emotional stress state of the students

Sex

Levels

Male n=300

Table 3.22 showed that emotional stress state of the students mostly weremoderate or severe level There was a relation between emotional stress levels

of male and female students The proportion of female students with severelevel or worse was significantly higher than that of male students (OR=0.6;95% CI: 0.4-0.8)

1.7 Some cardiovascular indicators of the students in control condition and after the exam

Results of pulse rate, blood pressure and mathematical statistical indicator

of heart rate on 100 beats ECG of the students in control condition and after theexam were presented in the tables 3.23-3.30 and figure 3.13

Table 0.23 Pulse rate, blood pressure of the students in control condition and

after the exams,( X ± SD)

(beats/

minutes)

control (1) 78.437.67 80.2111.23 >0.05 79.329.62examination

(2) 114.409.56 107.9310.69 <0.05

111.1710.62

DBP

(mmHg)

control (1) 70.677.55 65.207.32 <0.05 67.937.90examination

(2) 72.077.97 68.808.13 <0.05 70.438.19