Trần Bình Thắng, Võ Văn Thắng, Michael P Dunne, Trần Quỳnh Anh.Nghiên cứu năm 2013. Hội nghị khoa học quận Thủ Đức, thành phố Hồ Chí Minh. Y học thực hành (880).Nghiên cứu mô tả cắt ngang về trầm cảm, ý định tự sát và lo âu ở sinh viên đa khoa Y1, Y3, Y5 trường Đại học Y Dược Huế sử dụng bộ công cụ CESD.Các yếu tố liên quan sử dụng hồi quy tuyến tính đa biến rút gọn (Linear Multiple Regression).
TRAM CAM, Y DINH TV' SAT vA LO AU (y SINH VIEN Y KHOA MIEN TRUNG VII;T NAM: TY Le vA cAc YEU TO LIEN QUAN TRAN SINH THANG IT NghifH] c~u SiPc kh6e ct;mg dong, TrU'iYng f)H Y DLJ'ClC Hue . VO VAN THANG - TrU'iYng f)~i h9C Y DLJ'ClC Hue MICHAEL P DUNNE - f)~i h9C Cong ngh~ Queensland, Uc TRAN QUYNH ANH - f)~i h9C Y Hil NOi TOM TAT M~c tieu: Nhi~u tr.U'&ng d<;lihoc iren the giai c6 nniem VI,1 cham s6c sinh vien kll ca nhO'nfj sinh vien c6 nhO'ng kh6 khan ve tam ty. Te! Vi~t Nam va cac nuoc vung Mekong khac, cac djch VI,1 tir van va cham s6c s(PC; khOe t6ng quat cho sinh vien con rat it. Nghien cuu nay nhiim cet thi~n b~ng chl.fng v~ dau hi~u trem cam va y tU'&ng tl)' sat dll giai tbieu cac diet: VI,1 cham s6c s(PC; kh6e tam th~n cho sinh vien tnrcnq y. PhU'O'ngphap nghien CLPu:Nghien cou dt ngang vo! 267 sinh vien bee s9 da khoa truong y nem thLf nMt, ttur ba va thl.f nem, nghien cou tei truong f)<;lihoc Y DuQ'CHue. Cec lap auoc chon ngau nhien, tat ca sinh vien cac lap duQ'C Il)'a chon thu(jn tien tham gia nghien cou nay. Bang h6i dau ten, tir di~n duQ'c dung dll kMo sat cac yeu to enn huang ntur te: ganh n~ng hoc t(jp, cac sir ki~n gay stress doi voi ooi song ca nnen sinh vien, nhO'ng tienn vi nguy co anh huang den sue khOe va Il)'a chon ngh~ nghi~p. Cec mo hinh hai quy ae bien duQ'c dung dll kMo sat moi quan M giO'a cac bien doc I~p va trem cam va 10au, killm soet cac yeu to nhi{JU. Ket qua: mot trong seu sinh vien billu hi~n toi thieu c6 mot so tri~u ch(fng trem cem va/ho~c 10au. Trong nem voe qua sinh vien c6 y dinh, c6 ke hoech va co g~ng iir tir chiem 10,5%, 4,5% va trong thai gian g~n day la 5%. ceo yeu to lien quan den trieu cturnq trem cem bao gam giai tinh ntr, cha me Iy dj hoec Iy than, ngh~ nghi~p cue me (nong dan), hoc trong thai gian dai, oil3m hoc thap, cac sir ki~n gay stress trong 12 thang vtre qua va b! eo buoc Il)'a chon ngh~ y (do nhO'ng eo luc ben ngoai). Ket lu~n: M~c du oay la mot cM d~ mo! trong h~u Mt cac truong d<;lihoc a Vi~t Nam, nghien cuu nay khtJng dinh l<;linhO'ng xu huang menq tinh quoc te. Nhi~u sinh vien cniu dl)'ng ganh n~ng tam th~n nghiem tronq. 10% c6 y djnh tl)' tir trong nsm voe qua, Y2 c6 y dinh tir tir cia ten ke noecn. Cec yeu t6 lien quan voi soc khoe tam th~n kern bao gam ganh n~ng hoc t(jp va viec dang ky vao nqenh Y kh6ng pMi te mong muon cue ho (thU'&ng la dll aep tei sir mong dQ'icue bo me). TCPkh6a: Tr~m cem, 10au, y tU'&ng tl)' sat. SUMMARY Objectives: Universities worldwide have a duty to care for their students, including those who suffer psychological difficulties. Unfortunately in Vietnam and some other Mekong countries, there are few functioning counseling and general health services for university students. This study was undertaken to improve the evidence base for the introduction of mental health services for students in medical universities. Methods: A cross-sectional survey was conducted with 267 undergraduate medical students in the first, third and fifth years of their course in April 2013 at Hue University of Medicine and Pharmacy. Classes were randomly selected and all students attending classes on survey days participated. The anonymous, self-completed questionnaire explore a wide range of potential influential factors, such as study burden, stressful life events, health risk behaviors and career preferences. Multivariable regression models were used to examine associations between the independent variables and depression and anxiety, controlling for confounding factors. Results: Approximately one in every six students reports at least some symptoms of depression and/or anxiety. Past year suicidal thoughts, planning and attempts were reported by 10.5%, 4.5% and 1.5% respectively. Factors associated with depression symptoms included female gender, parental divorce/separation, occupation of mother (farmer), long study hours, low GPA, multiple stressful life events in the past 12 months, and studying medicine as an unwanted career choice (due to external pressure). Similar though fewer factors correlated with anxiety, including female gender, minority ethnicity, multiple stressful life event in the past 12 months, illness in the past 4 weeks, and occupation of mother (farmer). Conclusions: Although still a new topic in most universities in Vietnam, this study confirms trends observed worldwide. Many students carry with them a significant mental health burden. In this study for example, about 10% had thought about suicide in the past year, and half that number had made a plan. Factors significantly correlated with poor mental health included study burden and enrolment to study medicine that was somewhat against their own preference (usually to meet parental expectations). Further research relevant to mental health promotion should focus on the relationships between the student and family factors,academic burden and recent stressful life events. Keywords (3-5): Depression, anxiety, suicidal behaviors. 216 YHTH (880) - HOI NGH! KHOA HOC B~NHVI~N QUAN THO oec TP. H6 CHI MINH I.D~TVAND~ Sinh vien dai hoc la nhCrng. ngll'ai tre phai doi mat voi kho khan v~ earn xuc va hanh vi cua qua trlnh chuyen doi hi vi thanh nien den tuoi trU'6>ng thanh, d$c blet la thai gian anh hll'6>ng cua cac ap il,l'c do. Trang so cac sinh vien dai hoc, sinh vien Y khoa thll'ang chiu nhieu ap il,l'c hoc tap cao hon so voi cac nqanh khac b6>ithai gian keo dai 6 narn va chuonq trlnh dao tao kha n$ng. 3 nquyen nhan gay nen cac ap lu'c Ion cho sinh vien Y khoa nhu cac ky thi, Ill'O'ng kien thuc Ion v~ cac linh vue danh cho bac sy da khoa va rat it co thai gian de xem kien thuc da hoc. NhCrng thanh to do qop phan lam cho cac sinh vien qua tai cac kien thuc can hoe va van d~ thi cu. TCr nhCrng van d~ do dan . den lam cho cac sinh vien earn thay hut hang, that voriq, nhCrng canq thang theo suet ho trong 6 nam, Trang cac nghien ciru gan day chi ra rang ty 1$v~ cac 10au tam 1'1(10 I~ng tam 1'1la mot khai niern rong bao gom 10au, cang thang, tram earn va cac van d~ lien quan den sue kh6e tam than 6> .sinh vien dai hoc 6>cac truonq d<;lihoc va cac vien tren the gioi tren the gioi dao dong trong khoanq 21 den 56% [13]. a nhieu nuoc, hon mot phan tu tre thanh thieu nien da tCrng co cac trieu chling tram earn va khoanq 15%-20% thinh thoanq hoac thuonq xuyen co 'I nghi v~ tl,l' sat. TY 1$ rieng v~ tram earn SLPdunq thang do CESD (diem cat 16) tronq 1 nghien cuu tong quan he thong dua vao thang do CESD cua tac gia Ahmed K. Ibrahim va cong su cho thay rang ty 1$tram earn trong khoanq 35,2 - 38,4 [8] hay nqhien cuu tong quan h$ thong khac tren sinh vien Y khoa My va Canada cho ty 1$ 15 - 19% [7]. Cac van d~ v~ 10 au, trong nqhien cuu cua Chandavarkar va cs chi ra rang co toi 11,5% bi roi loan 10 au trong qua trlnh hoc [5] va tac gia Smith va cs 11314.4% [11]. Tl,I' tli dll'O'c biet den nhu 113mot trong 3 nquyen nhan dan dau tli vong 6>doi tU'O'ng vi thanh nien va ngll'ai tre tuoi. Doi voi sinh vien Y khoa thl mot vai nqhien ciru 6> chau A (Han Ouoc, Trung Ouoc va Hong Kong) 6> ngll'ai tre tuoi cho thay rang ty 1$co 'I dinh v~ tl,J'tli tren 20%, trong mot nghien cuu cua nhorn tac gia Blum R va cs thuc hien 6>Viet Nam, Trung Ouoc va Dai Loan thl ty 1$ co y dinh va co g~ng tl,l' tli chung 6>3 quoc gia 1138,4% va 2,5% [4]. Trong khao sat SAVY2 co do tuoi tCr 14-25 ty 1$co hanh vi tl,J' tli 11312,21 % trong khao sat SAVY 1 113 5,28% [9] hay mot vai nghien cliu gan day khac 6> cac khu Vl,l'CHa Noi, Hai Dll'O'ng, Tp HCM ty 1$d~u dll'oi 10%. NhCrng phan tich tren d~u minh chling cho thay nhCrng ganh n$ng cua van d~ slic kh6e tarn than IEm nhCrng ngll'ai tre tuoi d$c bi$t doi tll'O'ng sinh vien y khoa, no co the dan den nhCrng h~u qua lau dai, nhCrng anh hll'6>ng v~ ngh~ nghi$p tll'O'ng lai cua hO. Cac yeu to qua tong quan y van cho thay rang cac yeu to nhu gia hoc 1'1thuyet, lam sang , cac yeu to ca nhan (gioi, narn hoc), gia dlnh (ngh~ nqhiep, Sl,J'ky vonq cua bo me, hen nhan bo me) va cac va chan trong thai gian gan day dll'O'c ghi nhan nhu cac yeu to lien dean co lien quan gan den cac van de sue kh6e tam nhu tram earn, 10au va tl,l' tli. Tuy v~y, theo cac y van thl nqhien cuu tren sinh vien Y khoa con rat it va han che 6>Viet Nam, d$c biet tren doi tll'O'ng sinh vien Y da khoa. Cac dich vu cham soc, tu van ve van de sue kh6e tam tri 6>sinh vien dai hoc con la cau h6i Ion cho chinh sach va cac dich vu cham see sue kh6e tam tri. Nghien cuu nay nha"m rnuc dich tlm ra cac bang chling co tinh khoa hoc nharn cai thien va xay dl,l'ng cac dich vu cham soc sue kh6e cho sinh vien trU'ang Y khoa 6> Mien trung noi rieng va cac sinh vien dai hoc, cao dang _ noi Chung. Nghifm ClPU v60i muc W~U xac dinh ty 1$ tram earn, 10au va 'I dinh tl,l' tli 6>sinh vien Y khoa va xac dlnh cac yeu to lien doan lien quan den tram earn va 10au. II. PHU'O'NG PHAp NGHIEN ciru 2.1. Thi~t k~ nghifm ClPU: Day la mot nghien cuu cat ngang, theo do, cac doi tuonq nqhien cuu dll'O'c ph6ng van tai mot thai diem. 2.2.ThOi di~m nghien cuu: tCr thanq 3 den thanq 4 narn 2013. 2.3. Dia ban nghien ClPu: tal trll'ang d<;lihoc Y Dll'O'C Hue, thanh pho Hue, Mien trung Vi$t Nam. Cong trlnh nghien cuu duoc su phe chuan cua hQi dong Y dlic true thuoc trU'ang D<;Ii hoc Y Dll'O'C Hue. Tat ca cac doi tll'O'ng tlnh nquyen tham gia vao chuonq trlnh nqhien cuu deu dll'O'c giai thich rnuc lieu va phuonq phap nghien cuu theo dung quy dinh cua To chuc Y te the gioi va ky vao ban tl,l' nquyen, 2.4. D6i tU'Q'ng nghien ClPu: Doi tll'O'ng nghien cuu dll'O'c chon ngau nhien cac khoi lop Y da khoa nam 1, nam 3 va nam 5. Chung toi lien lac cac em duoc ngoi each biet 1 ban va dien phieu dll'oi Sl,l' hll'ong dan va giam sat cua 3 can bo nghien ciru va tro 1'1nghien cuu Dua vao y van ty 1$tram earn thanh nien Viet Nam. Chung toi tinh duoc doi tll'O'ng nghien cliu la 267 ngll'ai de ll'oc Ill'O'ng ty 1$ voi khoang tin c~y 95%. 2.5. PhU'O'ng philp thu th~p thong tin: Mot bO cau h6i tl,l' dien dll'O'c thiet ke de thu th~p cac dCr li$u lien quan nhll' thong tin Chung: tuoi, gioi, khoi lop, hO khau trU'oc khi nMp trll'ang (thanh thi/nong thon), nghe nghi$p cua cha/me. Ap dl,lng Thang do cua Trung tam nghien ClPUdich te hQc (CES- D: The Center for Epidemiological Studies- Depression Scale) thu9C Trung tam phOng ngCra va kiem soat b$nh t~t cua My da dll'O'c kiem dinh va sli dl,lng rat nhieu trong cac dieu tra cong dong voi doi tll'O'ng vi thanh nien 6>nhieu quae gia tren YHTH (880) - HOI NGH! KHOA HQC B~NH VI~N QU';N THO DUC TP. H6 CHf MINH 217 thlP 5, cac sinf vien c6 nhieu trai nghi$m tot hon de lPng ph6 v6'i nhCrng cang th~ng trong hoc tap, KE qua nay tU'O'ngtl,J'v6'i ket qua cua Surbhi Sidana nqhien ClPUtren sinh vien Y khoa An f)o [12]. 3.2 Tj I~ 10 au - tt,J'tt.'P La au: Theo nh6m tac gia Chandavarkar va Cs chi ra r~ng c6 t6'i 11,5% bj roi loan 10 au trong qu trlnh hoc [5] va tac gia Smith va cs 11314.4% [11]. Theo diem cat thang diem 10au ;:: 26 thl ty 1$ 10 a chung trong nqhien ClPUnay (18,73%) cao hon. TY 1$theo gi6'i va khoi lop duoc m6 ta b~ng bieu d6 nh tram earn. Y tU'&ng tt,J'tir: Suy nghr tu lit 2.26 ~ Len k~ hoach I\t lit cs gAng tv tit l~ 12 10 . S () 4 12.03 o Bitw cia 2: Phan bo tj I~ sinh vien co y cijnh tt,J'tt.'Ptheo gi(Yi Thea cac nqhien ClPUcua mot nh6m tac gia nqhien ClPUtren doi tU'Q'ng vj thanh nien va thanh nien v ty 1$c6 y dinh tl,J'tLY(y cac nuoc Han Ouoc, Trung Ouoc, f)ai Loan ty 1$ deu tren 20% so sanh voi nghien ClJU(y Viet nam duoc thuc hi$n (y Ha NOi, Tp. H6 Chi Minh, Hai DU'O'ng ty 1$ nay chi dao don dU'6'i 10%. Ket qua nqhien ClPUcua chunq t6i cOng 113mot minh chlPng ro rang khi h6i sinh vien trong von 12 thanq qua va ty 1$tra l6'i co chiern 10,49%. Khi h6i ve lap ke hoach thl c6 toi 4,49% va 1,50% cac sin vien da tung co gc)ng tl,J'tLY. 3.3. cae y~u t6 lie':1 quan Bang 1:,M6 hinh h6i quy tuven tfnh da bien rut qon (Linear Multiple Regression Bien so Gia tri bien Tram earn La au 13 SE 13 SE Gi6'i Nam Ref - NO> 0,28* 0,10 0,12* 0,03 Song cunq voi nhau Ref - Hon nhan bo me Ly d] /Ly than 0,57* 0,36 G6a -0,13 0,21 CB Ref - Ref - Tl,I'lam chu -0,07 0,17 0,02 0,05 Nghe nghi$p me Nonq can 0,27* 0,12 0,08* 0,03 That nqhiep 0,48 0,42 0,08 0,11 NOitro -0,01 0,14 0,03 0,04 Gi6'hoc Iv thuvet & 16'0 Gi6' hoc Iv thuvet & 16'0 -0,01 0,01 <5,5 ref 5,5-6,4 -0,65 0,45 £)iemtong ket narn hoc 6,5-7,4 -0,86 0,48 7,5-8,4 -0,95* 0,48 8,5-8,9 -0,65* 0,52 NhO>nQSl,I'kien cane thane tronq cuoc sonq -0,11* 0,03 -0,02* 0,01 Tatca 2,42 0,68 Tham choi rr-'- 2,33* 0,68 Mot it*\'-) 2,49 0,67 NO'icono tac sau ra truono 0,60 0,26 KhOngbi dau gl Ref - B]daudau/dau lU'ng/dau C6 dau mot chut 0,08* 0,03 bl,mg/dau tay/dau chan C6 dau vua phai 0,11* 0,04 gaycantr& cong viec Dau kha kha 0,13* 0,05 Dau nohiern trono 0,17 0,14 Ref: tham chi~u; *: p co y nghia thong ke voi trurc y nghia <0,05. {3: M so h6i qui tuy~n tint: ChL chu~n h6a; SE: sai so chuen YHTH(880)- HOI NGH! KHOA HOC B~NH VI~N QUAN THO m1c TP. H6 CHI MINH 2 Trong phan tlch hoi quy tuyen tlnh don bien chung tei li$t ke ra dU'Q'c 20 bien so co y nghia thong ke: Trong me hinh hoi quy tuyen tlnh da bien (rut qon tren) chi ra cac yeu to lien quan den tram earn: gi&i tlnh (nu'); hen nhan bo me (Iy dilly than); nghe ~hi$p me (neng dan); diem tong ket narn hoc; nhCl'ng Sl,l' ki$n cang th~ng trong cuoc song, tharn choi (thinh thoanq). Trong me hinh hoi quy tuyen tfnh da bien chunq tei cang dua vao 18 bien so c6 y nghia trong me hinh don bien va ket qua rut ra tli me hinh tren cac yeu to lien quan den 10 au: gi&i tinh (nu'); nghe nghi$p me (neng dan); nhCrng sv kien cang thang trong cuoc song, tharn choi (thinh thoanq); bi dau dau/dau lU'ng/dau bunq/dau tay/dau chan gay can treYconq viec (c6 dau mot chut, c6 dau vua phai, dau kha kha). Ket qua tli me hinh cho thay rang cac yeu to gia dl nh va nhCrng su kien sang chan trong 12 thanq qua c6 lien quan den tram earn va 10au. Ket qua nghien cuu nay cung tuonq dong voi mot so nghien cuu hien nay tren the gi&i [10]. Tuy nhien trong boi canh cua Viet Nam thl can c6 nhieu nqhien cuu sau hon di sau vao van de nay. Cac yeu to ve su mong dQ'i tli gia dinh ve nqanh nghe, mac du c6 y nghia don bien nhtrnq trong me hinh da bien thl kheng c6. M~c du v$y, day la mot trong nhCrng han che cua nqhien cuu khi cO' mau nho, can cac nqhien ctru tU'O'ng lai can di sau hon. IV, K~T LuAN - TY 1$ tram' earn, 10 au chiem ty 1$ 18,73% eY sinh vien Y khoa. Ty 1$ sinh vien c6 y dinh tl,l' tCP: Suy nghi tl,l' tCP10,49%; ve lap ke hoach 4,49% va . 1,50% da tling co gcf!ngtl,l' tCP - Cac yeu to lien quan den tram earn: gi&i tlnh (nCr); hen nhan bo me (Iy dilly than); nghe nghi$p me (neng dan): diem tong ket narn hoc; nhCrng str kien cang th~ng trong cuoc song. Cac yeu to lien quan den 10 au: gi&i tinh (nCr); nghe nqhiep me (nonq dan): nhCrng Sl,l' kien cang th~ng trong cuoc song; bi dau dau/dau lU'ng/dau bunq/dau tay/dau chan gay can treYceng viec. TAl ueu THAM KHAo 1. Nguyen D(Pc Thanh, Le Cl,I' Linh (2010) "Gia tr], do tin c$y cua thang do tram earn cua vi thanh nien va thanh nien va mot so yeu to lien quan t<;3i huyen Chi Linh, Hai DU'O'ng narn 2006 ". Tf)p chi Y ttJ Gong Gong 33 (26), tr. 33-41. 2. Nguyen Thanh HU'O'ng, Le va Anh, Michael Dunne (2007) "Gia tri va do tin c$y cua hai thang do tram earn va 10 au sCPdl,lng nqhien cuu cong dong v&i doi tU'Q'ng vi thanh nien ". Tf)p chi Y ttJ Gong cong 25 (7), tr. 25-31. 3. Khadijah Shamsuddin, Fariza Fadzil, Wan Salwina Wan Ismail, Shamsul Azhar Shah, Khairani Omar, Noor Azimah Muhammad, Aida Jaffar, Aniza Ismail, Raynuha Mahadevan (2013) "Correlates of depression, anxiety and stress among Malaysian university students". Asian Journal of Psychiatry, 6 (4),318-323. 4. R. Blum, M. Sudhinaraset, M. R. Emerson (2012) "Youth at risk: suicidal thoughts and attempts in Vietnam, China, and Taiwan". J Adolesc Health, 50 (3 Suppl), S37-44. 5. U. Chandavarkar, A. Azzam, C. A. Mathews (2007) "Anxiety symptoms and perceived performance in medical students". Depress Anxiety, 24 (2), 103-11. 6. Vuong Diem Khanh Doan (2011) What Explains the Association between Socioeconomic status & Depression in Vietnamese Adults? , Faculty of Health, Queensland University of Technology, 7. L. N. Dyrbye, M. R. Thomas, T. D. Shanafelt (2006) "Systematic review of depression, anxiety, and other indicators of psychological distress among U.S. and Canadian medical students". Acad Med, 81 (4), 354-73. 8. A. K. Ibrahim, S. J. Kelly, C. E. Adams, C. Glazebrook (2013) "A systematic review of studies of depression prevalence in university students". J Psychiatr Res, 47 (3), 391-400. 9. M. T. Le, H. T. Nguyen, T. D. Tran, J. R. Fisher (2012) "Experience of low mood and suicidal behaviors among adolescents in Vietnam: findings from two national population-based surveys". J Adolesc Health, 51 (4), 339-48. 10. X. C. Liu, S. Oda, X. Peng, K. Asai (1997) "Life events and anxiety in Chinese medical students". Soc Psychiatry Psychiatr Epidemio/, 32 (2), 63-7. 11. C. K. Smith, D. F. Peterson, B. F. Degenhardt, J. C. Johnson (2007) "Depression, anxiety, and perceived hassles among entering medical students". Psychol Health Med, 12 (1),31- 9. 12. 1 Jugal Kishore Surbhi Sidana, 1 Vidya Ghosh, 1 Divyansh Gulati, 1 RC Jiloha, 2 and Tanu Anand 1 (2012) "Prevalence of depression in students of a medical college in New Delhi: A cross-sectional study". Australasian Medical Journal, 5 (5), p. 247-250. 13. M. S. Yusoff, A. F. Abdul Rahim, A. A. Baba, S. B. Ismail, M. N. Mat Pa, A. R. Esa (2013) "Prevalence and associated factors of stress, anxiety and depression among prospective medical students". Asian J Psychiatr, 6 (2), 128-33. 220 YHTH (880) - HOI NGH! KHOA HOC B~N~ VI~N QUAN THO eoc TP, H6 CHr MINH . ngll'ai tre tuoi. Doi voi sinh vien Y khoa thl mot vai nqhien ciru 6> chau A (Han Ouoc, Trung Ouoc va Hong Kong) 6> ngll'ai tre tuoi cho thay rang ty 1$co 'I dinh v~ tl,J'tli tren. TRAM CAM, Y DINH TV' SAT vA LO AU (y SINH VIEN Y KHOA MIEN TRUNG VII;T NAM: TY Le vA cAc YEU TO LIEN QUAN TRAN SINH THANG IT NghifH] c~u SiPc kh6e ct;mg dong, TrU'iYng f)H Y DLJ'ClC Hue narn va chuonq trlnh dao tao kha n$ng. 3 nquyen nhan gay nen cac ap lu'c Ion cho sinh vien Y khoa nhu cac ky thi, Ill&apos ;O& apos;ng kien thuc Ion v~ cac linh vue danh cho bac sy da khoa va