Stroke A Journal of Cerebral Circulation

Transcription

1 A Jurnal f Cerebral Circulatin NOVEMBER-DECEMBER 1971 VOL. 2 NO. 6 Cerebrvascular Disease in the Bi-Racial Ppulatin f Evans Cunty, Gergia BY A. HEYMAN, M.D., H. R. KARP, M.D., S. HEYDEN, M.D., A. BARTEL, M.D., J. C. CASSEL, M.D., H. A. TYROLER, M.D., J. CORNONI, PH.D., C. G. HAMES, M.D. AND W. STUART, M.D. Abttract: Cerebrvascular Disease in the Bi-Racial Ppulatin f Evans Cunty, Gergia An epidemilgical study was made f cerebrvascular disease in a bi-racial Suthern cmmunity. The study ppulatin cmprised abut 3, men and wmen aged 15 t 75 years at the time f entry int the study. During the 87- mnth perid between the initial and secnd examinatins, 94 persns develped their first cerebrvascular event. The incidence f strke amng white men (4.7/1,/year) was almst fur times that in white wmen and mre than twice that reprted fr white men in ther sectins f the cuntry. The incidence rates f strke in Negr men and wmen were equal (5.8/1,/year). The risk factrs predispsing t strke in white men appeared t be severe hypertensin, besity, high hematcrit levels, and antecedent electrcardigraphical abnrmalities These factrs were nt as prminent amng the ther race-sex grups. The high incidence f cerebrvascular disease fund in this semirural ppulatin f Gergia supprts previus reprts f increased mrtality rates fr strke in this sectin f the cuntry and represents a unique situatin, the exact cause fr which remains t be determined. ADDITIONAL KEY WORDS strke mrbidity risk factrs race factrs epidemilgy ischemic heart disease Mrtality studies in the United States indicate that death rates frm cerebrvascular disease are greater amng Negres than Caucasians and higher in bth races in the Sutheastern sectin f the cuntry. Recent studies designed t authenticate these death Frm the Center fr Cerebrvascular Research, Duke University Medical Center, Durham, Nrth Carlina; The Divisin f Neurlgy, Emry Schl f Medicine, Atlanta, Gergia; The Department f Epidemilgy, University f Nrth Carlina, Chapel, Vl. 2, Nvember-Oecember 1971 Hill, Nrth Carlina; and the Department f Public Health, Evans Cunty, Gergia. This wrk was supprted by research grants frm U. S. Public Health Service NS-HE 6233 and HE

2 HEYMAN, KARP, HEYDEN, BARTEL, CASSEL, TYROLER, CORNONI, HAMES, STUART rates have shwn that the high mrtality fr cerebrvascular disease as appears n death certificates is prbably an accurate indicatin f an increased incidence f strke in the Sutheastern United States. 1-2 There is a need, therefre, fr further studies t determine the clinical and envirnmental factrs which may be respnsible fr this unique racial and gegraphical prblem. This reprt presents ur findings n the prevalence and incidence f cerebrvascular disease in Evans Cunty, Gergia, a small rural cmmunity with a 6% white and 4% Negr ppulatin. This reprt als describes the relatinship between cerebrvascular disease and the presence f cnditins thught t favr its develpment such as hypertensin, hyperchlesterlemia and besity. Previus epidemilgical studies f this cmmunity have described the sampling techniques and the sciecnmic and ppulatin characteristics f the study area. 3 The prevalence f ischemic heart disease and hypertensin as related t race, scial class and ccupatinal grups in this cmmunity has als been reprted. 4 ' B Methds The first survey examinatin f this study ppulatin (3,12 persns) was carried ut between August 1, 196, and June 1, 1962, and cnsisted f a histry f heart disease, strke and ther illnesses, a physical examinatin, electrcardigram, rentgengram f the chest, urinalysis, and labratry studies f the bld fr chlesterl and hematcrit. The secnd survey examinatin f this chrt was made by tw f the authrs (A. B. and S. H.) between August 1, 1967, and August 31, 1969, in a clinic established fr this purpse. During this seven-year t nine-year fllw-up perid (average 87 mnths), 32 persns had died and 252 had either migrated away frm the cmmunity r refused t return fr the secnd examinatin (table 1). The examina- TABLE 1 Disfribufin f Sample Ppulatin by Age and Sex in fhe Tw Survey Examinatins tin f the remaining 2,53 persns (9.9% reexaminatin rate) again cnsisted f a histry and physical and labratry studies, but als included a detailed questinnaire fr evidence f cerebrvascular disease and symptms f transient cerebral ischemia, a scilgical questinnaire, and a physical activities questinnaire. All persns with a histry r physical findings f any type f neurlgical disrder and particularly thse whse respnse t the questinnaire suggested transient cerebral ischemia r strke were referred t the neurlgists (A. H., H. K. and W. S.) fr further evaluatin. In additin, the recrds cntaining the questinnaire respnses f all 2,53 persns were reviewed by ne f the authrs (A. H.) and all persns having neurlgical symptms suggesting even a remte pssibility f cerebrvascular disease were called back fr neurlgical evaluatin. Examinatins were cnducted in the hme f the subjects wh were unable t visit the clinic because f disability due t strke r ther illnesses. Members f the subject's family were als interviewed if an adequate histry culd nt be btained because f aphasia, cnfusin r memry lss due t brain damage. A review was made by the neurlgists f the clinical recrds t cnfirm the cause f death in each f the subjects whse death certificate listed strke as a causative factr. Althugh autpsies were made in apprximately 3% f the 32 deaths during this interval, the brain was usually nt included in the pstmrtem examinatin. Spinal fluid and neurradilgical diagnstic studies were rarely part f the clinical examinatin during the subject's terminal illness. Fr these reasns, differentiatin f cerebral hemrrhage frm cerebral infarctin was generally nt pssible and n such distinctin has been made in the individual subjects. Criteria fr the diagnsis f cerebrvascular disease were established fr thse examined by the neurlgists and fr the cases listed as having a strke n death certificates. In bth grups, the subject was cnsidered t have a definite strke if there was a histry f sudden nset f aphasia r hemiparesis and the apprpriate neurlgical r Whit* mal* Whit* famed* N*gr mal* N**,r f*mei* Ttal Cases in first examinatin (196 t 1962) Died 196 t Migrated, refused, etc Cases in secnd examinatin (1967 t 1969) Percentage f eligible cases in secnd examinatin (1967 t 1969) 93.2% 94.3% 83.2% , ,53 88% 9.9% 51, Vl. 2, Nv*/nb*r-Dsc*/nb*r 1971

3 CEREBROVASCULAR DISEASE IN EVANS COUNTY, GA. physical abnrmalities were nted during the neurlgists' examinatin r during the subject's terminal illness. Arterigraphical, spinal fluid r autpsy findings f cerebral thrmbsis r hemrrhage were als cnsidered t be evidence f definite cerebrvascular disease. Subjects were classified as having a prbable strke if, at the time f his examinatin, the neurlgist btained a definite histry f sudden nset f aphasia r unilateral arm r leg weakness in vascular distributin, but n residual signs culd be fund n his examinatin. There were n instances in which the patient shwed residual neurlgical findings f a strke but denied a histry f this event. A diagnsis was made f death prbably caused by cerebrvascular disease if the death certificate listed strke as the underlying r cntributing cause and if the clinical recrds indicated that the terminal illness began with sudden lss f cnsciusness withut ther explanatin even thugh there was n mentin in the clinical recrds f hemiplegia r fcal neurlgical deficits. Patients with transient cerebral ischemia nly, i.e., neurlgical deficit less than 24 hurs' duratin, were nt included in the present study but will be cnsidered in a subsequent reprt. The prevalence rate f strke is the frequency and distributin f the disease fund in the 2,53 persns re-examined in 1967 t The incidence rate f cerebrvascular disease is based n the number f persns develping a fatal r nnfatal strke in the seven-year t nine-year fllw-up perid amng the 3,48 subjects wh were judged free f the illness at the initial examinatin in 196 t Results PREVALENCE OF CEREBROVASCULAR DISEASE During the secnd examinatin in 1967 t TABLE 2 < > 65* Ttal > 35 years All ages Age adj rate > 35 All ages l , 75 persns were diagnsed as having a definite r prbable strke (57 and 18 cases respectively). Of these, 53 had develped a strke during the interval between the tw survey examinatins, and 22 had a histry f cerebrvascular disease prir t the first examinatin in 196 t The ageadjusted rates were higher in men than in wmen and were higher in Negres than in Caucasians (table 2). Negr wmen had almst three times the rates f white wmen. Althugh the prevalence f strke generally increased with age, this tendency was nt as marked amng Negr men wh had mderately high rates in middle age (45 t 65 years). The diagnsis in almst every case was thught t be cerebral thrmbsis since thse with cerebral hemrrhage were nt likely t have survived t be included in this re-examinatin. One subject, hwever, a Negr male, gave a gd histry f subarachnid hemrrhage, and tw ther subjects (bth white men) had a diagnsis f cerebral emblism. These prevalence rates are nt likely t be in errr due t the inaccessability f persns wh refused re-examinatin r migrated ut f the cmmunity. This grup cnsisted largely f yung individuals, under the age f 35, in whm the likelihd f cerebrvascular disease is quite small. 6 INCIDENCE OF CEREBROVASCULAR DISEASE During the interval between the tw examinatins (an average f 87 mnths) cerebrvascular disease develped in 94 persns, in whm the diagnsis was definite in 65 cases and Ag-Specific Prevalence Rates f (per?,) Fund in Examinatin 1967 t J969 Whit* mltit* Whit fanll* Ngr nal* Ngr ftmd«aga at ttm* f Pp N Pp N Pp N Pp N first 9X111 uan COMI Rat* xam i Rat* ciai cas*«rat* xam «aj** Rat* *Only 11 persns were mre than 75 years f age, tw f whm had cerebrvascular disease , Vl. 2, Nv«mb»r-D«c»mb«r

4 HEYMAN, KARP, HEYDEN, BARTEL, CASSEL, TYROLER, CORNONI, HAMES, STUART 512 / 8 U» 961 ' 4) * (4 O * 14 _ D ae uc <u u _c u cc Spec D) 1 E z *S c ir J Z 5 Whit. 1 I ± S z. N at S CN CN ' IO CO w ruk Rat* i! w l at z e at w (at*. X a ** z^ n j! «i O; iq O io O OJO.CN ^ 3 c> O CN CO CO IO -^ "«t CO IS CN CN -* CN -<r CN ^ *~ c C> N. O r-oojlno CN CN -... l i <> CO CN N CO "O i CO O CO IB ii- C S ~ 5 1 -O -O ^j IA lf>. D = O Q- 2 «5.- i f5 < < s 3 > * e ll S cd O is E prbable in 29 thers (table 3). Fifty-three f the 94 cases were alive at the time f the secnd examinatin. The remaining 41 died shrtly after nset f their strke. Twenty-three ther subjects may als have had a strke in the 196 t 1967 interval, but were excluded frm this incidence table because f insufficient clinical infrmatin. They cnsisted f nine subjects wh were said t have had a strke, but died f ther causes. These cases were excluded because the clinical evidence fr the diagnsis f strke prir t death was prly dcumented, particularly amng the Negres. In 14 additinal subjects strke was listed n the death certificates as the underlying r cntributry cause, but the infrmatin which was available in their medical recrds was nt sufficient t cnfirm this diagnsis. The age-adjusted incidence rates fr cerebrvascular disease were highest amng the Negr men (6. per 1, per year). The rates fr white men, hwever, were nly slightly lwer (5.3 per 1, per year). It shuld be nted that these age-adjusted rates underestimate the Negr-Caucasian differences. The white male ppulatin has a higher prprtin f men aged 65 years and ver than the Negr ppulatin. At all ther ages the Negres have a higher incidence rate than the Caucasians and particularly at the 55 t 64- year age grup the Negres have a twfld excess. The rates fr white and Negr wmen were 1.7 and 5. per 1, per year respectively. After adjusting the cunty's age distributin t that f the 195 United States ppulatins, the estimated rates fr white men was 4.7, white wmen 1.2, and Negr men and Negr wmen 5.8 each. As shwn in table 3, the age-specific rates increased generally with advancing age. The white and Negr men, hwever, tended t have relatively high rates in their middle ages as well as in lder age grups. The slight decreases in the incidence f strke in white men age 55 t 64 and in Negr men 65 years r lder prbably represent artifacts resulting frm inadequate dcumentatin f the terminal illness f several men in these age-race grups. Althugh their clinical recrds suggested the pssibility f strke, the rigid criteria established in this study fr the diagnsis f cerebrvascular disease did nt permit their inclusin in the strke categry. Strk; Vl. 2, Nv»mb»r-Dec»mber 1971

5 CEREBROVASCULAR DISEASE IN EVANS COUNTY, GA. TABLE 4 Age-Specific Annual Incidence Rates (per 1,) fr in Five U.S. Ppulatin Studies Ag < Age adj rate All ages < Age adj rate All ages Ivans Cunty, a * * Mlddlisx Cunty, Cnn. White male * White female * Adjusted t age distributin U. S. ppulatin 195. Data frm references 7 t 1. Rch«t«r, Minn * * Pramlngham, MOM Mld- HJt.url COMPARISON WITH OTHER STUDIES The annual age-specific incidence rates fund in ur white study ppulatin are cmpared in table 4 with thse fund in ther small ppulatin studies. 7-1 It is apparent that the incidence f strke in white men fr all ages in Evans Cunty is mre than twice that fund in ther sectins f the cuntry. In cntrast, the incidence figures fr white wmen in ur sample ppulatin are cmpatible with thse fund in the ther studies. The nly published reprt f the incidence f strke in Negr men and wmen is the Mid-Missuri Survey 1 which is based n small numbers f cases. Nevertheless, the annual age-adjusted incidence rate btained in three rural cunties in Mid-Missuri was 5.9 (per 1, fr all ages) fr Negr men and 3.5 fr Negr wmen, figures similar t thse fund in the Evans Cunty Negr ppulatin. RISK FACTORS The incidence rates fr the initial episdes f either strke r ischemic heart disease during the 87-mnth study perid were determined in the sample ppulatin stratified accrding t the presence r absence f certain "risk" factrs bserved n entry int the study. An, Vl. 2, Nvember -December 197! analysis was made f the fllwing clinical and labratry characteristics: arterial bld pressure, serum chlesterl and hematcrit levels, electrcardigraphical findings, and bdy weight. The criteria fr the diagnsis f ischemic crnary heart disease have been described elsewhere, 6 and include patients with acute mycardial infarctin, angina pectris and ther clinical evidence f arterisclertic heart disease. RISK OF STROKE OR ISCHEMIC HEART DISEASE ACCORDING TO BLOOD PRESSURE The age-adjusted incidence f cerebrvascular r ischemic heart disease accrding t the level f bld pressure n entry int the study is shwn in figure 1. The study ppulatin was classified int three bld pressure categries: thse with nrmal r brderline pressures (equal t r less than 159/94); thse with mderate hypertensin (16 t 179/95 t 19); and thse with severe hypertensin (18/11 r greater). While the gradient between level f bld pressure and disease was clearer in the case f strke than in ischemic heart disease, hypertensin clearly increased the risk f bth diseases in all fur race-sex grups. 513

6 HEYMAN, KARP, HEYDEN, BARTEL, CASSEL, TYROLER, CORNONI, HAMES, STUART BLOOD PRESSURE ^±159/194 mm Hq H /95-19 and female, and fr Negr males thugh nt fr Negr females. RISK OF STROKE OR ISCHEMIC HEART DISEASE ACCORDING TO ELECTROCARDIOGRAPHICAL ABNORMALITIES In white men, the presence f antecedent electrcardigraphical abnrmalities (such as Q-waves, first-degree blck and ST-T abnrmalities) was assciated with a definite increase in susceptibility t strke as well as ischemic heart disease (fig. 3). A slightly increased risk f develping cerebrvascular disease was als bserved in Negr men and wmen with prir electrcardigraphical changes. The assciatin f electrcardigraphical abnrmalities with subsequent ischemic heart disease was als nted in white wmen, but nt in Negr men r wmen. RISK OF STROKE OR ISCHEMIC HEART DISEASE ACCORDING TO BODY WEIGHT The degree f verweight in ur subjects was determined by the Quetelet Index (weight in FIGURE 1 Risk f strke r ischemic heart disease accrding t bld pressure n entry age adjusted. In this figure and in the subsequent nes, the numbers within each bar indicate the ppulatin at risk in the denminatr and the cases develping either strke r ischemic heart disease in the numeratr. RISK OF STROKE OR ISCHEMIC HEART DISEASE ACCORDING TO SERUM CHOLESTEROL LEVELS The incidence f cerebrvascular disease in ur subjects accrding t their level f serum chlesterl n entry int the study is shwn in figure 2. Fr the entire age range, the percentage f men r wmen (Negr r Caucasian) develping strke was nt significantly different in the subjects with lw r intermediate chlesterl levels as cmpared with thse with high chlesterl levels (26 mg % r greater). An analysis f the chlesterl levels amng the strke cases in the yunger age grups (less than 55 years) likewise failed t shw any significant relatinships. In cntrast, there is a mdest relatinship between ischemic heart disease and elevated serum chlesterl levels fr Caucasians, bth male 514 NF n S Risk f level f WM CHOLESTEROL <2I9 mg.% FIGURE 2 strke r ischemic heart disease accrding t serum chlesterl n entry age adjusted., Vl. 2, Nvember-Dectmbtr 1971

7 CEREBROVASCULAR DISEASE IN EVANS COUNTY, GA. n I 3 * 1 11Q «9-7 5 m m..m ELECTROCARDIOGRAM j N EKG ABN EKG ABN I I1 m : : : w m I ? Heart Disease hematcrit levels, the number f cases f heart disease r strke in this grup was very small and the findings are nt cnsidered significant. It is apparent frm these analyses that the clinical and labratry characteristics favring the develpment f strke are nt always the same as thse assciated with the develpment f ischemic heart disease. Discussin The results f this study indicate that the incidence f cerebrvascular disease in this rural ppulatin f Sutheastern Gergia is cnsiderably higher than that in ther sectins f the cuntry. Similar high strke mrbidity rates have been reprted by Kuller and his assciates 1 in the white ppulatin f the nearby urban cmmunity f Savannah. These wrkers als nted a high rati f the incidence f strke in men t that in wmen in this area f Gergia as well as in Nrth Carlina. The 3 1 WM WF NM FIGURE 3 Risk f strke r ischemic heart disease accrding t EKG abnrmalities n entry age adjusted. punds divided by the square f the height in inches) and the results were stratified int thse with lwest, intermediate and highest weight by height indices. 11 The risk f develping strke r ischemic heart disease was increased in severely verweight white men and t sme extent in Negr men as well (fig. 4). White wmen with the highest indices als seemed t be mre susceptible t strke, but surprisingly this relatinship was nt evident in Negr wmen. An analysis f the pssible assciatin f Quetelet Index t ischemic heart disease in white and Negr females was nt cmputed because f insufficient infrmatin \ 4 & & WEIGHT Lwest Tertile Intermediate Greatest Heart Disese RISK OF STROKE OR ISCHEMIC HEART DISEASE ACCORDING TO HEMATOCRIT As shwn in figure 5, white men and wmen with very high hematcrit levels had an increased risk f develping strke r ischemic heart disease. Althugh a similar trend was present amng Negr wmen with very high, Vl. 2, Nvambtr-Dtcambtr Risk f strke r ischemic heart disease accrding t degree f besity (by tertiles) age adjusted. 515

8 HEYMAN, KARP. HEYDEN, BARTEL, CASSEL, TYROLER, CORNONI, HAMES, STUART HEMATOCRIT Risk f strke r ischemic heart disease accrding t level f hematcrit age adjusted. reasn fr the increased incidence f strke in the Sutheastern prtin f the United States is nt knwn, but there is evidence t suggest that the high prevalence f hypertensin in this area f the cuntry is ne f the mst imprtant etilgical factrs. 2 The significance f hypertensin and ther risk factrs in the develpment f strke has been described in ther prspective epidemilgical studies f cerebrvascular disease. Elevatin f arterial bld pressure, particularly, is knwn t be a majr predispsing factr in cerebral hemrrhage. In the study f Japanese men and wmen in Hirshima, hypertensin was assciated with a definitely increased risk f develping cerebrvascular disease. 12 As in the present study, the degree f hypertensin was fund t be a mre useful indicatr f strke than f ischemic heart disease. In the Framingham ppulatin, hypertensin increased the prbability f develping 516 cerebral thrmbsis abut fivefld ver that f nrmtensive individuals. 18 In the Ls Angeles study f male city emplyees reprted by Chapman, 14 there were 2% strkes amng the nrmtensive ppulatin as cmpared t 9% amng thse with hypertensin, the increased risk being mre apparent in cerebral hemrrhage than in cerebral thrmbsis. Our bservatins n the assciatin f hyperchlesterlemia with vascular disease have als been cnfirmed in ther studies. Althugh high serum chlesterl levels are recgnized as a risk factr in crnary artery disease, particularly in the yunger age grups, its relatinship t the develpment f cerebrvascular disease is less well established. Chapman 15 reprted little r n increase in the risk f strke assciated with high serum chlesterl levels except in thse withut hypertensin. In the Framingham ppulatin there was an increase in the incidence f strke assciated with elevated serum chlesterl levels nly in subjects under the age f In lder age grups, elevated lipid levels are nt reliable indicatrs f susceptibility t either strke r heart disease. Althugh the Hirshima ppulatin generally had lw chlesterl levels, hyperchlesterlemia (values exceeding 22 mg %) was fund t be assciated with added risk f strke in bth men and wmen, particularly the latter. 12 Our bservatins n the relatinship f strke t antecedent electrcardigraphical abnrmalities were als nted in the Framingham study. The presence f left ventricular hypertrphy, intraventricular blck and nnspecific electrcardigraphical abnrmalities were assciated with a very high risk f cerebral infarctin in the Framingham ppulatin. 18 Similarly, in Japanese men and wmen, electrcardigraphical evidence f left ventricular hypertrphy (as well as cardiac enlargement by radigraphical examinatin) increased the risk f strke almst three t five times. 12 Extreme besity was fund t be assciated with an increase in the risk f strke in men and in white wmen in the Evans Cunty ppulatin. Similar findings were btained in bth the Framingham and Japanese ppulatins. 12 ' 1S The results f the Ls Angeles study als suggested an increased risk f cerebral thrmbsis with increasing weight. 115 Strkt, Vl. 2, Nv«mfa«r-D«c»mber 1971

9 CEREBROVASCULAR DISEASE IN EVANS COUNTY, GA. Only a very few studies have been reprted n the relatinship f high hematcrit levels t subsequent develpment f strke. It is ntewrthy that Japanese wmen with elevated hemglbin r hematcrit levels seemed t have an increased risk f develping a strke, but n significant assciatin was fund in Japanese men. 12 In the present study, there was sme evidence t indicate that high hematcrit levels were assciated with increased susceptibility f strke in white and Negr men. The incidence f ischemic heart disease may als be higher in the white men and wmen with elevated hematcrit levels n entry int the study. Many f the factrs which were fund in this study t increase the susceptibility t strke have als been reprted in ther studies f cerebrvascular disease. Our bservatins n the incidence f strke, hwever, differ frm thse nted in ther areas f the cuntry. In the Nrtheastern and Mid-Western sectins f the U. S., fr example, the incidence f strke in white men is similar t (r perhaps nly slightly higher than) that in wmen, whereas the rates fr ischemic heart disease in men is usually several times that fund in white wmen. 7 ' 1 In ur sample ppulatin, the incidence f strke in white men was almst fur times that f white wmen, a rati even greater than that nted fr ischemic heart disease in this cmmunity. Despite this similarity in the incidence f strke and heart disease, the risk factrs predispsing t strke were nt necessarily applicable t heart disease. It is ntewrthy in this regard that relatively few f ur cases f ischemic heart disease develped cerebrvascular disease, a phenmenn emphasized particularly in the Framingham study and frequently bserved in clinical practice. The type f strke mst cmmnly assciated with ischemic heart disease is that caused by athersclertic cclusive disease f the extracranial prtin f the cartid r vertebral arteries, r by cerebral emblism assciated with cardiac arrhythmias, valvular disease r mural thrmbus due t recent mycardial infarctin. It is ur clinical impressin that mst f the subjects fund t have strke n neurlgical examinatin had intracranial vascular disease. The usual manifestatins f extracranial cartid disease such as a histry f transient cerebral ischemia and Strk; Vl. 2, Nv»mb»r-D»c«mber 1977 the presence f cartid bruits were nted in nly very few cases. The pssibility that a specific type f strke accunts fr the race, sex and area differences within the United States has been ffered by Kuller and his assciates. 1 They suggested that ppulatins characterized by a high prevalence f hypertensin and lw lipid levels shuld have a higher rati f intracranial t extracranial vascular disease. This particular cmbinatin f risk factrs was a cmmn pattern in ur strke cases and tends t supprt the hypthesis suggested by these wrkers. References 1. Kuller L, et QI: Natinwide cerebrvascular disease mrbidity study. 1: (Mar- Apr) Nefzger MD, Achesn RM, Heyman A: mrtality amng U. S. veterans in Gergia and five western states. T be published 3. McDnugh JR, et al: Cardivascular disease field study in Evans Cunty, Gergia. Public Health Rep 78: , McDnugh JR, et al: Crnary heart disease amng Negres and whites in Evans Cunty, Gergia. J Chrn Dis 18: , McDnugh JR, et al: Bld pressure and hypertensive disease amng Negres and whites. Ann Int Med 61 : , Crnni JC et al: Study design and methds: The Evans Cunty Study. Arch Int Med (In press) 7. Eisenberg H, et al: Cerebrvascular accidents. Incidence and survival rates in a defined ppulatin, Middlesex Cunty, Cnnecticut. JAMA 189: , Whisnant JP, et al: Natural histry f strke in Rchester, Minnesta, 1945 thrugh : (Jan-Feb) Framingham study: An epldemilgical investigatin f cardivascular disease. Washingtn, D.C., U.S. Gvernment Printing Office, Eckstrm PT, et al: Epidemilgy f strke in a rural area. Public Health Rep 84: , Khsla T, Lwe CR: Indices f besity derived frm bdy weight and height. Brit J Prev Sc Med 21: , Jhnsn KG, et al: Cerebral vascular disease in Hirshima, Japan. J Chrn Dis 2: , Kannel WB, et al: Vascular disease f the brain epidemilgic aspects: The Framingham study. Amer J Public Health 55: , Chapman JM, et al: Epidemilgy f vascular 517

10 HEYMAN, KARP, HEYDEN, BARTEL, CASSEL, TYROLER, CORNONI, HAMES, STUART lesins affecting the central nervus system: 15. Chapman JM, et l: Risk factrs and the The ccurrence f strkes in a sample develpment f strke in the Ls Angeles study ppulatin under bservatin fr cardivascu- area. Abstract. Cuncil n Epidemilgy, lar disease. Amer J Public Health 56: , American Heart Assciatin Meeting, New Orleans, March 4, , Vl. 2, Nv«mb«r-Dec*mb«r 1971