Factor V Leiden (resistance to activated protein C) increases the risk of myocardial infarction in young women

Factor V Leiden (Resistance to Activated Protein C) Increases the Risk of

Myocardial Infarction in Young Women

By F R. Rosendaal, D S. Siscovick, S.M Schwartz, R K Beverly, B M Psaty, W T Longstreth Jr, T E Raghunathan, T D Koepsell, and P H. Reitsma

Factor V Leiden (factor V Arg506Gln), the genetic defect un-derlying resistance to activated protein C, is the most com-mon risk factor for venous thrombosis The relationship be-tween this genetic abnormality and arterial disease is still unresolved To assess whether factor V Leiden increases the risk of myocardial infarction (MI), we conducted a popula-tion-based case-control study among women 18 to 44 years of age in western Washington state. We included 84 women with first MI and 388 control women, ie, women residing in the same area in the same age ränge without MI (n = 388) The control women were contacted by random digit dialing Data on risk factor Status were collected via personal inter-view, and data on the factor V genotype via polymerase chain reaction techniques The factor V Leiden mutation was

F

ACTOR V LEIDEN is the most common known

heiedi-tary abnoimahty of the clottmg System, with a

pieva-lence of heterozygous carneis of 3% to 5% ' Due to a

muta-tion (Aig506Gln or R506Q) at the cleavage site foi activated

piotem C (APC), clottmg factor V is inactivated at a reduced

rate '

This defect leads to a reduced anticoagulant effect of

APC (APC lesistance), with a less-than-expected

prolonga-tion of the activated partial thromboplastm time (APTT) ^

The reduced anticoagulant effect of the protein C/protem S

natural mhibitoi System leads to an mcieased tendency to

ward thrombosis

Several studies have demonstiated an association

be-tween resistance to activated piotem C and venous

throm-b o s i s

'

Heterozygotes foi the abnoimality aie com

monly found among unselected patients with deep-vem

thiombosis (20%)

and aie even moie frequent among

refeiied patients or patients with farmhal thiombophiha

(40-60%)

Compaied with those wilhout the mutation,

heterozygous cainers of the mutation have a sevenfold

mcieased nsk of venous thiombosis

, homozygous

mdi-viduals have a risk that is increased up to 100-fold

Whethei factoi V Leiden influences the nsk of aitenal

disease is arguable, and few studies have investigated the

association Several reports, mcluding a controlled study

among patients with coionary Stenosis, aie suggestive of an

association with coionary heart disease,

but in seveial

othei contiolled studies no relationship was obseived

The reason foi the lack of consistency among studies is

uncleai but may leflect diffeiences in the pievalence of othei

nsk factois that act syneigislically with factoi V Leiden

When the piesence of anothei factor is impoitant for

mani-festing the elevated risk, this interaction may go unobseived

m studies of selected groups of mdividuals among whom

this other factoi is absent 01 uncommon The conmcting

results also make it unhkely that factoi V Leiden is a majoi

nsk factoi foi aitenal thiombotic disease äs it is of venous

thrombosis Still, even if it had only a modeiate effect on

the nsk of myocaidial mfaiction (MI), 01 if it impaited a

large risk to d subgioup of the population, factoi V Leiden

would be important because of its high allele fiequency and

the large bürden of arterial disease in many populations

found more often in women with MI (10%) than among con-trols (4%). The odds ratio for MI was 2 4 [95% confidence interval (Cl) 1 0 to 5.9]. The risk was increased fourfold (Clgs 1.2 to 12.1) when adjusted for major cardiovascular risk fac-tors. Among nonsmokers the factor V Leiden mutation had little effect (odds ratio 1.1, CI95 0.1 to 8.5), whereas it had a large effect among smokers (odds ratio 3 6, 0195 0 9 to 14 4), which, because smoking was itself a strong risk factor for MI, led to an odds ratio for smoking carriers of the muta-tion that was 32-fold increased compared with nonsmoking noncarriers. We conclude that factor V Leiden increases the risk of MI in young women. This effect seems to be confined largely to current smokers

© 7997 by The American Society of Hematology

We studied the effect of factor V Leiden on the occurrence

of MI among young women in an ongoing population-based

case-contiol study of myocaidial mfaiction and stroke

Be-cause thrombotic factois aie hkely to be most impoitant in

a gioup of young mdividuals among whom atherosclerosis

is less pievalent than it is among older subjects, this study

piovided an excellent opportunity to assess the association

of factoi V Leiden with arterial vascular disease Moieover,

in this population-based study of young patients, other risk

factors, such äs smoking, are highly prevalent, enhancmg

the potential to detect potentially important mteiactions

among risk factors

METHODS

General design We conducted a population-based case control study of MI among women 18 to 44 years of age residing in thiee contiguous counties of westein Washington state The goal was to mclude all quahfymg patients with a fiist myocaidial infarction dur-ing the time fiame of the study Data collection was achieved via peisonal interview, leview of medical recoids and analysis of blood samples This study also mcludes young women with stioke (n = 105, 40 ischemic strokes), among whom we found no excess number

From the Catdwvasculai Health Research Unit the Department of Eptdemiolog) Department of Medicme Depai tment of Health Services and the Division of Newology Umversity of Washington Seattle WA and the Hemostasis and Thiombosis Reseaich Centei and Department of Climcal Epidcmiologv Unneisity Hospital Laden The Nelheilands

Submitted Septembei 16, 1996 accepted Decembei 3 1996 Supported m part by a contiacl from the National Institute for Child Health and Human Development (NO1 HD l 3107) FR R is a recipient ofafellowshipßom the Nedeilandse Oiganisatic voor Wetenschappelijk Ondeizoek (NWO)

Addiess reprmt lequests to F R Rosendaal, MD Department of Climcal Epidemwlogy Bldg l CO-P Univeisity Hospital Leiden PO Box 9600, NL 2300 RC Leiden The Netheilands

The pubhcation costs ofthis artic/e weie defiayed m part by page chaige payment This article must theiefoic be heieby maiked "advertisement" m accoidance with 18 USC section 1734 solely to mdwMte this fact

© 1997 by The Amencan Society of Hematology 0006 4971/97/8908 0017$3 00/0

of caniers öl factor V Leiden and about whom we will not leport furthei heie

Recrmtment of patients Eligible patients weie all 18 to 44-year-old female lesidents of King, Pieice, or Snohomish Counties, Washington, with no pnor histoiy of coionary heart disease or ceie-brovascular disease, who weie diagnosed between July l, 1991, and Februaiy 28, 1995, wilh a first acute MI Cases weie identified thiough the leview of Hospital discharge diagnoses and incident repoits fiom cmergency medical-service Systems Cntena for MI weie adapted from the Caidiovasculai Health Study21 and were de-fmed by evidence of Symptoms, elevated enzymes, and electrocar-diographic changes Usmg these procedmes, we identified 165 eligi-ble patients with MI, of whom 112 could be contacted and were wilhng to participate m an in peison interview

Reciuitment of controls We used landom digit lelephone dialmg to identify a sample of women 18 to 44 years of age hvmg in the same aiea dunng the time penod of the study 26 A household census was completed foi 949% of the lesidences contacted Among the age-ehgible (ιέ, matched to the age distnbution of the cases) women

identified, we landomly chose 691 (one from each household) to be lecruitcd into the study Seven of these women were excluded due to a pnoi histoiy of caidiovasculai disease 01 an mability to speak Enghsh We completed an m-person inleiview with 525 of the re-maimng 684 women for an oveiall response of 72 8% (525/684 X 0949)

Data collection Paiticipating cases and tontrols weie

inter-viewed in person legarding histones of diabetes hypertension, and hyperhpidemia, cigarette smoking, height and weight, reproductive and contraceptive histones, and demographic charactenstics All questions elicited miormation fiom a time penod befoie each wom-an's caidiovasculai event, or an equivalent date foi controls

In addition, we obtamed a 30 mL nonfasting venous blood sample from 84 patients (75%) and 391 (74%) controls who weie mter viewed We compared the women who were inteiviewed and gave blood with those interviewed who dechned venipunctuie and found no impoitant diffeiences Blood was diawn from the antecubital vein in EDTA-treated vacutamers and separated by centnfugation at 2,000g for 10 mmutes, the buffy coat was resuspended m phosphate-buffeied sahne and frozen at -70°C White cell ahquots weie shipped to Leiden, The Netheilands, where DNA analysis was per-foimcd DNA was extracted from these samples äs descnbed by

Millar et al2 7 The presence of the factor V mutation (1,691, G -> A leplacement) was infened fiom the loss of an Mnl I lestnction site äs ongmally descnbed by Bertina et al ' The technicians weie blinded to whether a specimen was fiom a case subject or contiol subject Analyzable DNA was available for 84 women with MI and 388 contiol subjects

Analysis We classificd äs smokers any woman who lepoited smoking cuirently and regulaily, and all otheis äs nonsmokers Women who reported still having menslrual peiiods were classihed äs premenopausal, mcluding women who weie currently piegnant or nursing A woman was classified äs diabetic, hypertensive, 01 hypeicholcsterolemic if she reported that she was currently takmg piescnption drugs foi these conditions, and äs obese when hei body mass mdex (BMI) was equal to 01 exceeded 27 3 kg/m2 These lattei four vanables were giouped together äs metabohc nsk factois

The association of camership of the factor V Leiden mutation with MI was exammed by simple cioss-labulation and by the calcula-tion of the odds ratio äs a measure foi lelative nsk Adjustment loi age was performed usmg unconditional logistic legression, m most instances, unadjusted estimates aie given betause adjustment did not change the estimates The extent to which the associalion belween factoi V Leiden and disease was modified by olhci chaiactenstics was assessed thiough stiatified analyses Conhdence mtervals (CI95)

Table 1 General Charactenstics of Patients and Controls

Age (yr) Mean Range Premenopausal Current smokers Currently treated for

Hypertension Hypercholesterolemia Diabetes mellitus Obese Patients With MI (n - 84) 396 23 44 57 (68) 62 (74) 14 (17) 2 (2) 6 ( 7 ) 51 (62) Controls (n - 388) 3 7 7 19 44 343 (88) 87 (22) 10 (3) 2 (1) 3 (1) 104 (27) Missing are data on BMI in three controls and on hypercholesterol emia m one control Percentages are in parentheses

weie calculated usmg standatd mcthods, le, by Woolf's method 01 from the logistic legiession model

RESULTS

The majonty of the women weie 35 to 44 yeats of age, with a mean age of 38 years (Table 1) Of the 472 women, 72 (15%) had leached menopause (all but foui via hysterec-tomy or bilateial oophorechysterec-tomy), 47 (10%) used oral contra-ceptives Most of the women weie white (89%) Table l furthei shows the distnbution of several major nsk lactors, le, current smoking, pharmacologically tieated hypercholes-terolemia, hypertension, and diabetes mellitus, and obesity (BMI s; 27 3 kg/m2) As expected, these factors weie more common m the patients than m the contiols

Ten percent of the women who had sustamed MI carned the factor V Leiden mutation (8 of 84, 9 5%), compared with 4 1% (16 of 388) of the conlrols (Table 2) The odds latio associated with factor V Leiden foi MI was 2 4 (CI95 l 0 to 5 9) Adjustment for age yielded a similar result (odds ratio 2 4, CI95 l 0 to 5 8) This association changed only m trivial ways when the analysis was lestncted to the white women (OR 2 1), the premenopausal women (OR 2 5), 01 the women not usmg oral conti aceptives (OR 2 5) The odds ratio adjusted for age and major cardiovasculai nsk factors (smoking, diabetes, hypercholesteiolemia, hypeitension and obesity) was 4 0 (CI95 l 2 to 12 1)

Current smoking and the presence of metabohc nsk fac-tors weie strong nsk facfac-tors foi MI Of the patients with MI, 62 (74%) were smokers, compared with 87 (22%) of the controls, smoking was associated with a neaüy tenfold m-creased nsk (OR 9 8, CI95 5 7 to 16 8, age-adjusted OR 8 6, CI95 5 4 to 13 7) One or more of the metabohc nsk factois (hypertension, diabetes mellitus, hypeicholesteiolemia, and obesity) were piesent in 59 (70%) of the patients with MI and 110 (29%) of the control subjects, which mdicates a sixfold mcreased nsk for women with one or moie of these nsk factois äs compaied with women with none of these factois (OR 5 9, CI95 3 5 to 9 9)

FACTOR V LEIDEN AND MI 2819

Table 2 Factor V Leiden Among Patients With MI and Controls Patients With

MI (n = 84)

Controls (n - 388)

Table 4 Factor V Leiden and Metabolie Risk Factors Separate and Combmed Effects on MI

Factor V Leiden (AG) Factor V wild type (GG)

8 ( 9 5 ) 76 (90 5)

16 (4 1) 372 (959)

Valuesarethe number of patients with percentages m parentheses

nsk factors (Tables 3 and 4) The simultaneous presence of

factoi V Leiden and eithei smokmg or one or more ot the

metabolic nsk factoi s led to a 25- to 32-fold mcreased nsk

compared with those without factor V Leiden and smoking

(Table 3) or without factoi V Leiden and one 01 moie

meta-bolic nsk factors (Table 4) When we compared the nsk of

individuals who eithei smoked 01 had one of the metabolic

nsk factors and canied the factoi V Leiden mutant gene

(eight cases, five controls), lelative to those who did not

smoke, had none of the metabolic nsk factoi s, and did not

carry the factoi V Leiden gene (3 cases, 202 contiols), the

odds latio mcieased markedly to 108 (CI95 22 to 532)

The lesults shown in Tables 3 and 4 indicate that factoi

V Leiden cameiship leads to the highest nsk when othei

nsk factois aie also present, although the small number of

mutant gene carners do not allow foimal stalistical tests foi

mteiaction to reach sigmficance The presence of one or

moie of the metabolic nsk factois and factoi V Leiden (Table

4) each mcrease the nsk, which is highest when both aie

piesent, factoi V Leiden cameiship incieases the nsk among

those with one 01 moie metabolic nsk factors (OR 3 9, CI95

0 7 to 22 1) äs well äs among those without one of these

fom metabolic nsk factois (OR 3 6, CI95 l ] to 11 7) For

smoking the lesults aie diffeient the combmed effect of

smoking and factoi V Leiden, which has a high odds latio

of 32, much exceeds the separate effects of these two factois

because smokmg appeais to be a pieiequisite for the

iisk-mcieasing effect of factoi V Leiden, cameiship of factoi V

Leiden increases the nsk among smokeis (OR 3 6, CI95 0 9

to 144) but not among nonsmokeis (OR l l, CI95 0 l to

8 5) In the most extensive model, with adjustment for age

and the piesence of one 01 more melabohc nsk factois, the

nsk was mcreased moie than 50-fold in women who smoked

and camed the mutation äs compaied with nonsmoking

non-carneis (OR 52 5, CI95 11 2 to 247)

DISCUSSION

MI is a i aie event in young women Seveial well-known

nsk factors (hypercholesteiolemia, hypeitension) are also

Table 3 Factor V Leiden and Current Smoking Separate and Combmed Effects on MI Current Smoker No No Yes Yes Factor V Genotype Wild type Leiden Wild type Leiden Patients 21 1 55 7 Controls 288 13 84 3 OR* 1 1 1 9 0 3 2 0 CI95 0 1 8 5 5 1 157 7 7 133 Risk Factors* None None One or more One or more Factor V Genotype Wild type Leiden Wild type Leiden Patients 21 4 55 4 Controls 260 14 108 2 ORt 1 3 5 6 3 2 4 8 CI95 1 1 1 1 7 3 6 109 4 5 194

* All odds ratlos are relative to the reference category, le those who did not smoke and did not carry the mutation Age adjusted logistic regression led to similar odds ratios

* Obesity (BMI =- 27 3) treated hypertension, diabetes, or hypercho lesterolemia, or combmations of same (these data were missmg in four controls)

t All odds are relative to the reference category le those who did not have any of these four nsk factors and did not carry the mutation Age adjusted logistic regression yielded similar odds ratlos

uncommon m the young, which makes this particulai group

well suited to mvestigate new causes of MI This is

espe-cially the case foi thrombotic nsk factois, which may have

a stilking effect m a population in which atheiosclerosis has

had less time to progiess Theiefoie, young women aie an

excellent gioup to mvestigate whethei factoi V Leiden

m-cieases the nsk of MI

Factor V Leiden has been shown to be a stiong and

com-mon nsk factor foi venous thrombosis "

From the

pres-ent study it appears that it is also a deteimmant of myocardial

infaiction m young women, mcieasmg the nsk about

four-fold when othei major risk factois foi MI are taken mto

account

Although we could not mclude women who did not

sui-vive the MI 01 women who refused the interview or the

venipunctuie, it is unhkely that this led to biased results It

is mconceivable that nonresponse would be determmed by

factor V genotype, whereas it is also not hkely that the

women who had died (a much smallei numbei) would have

had an ovei- 01 undei-representation of the mutant gene

The ovei all mciease in the risk foi MI was confined to

women who weie current smokers, and the mteiaction with

smoking appeaied stiong Smoking women who cariied the

factoi V Leiden mutation had a 32-fold mcreased nsk of

MI (50-fold in the most extensive model), wheieas the risk

appeaied not to be mcreased at all m nonsmoking gene

carri-ers These associations are strong but must be mteipieted

with some caution First, the mcidence of MI m young

women is low, theiefore, even a small mcrease m the numbei

of events on an absolute scale leads to laige relative iisks

The findmgs thus aie unhkely to be directly apphcable to

populations with a higher oveiall baselme nsk, such äs oldei

women and men Second, oui estimates aie based on small

numbeis that aie subject to consideiable statistical

uncer-tainty Nevertheless, one may speculate why factoi V Leiden

has a synergistic effect with cigarette smokmg in young

women Both aie eithei fully 01 paitially piothrombotic

fac-tors, wheieas the metabolic factors we mvestigated aie

mamly atheiogenic Since by its chronicity atheioscleiosis

takes more time, it is conceivable that the combmed effect

ot prothrombotic factois Stands out most shaiply m young

individuals

Leiden on coronary artery disease Holm et al reported two women who had MI at the uncommonly young age of 33 and 34 years and who both were homozygous for the factor V mutation 18 In another case senes29 of 60 patients, and

several controlled studies,1421 23 no excess of caniers of

fac-tor V Leiden were found among patients with MI In another large study, however, among 224 patients with angiographi-cally demonstrated coronary artery disease, the factor V mu-tation was found more often m the patients than in 196 controls, with an odds ratio of 2 4 19 In a recent study from

Fmland, the factor V Leiden gene also was found more often

m patients with MI (5 7%) than m controls (2 9%) 20

The discrepancies among studies may well be the result of differences in study populations Most of the previous studies mcluded exclusively or predommantly men The eti-ology of MI may m part diffei between men and women At the biochemical level, it has been demonstrated that estro-gens, endogenous äs well äs exogenous, mciease the resis-tance to APC in women who carry the mutation äs well äs in women who do not In other words, it seems that estrogens further lower the mactivation rate of factor Va by APC 10 It

is therefore possible that factor V Leiden is mamly a nsk factor in women The effect of oral contraceptives m increas-ing the nsk of MI is enhanced by smokmg 24 Previously we

descnbed an interaction between factor V Leiden and the use of oral contraceptives on the nsk of developmg deep-vein thrombosis Ή The small number of oral conti aceptive

users did not allow us to mvestigate this issue here for MI, and additional studies will be needed to clanfy the role and possible interplay of factor V Leiden, smokmg, and esüo-gens in MI

If the effect of factor V Leiden on MI is mamly brought about by an interaction with current smokmg, this findmg also may explam the conflicting results reported so far The Physicians' Health Study14 was conducted äs a nested

case-control analysis among male U S physicians who consented to participate in a randomized tnal of pnmary prevention and who were followed piospectively The number of current smokers among subjects who developed MI was only 16%, which is far lower even than the prevalence m the general population of men m the United States This extremely low prevalence of smokmg may explam why no association be-tween factoi V Leiden and MI was observed m that highly selected cohort, whereas we did find a lelationship m our population-based study of young women among whom smokmg was prevalent (74% of the women with MI)

In conclusion, factor V Leiden is a nsk factor for MI m young women Because of its high prevalence compared with other genetic mutations relevant to thrombosis, the effect of factor V Leiden m populations of other age and sex, m association with other nsk factors, needs to be further deter-mmed

ACKNOWLEDGMENT

We thank the many hospital medical record admmistratois and physicians who assisted m the Identification of patients for this study Fian Chard, Karen Graham, and Carol Handley Dahl expertly ab stracted medical records, and Judy Kaiser, Marlene Bengeult, Carol Ostergard, Denise Hoilandei, and Barb Twaddell recruited and

mtei-viewed the patients and contiol subjects Sandy Tionsdal and Jill Ashman supervised these activiües We thank Esthei Vogels who perfoimed the DNA analyses Fmally, we aie very grateful to all the women who paiticipated m the study

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FACTOR V LEIDEN AND MI 2821

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