milestones in public health: chapter 6

8/14/2019 Milestones in Public Health: Chapter 6

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Chapter 6

Card iovasc ul ar Disease

From rhe lllOlllellt of birth until dealh,the human heart pumps continuously,Normally the size o f a fist, this incred-ibly powe rful muscle literally is lift:itself. The hear t 's form and funC[iOIlhave been stl1died for centu r ies, lea d ingto inc redible advances in knowledgeand interventions. However, cardiovas -cular disease (eV D) rem :lln s the leadingkiller for both men and women among

all racia l an d ethnic groups in rheUnited States. Indeed. cardiovasculardisease was t h e greatest epidemic ofthe 20th ce ntu ry, outstripping lllfcc-t iolls disea ses suc h as polio and AIDS.The epidemic peaked around 1968 inthe United States, with :\11 impressive2.6 perce nt decline in eV D mortalitype r yeJr from 1968 to 1990. TheSedecline s have been recognized as olleof the greatest health achievementS inthe 20th century.

Despite these decline s, Olle person dies every 30 secondsfrom e vo , mo re t han 2,600 people eve ry day . Almost on emillion Americans die o f eV D each year, representing 42percent of :til dCJths. O f these. 160, 00 0 arc indiv iduJlsbetwcen the age s of 35 and 64 years, an indi cation of ho ww idespread eV D is in the popubtion, no t just among ol derAmcri c:tlls. Heart disease and strokt' account for nearly sixIllillton hospitalizations each year and cause disability foralmost 10 million Americans aged 65 ye ars and older. TheCOStS of treJtment approach 5329 billion each year whenlost pr oductivity from disability is factored in, encompass-

ing physic ians,p r o f cs si o n a l ~,

hos piral Jn d nur si ng homeservices, mcdi c:t tions an d home healrh ca re. There is evi-d e nc e that, despite the declines in dCJth rate s, the rate ofne w cases o f e v o ha s no t declined. A larg e proportiono f eV D patients are hving wi th their disease. l3 y 2050, Inestimated 25 million Americans will ca rry the diJgnosi so f coro nar y heart diSCJse.


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Looking Back

A Brief History o f Cardiology

On e o f th e ea rlie st physicians , Imh otep (circa 2725 13 C) ,wa s rC!:,'


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Einthoven received the Nobel Prize for hi s invention in1924, th e same ye :lr th e Allleric:11l Hea r t Asso cia tion wa sfounded. Through the remaining decades of th e 20th ce n -tury , tb e fi eld of ca rdiology became further specialized.Numerous professio nal organizations and associations werec reated to accomtllodate the amazing pace of scien tific andclinical discovery r d ated to th e heart. c


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,Risk faccorsinclude 110n

modifiable risks -age, gender, raceand family history- and behaviorallymodifiable risks,such as obesity,high-f.1t andhigh-cholesterol

dict, a sedentarylifestyle andsmoking.

Case Study

Risk Assessment

Risk f.1ctor screening, accompanied by lifestyle modifications - stich as a healthy diet :md regular exerc ise - calllead [0 early detection of fisk and prevention o f car di ovascular disease. Cardiovascular disc3se l1 SlI:J.lly presents asthree distinct types: coronary artery d i s c : l ~ e(CA D ), strokeand periphera l arterial disease. Atypical presentations alsoabound. .. . Itisk f.1ctors include nonlllodifiable risks -:lgt::, gl'IHier, rac e and f.111lily history - and behaviorallymodifiable risks, such as obesity, high-f.lt :lnd highcholesterol diet, a sedentary lifestyle and smoking. CV D is

also caused by physiologic risk factors, such as hypertension. hyperlipidemia and diabe tes mellitus (types l and 2),which often require pharmacologic treatments in additionto lifesty le modific:ltions.

V:lriOllS tests lIsed to sc reen for CV]) provide a hopefulpath to uncoverlllg and tre:lting C:lrly cardiov:lscubr diseasebefore it develops into a marc serious condition. Physici:lllscan lise simple, noninvasive tests, sLlch as risk-f.1ctor assessments bcfore Illoving to Illore complic:lted - and usuallymore expensive and invasive - tests bter. Risk f.1Ctors forhe:lrt disease to be assessed in pat ients over age 20 include:

Family history of CVD

Smoking status

Dlct. cholesterol ami physical activity

l3lood p ressure

l30dy weight and body mass index

Waist c ircumference

Fasting blood lipid profile

Fasting blood glucoseThese risk factors can be llsed to calculate :l global riskscore ill people 40 years and oldn, providing an es t imateo f th e 10-year risk of heart attaCks and death frolll cardiacd ; ~ e a s e .


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Advances in (he tests currently available fo r hean diseasecontinue to evolve. At present, available noninvasive tes tsinclude:

Resting electrocardiogram (ECG o r EKG)

Signal - averaged electrocardiogram (SAECG)

Chest X-ray

H olter monitor (ambulato ry electrocardiogram)

Echoc ardi ogram

Exercise stress [cst

Co mplU cd tomography (CT) scan

Magnetic reson:l.Ilce imaging (M R I)

Magnetic resonance angiog raphy (MRA)

Nuclear imaging tests, which are noninvasive , include:

MUGA scan

Thallium stress test

Technicium stress test

PE T test

Stress echocardiographyOther invasive imaging tes ts include:

Transesoph ageal echoca rdi ogram (T EE )

Cardiac cathete ri zation ("cath") - also known ascorona ry angiography

Intravascular ultrasound (IVUS)

Recent developments indiC:1te th:lt high levels of tll:1rkerso f infhmmation, su ch :1S C-re:1ctivc pro tein (CRY), Ill:ly:lIsa be markers for incre:lsed ri sk of CVD. As :l sc reening

tool. blood levels of infbmrnatory markers may on e daybecome as familiar as cholesterol an d blood pressurenumb ers, bu t tests with greater specificity need to bedevelope d . In patients presenting with chest pain ofunknown cause, measurement o f c:lrdiac troponin T canreliably detect damage to the heart frOI1l a myo ca rdial

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IIlfarctioll within on e day after the onset o f chest pain, a llindi ca tion o f how co lltinuing improv e mc m s in diagnosti ctests help identif y pati e nt s at high ri sk. Yet another risk fac

tor, fibrinogen , a protein that forms blood elms, is no w alsothought to be a Illark e r for cardiac risk. Finally, a simplemea surement of blood pressur e in the arms and anklesprovide the ankle - bra c hial blood pressure ratio. This hasbee n found to be a reliable predictor o f CVD in peopl eolder than S O years of ag e. IJ

Cbssifica tion 3nd M3!13gc mcm of Blood i'r esmre for Adult s Aged I XY e 3 r ~or Older

HP Systolic Bp Classification I (Illlll!-lg)

Norm.1 tmc,n d


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114

Vignette

Statins

High blood cholesterol is a well-accepted risk factor for CVD.Most ch o lesterol is ca rr i ed in th e blood in two forms, high-densitylipoprotein (HDL ) an d lo w -density lipoprot ei n (LOL), with onlyH D l consid ered advantageous for fighting th e acculllulation o fplaque in th e blood vessels that leads to CVD. A high LDL level , al l

th e other hand , usually signi fi es that a patient is a t risk for eVD.

Federal guidelines on choles terol ha ve changed in the last ten years,with strong er recommendations fo r lowering total c holesterol whilemaintaining appropriate HD L levels. Th e cu rr en t guidelines ar e:

Patients should consume 110 mo r e than seven percent o f calo r ies

from s:tturated fa t (the pr evious recommendation was ten pe r ce nt).

Adults are advised to co n sum e no mo r e than 35 percent ofcalo ri e s from total fat (th e previous recommendation had been30 percent), pr ov ide d that th e main source is unsaturated fats,which do not raise ch o lesterol levels.

Ideal body weight should be attain ed and maintained.

T h e ne w target for dietary choles terol is less than 200 mg pe r day(the pr eviolls target had been under 300 mg per day).

An optimal LDL -C level is 100mg/dL or less pe r day for all adults.

The recommendations ca n be diffi cu lt for th e average healthy consumer [Q follow, and id ea l LDL -choles terollev els may be especi:lllydifficult for so m e CVD patients to achieve through diet alon e. Thedevelopment of the class o f dtugs known as statin s ha s c ha n ge d th eway many physicians manage patients with high ch o lesterol.

Clinical knowledge o f ho w [Q counterac t elevated blood c h olesteroldates back only three decades. Re se:lrc h mt o inhibitors o f H MGCo A reductase, part o f th e body's metabolic pathway fo t th e synt h esisof c hol esterol, began in Tokyo,Japan, in 1971 in th e laboratory ofDr s. Endo and Kuroda. This team reasoned that ce rtain mi c roorga nisms may produce inhibitor s o f this particular enzyme to defendthemselves ag ain st othe r organisms. Th e first agent to be isolated wasm evastatin, a molecule produced by P enicillium citr; IIUIII. Th e pharmaceutical company M e rc k sh ow ed an interest in the research in 1976an d isolated lovastatin from th e mold A spergillus terrel/s. Lo vas tatinwould become the first statin to be cOllllnerci:llly marketed andwould hav e a dramatic effect on the way high choles te rol is treated.


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As of 2005, six statin drugs are on the market in t he United States.Studies using statins have reported 20 percent to 60 percent lowerLDL-cholestcrol levels in patients on these drugs. Statins also reduce

elevated triglyceride levels an d produce a modest increase in HDL-cholesterol. While most patients tolerate statim well, side effectscan include muscle aches and abnormal liver function tests.

Some have questioned th e safe ty of statins, especially g iven theirwidespread use in th e U.S. When a statin is given at a high dose,th e risk for developing abnormalities in liver tests is on e to tw opercent per year. These abnormalities can be reversed, however, bysimply reducing the dose or by stopping t h e drug. Another commonside effect, occurring in somewbere between one to two percent o fpatients, is mus cl e aches or, more rarely, inflammation of th e muscles,called myopathy, in which an enzyme from th e muscle leaks into tbeblood.

Whic h patients are cons idered candidates for statin therapy? The listis lengthy.

Those wh o have had heart attacks or chest pain or those wh ohave undergone bypass surgery or 3ngioplasty, with :an LDL-cholesterol g reater than 100 mg/dL.

T hose with diabetes an d those with multiple other risk factorsfor heart disease with an LDL-c h olesterol greater than 100 mg/dL.

Those with evidence o f blockage in th e arteries carrying bloodto th e b rain (caroti d artery disease) or the legs (peripheral vascular disease).

Those with LOL-cholesterol grea ter than 160 mg/d L and twoother risk factors after :I t he rapeutic lifestyle cha n ge or d lOse

with LOL-cholesterol greater than 190 mg/dL with ei t h er on eor no risk facto rs. As research progresses, however, new lipidtargets may be recognized.

Statin t reat m en t ga ined unintended public attention with the em e rge n cy hear t bypass oper ation of former pres id en t William Cl inton in2004. Some years earlier, an elevated choleste rol count led the fo r me rpresident'S docto r to presc ribe a statin to counte r w hat was fea red tobe incip ien t heart d isease. When th e co u nt returned to safe lev el s relat ively quickly, Preside nt Cl inton chose to d iscontinue usc rather thanfollow medical advice :lnd continue to take th e statin. As t h e worlddiscovered, that choice m ay have been a factOr in the fo r me r presidem's development of coro n ary d isease, unde rscoring t he rule thatonce a patiem b egins a regimen of statins, he sh ou ld continue thatregi m e n fo r t he rest o f his life. D

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Looking Ahead

Obesity in Young Populations

The g rowin g e pid e mi c of obesity in young people offersth e public health co mmunit y a cha lle n ge an d an opportunity to prevent disease an d instill healthy lifestyles. Ho wto prevent obesity is no s ec re t - a c om bin:ltion of physicalactivity and wise choices in nutrition can have an 11llll1ediate impact on weight and foster long-lasting healthy behavior. R ed u ce d weight helps prevent diabetes :md cardiovascular di sease, among other h ealth threats ca used by beingoverweight. Success in thi s endeavor does no t bappenovernig ht an d req ui res :l long-term commitm ent. AnII1vcstment made to d ay by the public health and medicalCOlll tlllllliries, along with sch ool s and governments, willpay dividends in future healthy adult populations.

Th e American H ea r t Association est im ates that the prevalence o f obesity has increased by 75 percent since 1991.M etabolic syndrome, perhaps th e ea rli est wa rnin g s ign o fd eveloping health problems, occurs predominantly in people who are overweight. As many as 55 million Americansm ay m ee t th e diagnostic c rit e r ia for metabolic syndrome.

In [988, Dr. Gerald M. R eavan, an e nd o crinologis t atStanfo rd Un i versity, first described somethmg he calledSyn drom e X, noting th at patie nt s wh o presented with aclus ter of low-level risk f.1.ctors had a substanti all y increasedr isk for heart dise ase. In 1991, th e National CholesterolEducation Program at th e National Institutes o f H ea lthissued a report that renamed Syndrome X as m etabo licsYlld rome. The report em ph asized obesity as a ce lHralcomponen t o f metabo lic syndrome an d recommendedother sc reening tests that would be easy for p r imary caredoctors to use.

P hysicians suspect metabolic syndro m e when people presen t with at least three of the follOWing five criteria: havingan increased girth ar OLind the abdomen, having moderatelyh igh b loo d pr essure, havin g high blood levels of f.1.ts cal!edtriglycerides, ha vi ng low levels of HD L ("good") ch olesterol and having above-average blood sugar. It has beenes timat ed that on e million U.S. teenage rs hav e been di agnosed with th e syndrome, rep rese nt in g fOllr percent o fAmerican ad o lescents . Th ese yo uths ar e believed to be at


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O n e-third toone-ha lf ofth e po p u lat ionwi th metabolicsy n drome subsequently deve lop sd iabetes.

sharply increased risk for developing diabetes when theyarc still in their 20s. if nO t before, an d hean disease as earlyas their 40s.

The American H c;'tr[ Associ:ltion Coullcil on CardiovascularDisease in theVollng recommends early detection o f bloodpressure elevation. Management for prim:lry hypertensionincludes dietary counseling and physical activity prescriptions. Pharm:lCClltic31s :uc reserved only for children whoseblood pressure is consistently very high. Moderation in thelise of salt is also recommended, since the diet of th e aver-age American child contains Illllch morc sodillm than isrequired.

MichJd Weitzman and Steve Cook of th e AmericanAcademy o f Pediatrics' Center for Child Health Rcsearch

and th e De partmellt of Pediatrics at th e University ofRo c h es ter analyzed data on 2,430 adolescents aged 12 t o19 betwee n 1988 and 1994 for th e Na t ional H ealth :l11dNutrit ion Examination Survey, a nat ionally representativeongoing federal survey of th e U.S. population. The studyshowed that 4.2 percellt of a d o l e s c c [ l [ ~ ,or 910,000 teens,met the criteria for metabol ic syndrome. T he syndrome wasfound in at least 6 . 1 percent o f males an d 2 . 1 pe rcent offemales. The researchers found that nearly 30 percent o fthose wh o are cither overweight or obese have the syndrome. Fortunately, if this population loses weight, th e risko f diabetes and heart disease drops sharply .

. . One-third to one-half of the population with metabolic syndrome subsequently develops diabetes. Eve n beforet h e onset o f diabetes, high blood lipids an d other risk fac-tors can ca u st:: cardiovascular disease. The earlier mean ageo f onset for ty p e 2 diabetes o f adolescents is startling anddistur b ing, because CV D development that takes place overm:l1ly yea rs in adults starts much earlier, potentially leadingt o onset of CVD in early and mid adulthood. Oel1lg overweight is ne:arly :alw:a ys the trigger for type 2 diabetes (ve r-sus type 1 diabetes, which is triggered by abnormalities ininsulin produc t ion and usually diagnosed in childhood).

The onset o f di :a bctcs carries with it th e distressing probability of cardiovascular dise:ase within twO deca d es, greatlyinc reasing the chances for premature de:ath. l3Iac k andHispanic Americ:ans have nearly twice tbe inc idence oftype 2 diabetes :as whites and many Native Americ:an tribesare experiencing epidemic rates.


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... Th e !lumber of overweight children tripled between1970 an d 2000, reaching 15 pcrcellt of those between theages of six and 19. The highest growth rates have been in

African-American and Hispanic youth wh o live mainlyin inn er cities, where access to opportunities for physicalact ivity is often limited. In addition, research has shownthat adolescents wh o exhibit hi gh levels o f hostility aremore prone to becoming obese an d developing insulinresistance, cwo markers o f metabolic sy ndrom e that makethese youth more likely to develop cardiovascular diseasein adulthood. Current research also links sleep disorderswith metabolic syndrome.

To counter these disturbing trends, th e public health community is seeking new ways to communicate th e benefitsof weight control, hcaithier eating and ph ysical activi ty toreinforce even more effectively that improved lifestyle is akey to good health for young adu lts and children. Trail1lngchildren to live healthy lifestyles can improve cardi o vascularhealth in adu lt life and is a strat egy that must becomewidespread in schools, especially inner-city schools thatse rve a high proportion o f minority populations.

The health benefi ts associated with a physically activelifestyle in child ren include weight control, lower bloodpressure. improved psychological well-being and a predis-position to increased physical activity in adulthood.Inc reased phys ical activity has been associated with an

increased life ex pectancy an d dec reased risk of ca rdiovascu-lar disease. R esearchers have also shown that people wh ocat breakfast every day, espec ially whole-grain ce real, aref:1r less likely to be obese or have diabetes or heart disease.

A healthy level of phys ical activity requires regular participation ill activities that generate ene rgy expendi tur es sig-nificantly above th e resting level and ideal ly grea ter thanhalf of maximum exe rtion . These activities may be accomplished through both recrea tional pastimes and organizedSpOrt s. Physical activity in American childre n, however, hasdiminished for a variety of reaso ns. Children rely more on

the automobile fo r transportati on , as opposed to walkingor bicycling. Growing numbers of chi ldren also e n gage insede ntary e m ertainment, including tel ev ision, video gamesand co m pu t e rs. Unfortunately, pa r ticipat ion in organizedathletics diminishes greatly afte r middle sch oo l , a spec ialproblem for girls.

,

The numb ero f overweightchi ld r e n tripledbetw ee n 1970 and2000, reaching 15p erce nt of thosebe twee n th e agesof six and 19.


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In large c iti es,a lack of safeoutdoor play areaslimit s ch i ld r e n 'sabi lity to participate in activ ephysical play orrecreationalSpOrts.

Although these trends of diminished physical activityare nationwide, socioeco llo mi c factors place certain subpopulation s of children at greater risk. . . [n large cities,

a lack o f safe outdoor play areas limits children's abilityto participate in active phy sical play or recr eational sports.With tightening sc hool budgets and changes in curricldlllll,regubr physic;'!] ed u cation in sc hools ha s been d e-emphasize d.Th e number of families with two working parents or asingle parent bas increased, with th e result chat 111:I11Y moreparents are limited in theif ability to encourage participation.

Federal, state and lo ca l h ea lth departments are workingtogether [Q counter th e se alarming trends. CDC. aftermuch analysis an d collaborat io n , published the followinghealth promotion and disease-prevention strategies aimedat obesity:

Ensure daily quality phys ical education for all schoolgrades.

Ensure that more food options that arc low in f:1 t :lT1dcalories, as we ll as fruits, vege tabl es, whole grains andlow -fat or nonfat dairy products, arc available onsc h ool campuses and at school events.

Make cOll1ll1llllity r.1cilities available for ph ysicalactivity for all people, including on weekends.

Create more opportunities for physical activity atwork sites.

Reduce tim e spent watching television and in o th ersedentary behaviors. In 1999,43 percent of highschoo l sw dents reported watching tw o hours of TV

or 1110re a day.

Educate all expectant paTems about th e benefits o fbreast - feeding. $mdies indicate that breast-fed infam smay be less likely to be com e overweight as t h ey growolder.

Change th e pe rce ption of obesity so that healthbecomes th e chief co ncern, no t personal appearance.

In crease res ea rch on th e behavioral and biologicalcaus es of overweight and obesi ty. Direct researchtoward prevention and tr eatment and towardethnic/racial health disparities.


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Edu cate health ca re providers and health professionstu d ents on the prevention and treatmenr o f over-weight and obesity across the lifespan.

Although it is widely accepted that healthy diets and dailyphysical activity together help control we ight and preventth e onset of CVO, the American population n o n e t h c 1 e ~ s

suffers from an epidemIc of overweight and obesity.Currently 122 million adults are overwt:ight and at risk forhypertension and related condit ions that ca n lead to CVO.

The well - kn ow n benefits of physical activity and a healthydiet have no t forestalled the epi d emic of overweight andobesity in the United St3tes no r th e resulting epidemicof diabetes and cardiovascular di sease. Unless significantchanges arc made, today' s overweight and obes e children

will be tomorrow's unhealthy adults. No t only will thisaffec t the health of th e U.S. population, it will also becomean economic drain on an alre ad y overburdened health caresyStem. All of the diagnostic and treatment advances inCV O should mean that this disease i s ab3 tin g. Unfortunately ,th e incidence ofCVO is no t declining , 3nd th e public healthcommunity ~ in partnership with medical, educational an dlegislative en titi es - mUSt find innovative solutions to thischallenge.

Thomas A. Pearson, MD, MP H , Ph D , Pr ofessor ofCommunity and Preventiv e M edicine at rhe Universityof R.. ochester, suggests, . . "The spectacular reductionsin cardiovascular d isease mortality see n in the 19705 and19805 are in great danger due to th e obesity epidemic. Forth e first time in U.S. history, experts are warning that th elife expectancy of ou r childre n may be les s than ou r own.These dire pr edic tion s ari se from the epidemic of obesityin ou r c h ildren and th e return o f the eVD epidemic 3Sthe y be com e adults. A combi n ed effort o f cl ini cal alldp ubl ic health strategies to reduce obesity will be absol ut e-ly essent ial. If we t:1il, th e 2010 health goals set for th eUnite d State s will prove unattainable." a

Dr. TJ,omas A .Pcar so ll , proJc5Sor (ifCo m,mll/ilyand

Pr evwlillC M ed i( i,, /,ar lirl' UuivwilyoJRo circsler.

,"T h e sp ectacularreduct ion s inca rdiovas culard isease mortalityseen in the 19705and 1980s arein great dangerdue to th e obesityepidemic."


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milestones in public health: chapter 6

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