jwa 14 (1-2) journal pnline.vp

24 Pages·2007·0.2 MB·English

Gender Differences in Disability-Free
Life Expectancy for Selected Risk Factors
and Chronic Conditions in Canada
AlainBélanger,PhD
LaurentMartel,MSc
Jean-MarieBerthelot,BSc
RussellWilkins,MUrb
SUMMARY.Thisarticleshowshowmortalityandmorbiditypatternsdif-
ferforwomenandmen45yearsofageandolder.Theimpactondisabil-
ity-freelifeexpectancywascalculatedforselectedriskfactorsandchronic
conditions:lowincome,loweducation,abnormalbodymassindex,lackof
physicalactivity,smoking,cancer,diabetes,andarthritis.Foreachfactor,
theexpectednumberofyearsfreeofdisabilitywascalculatedformenand
womenusingmulti-statelifetables.Intermsofdisability-freelifeexpec-
tancy, the greatest impacts on affected women were for diabetes (14.1
years), arthritis (8.8 years), and physical inactivity (6.0 years), while for
affectedmen,thegreatestimpactswerefordiabetes(10.5years),smoking
Alain Bélanger and Laurent Martel are affiliated with the Demography Division,
while Jean-Marie Berthelot and Russell Wilkins are with the Health Analysis and
ModelingGroup,StatisticsCanada,Ottawa,ON,Canada,K1A0T6.
Addresscorrespondenceto:AlainBélanger,DemographyDivision,StatisticsCanada,
Ottawa,ON,CanadaK1A0T6(E-mail:[email protected]).
TheviewsandopinionsexpressedinthispaperdonotnecessarilyreflectthoseofSta-
tisticsCanada.
TheauthorsaregratefultoHealthCanadaforfunding,andtoKathyWhiteforeditorial
assistance.
[Haworthco-indexingentrynote]:“GenderDifferencesinDisability-FreeLifeExpectancyforSelectedRisk
FactorsandChronicConditionsinCanada.”Bélangeretal.Co-publishedsimultaneouslyinJournalofWomen&
Aging(TheHaworthPress,Inc.)Vol.14,No.1/2,2002,pp.61-83;and:HealthExpectationsforOlderWomen:
InternationalPerspectives(ed:SarahB.Laditka)TheHaworthPress,Inc.,2002,pp.61-83.Singleormultiple
copiesofthisarticleareavailableforafeefromTheHaworthDocumentDeliveryService[1-800-HAWORTH
9:00a.m.-5:00p.m.(EST).E-mailaddress:[email protected]].
2002byTheHaworthPress,Inc.Allrightsreserved. 61
62 HEALTHEXPECTATIONSFOROLDERWOMEN:INTERNATIONALPERSPECTIVES
(6.9years),arthritis(6.5years),andcancer(6.4years).Theimplicationsof
these results are discussed from the perspective of developing programs
designedtoimprovepopulationhealthstatus.[Articlecopiesavailablefora
fee from The Haworth Document Delivery Service: 1-800-HAWORTH. E-mail
address: <getinfo@haworthpressinc. com> Website:
<http://www.HaworthPress.com>©2002byTheHaworthPress,Inc.Allrights
reserved.]
KEYWORDS. Mortality, morbidity, disability-free life expectancy, risk
factors,genderdifferences
INTRODUCTION
In Canada, as in many other developed nations, gender differences in
health present somewhat of a paradox. On the one hand, life expectancy
for Canadian women has been greater than for Canadian men for over a
century–81.4 and 75.8 years, respectively, in 1997 (Statistics Canada,
2001a).Ontheother,Canadianwomenreportedmorechronicconditions,
andtheyusedhealthcareservicesmorefrequently,particularlyatages65
andover(StatisticsCanada,2001b).Theyalsohadhigherratesofdisabil-
ity (Statistics Canada, 2000). Thus, while women certainly live longer
thanmen,theirhealthisnotasgood.
Life expectancy is often used alone as an aggregate indicator for de-
scribingthehealthofapopulationoritscomponentgroups,basedonthe
assumption that expansion of life expectancy implies better health.1 It is
tempting to consider the health of men, with a life expectancy 5.6 years
less than that of women, to be the greater concern and thus the focus of
moreattentionbypublicdecisionmakersinvolvedindefininghealthpoli-
cies. Mortality and morbidity are, however, two distinct measures that
may,infact,providequiteoppositeperspectives.
Inanagingsocietyinwhichthemajorityofseniorsarewomen,whore-
portmoredisablingchronicconditions(Manton,1997),weneedotherag-
gregateindicatorsofhealththatprovideinformationonbothmortalityand
morbidity.Onesuchindicator,disability-freelifeexpectancy,canbeused
toqualifyyearsoflifeaccordingtowhethertheyarewithorwithoutdis-
ability.Insodoing,thisaggregatehealthindicatorshedsmoremeaningon
longerlifebyhelpingtodeterminewhetheranincreaseinaveragelifespan
isaccompaniedbybetterqualityoflife.Oncethisindicatorhasbeenesti-
matedforbothsexes,itcandemonstratehowtheagingofmenandwomen
Bélangeretal. 63
differsintermsoffunctionalhealth.Intheshortterm,asacceleratedaging
of the Canadian population threatens to trigger a significant rise in costs
for health care and related services, living not just longer, but in better
healthandwhilemaintainingphysicalautonomy,wouldappeartobeade-
sirablegoal.Strategiesaimedatcompressionofmorbidity,whichmaybe
differentforeachsex,thuswarrantspecialattention.
This research assesses the effects of various risk factors and chronic
conditions on disability-free life expectancy for Canadian men and
women. In a prior study, numerous factors were significantly associated
withthelossandrecoveryoffunctionalautonomy(Martel,Bélanger,and
Berthelot,2000).Thecurrentstudycomparestheeffectofseveralofthese
factors (education and income as social factors; physical activity, body
mass index, and smoking as behavioural factors; arthritis, diabetes, and
cancer as chronic conditions) on the life expectancy and disability-free
life expectancy of Canadian men and women. To our knowledge, there
hasbeennootherstudyonthissubjectforCanada.
Becausefunctionalhealthisadynamicprocess,i.e.,apersonwhohas
lost physical autonomy could subsequently recover it, the method used
here to calculate disability-free life expectancy is based on multi-state
life tables. More complex than the well-known “Sullivan” preva-
lence-based method, this method considers the flow into and out of dis-
ability,referredtoas“transitionsbetweenfunctionalstates.”Thismethod
also allows for explicit differences in mortality between different func-
tional health states. A longitudinal survey is necessary to calculate these
transitionsandinthiscasetheCanadianNationalPopulationHealthSur-
vey(NPHS)wasused.TheNPHSisthefirstlongitudinalsurveydesigned
toenhanceunderstandingoftheprocessesaffectingthehealthoftheCa-
nadian population as a whole, including persons living in private house-
holdsandhealth-relatedinstitutions.
BACKGROUND
To our knowledge, few studies have estimated the impact of various
health risk factors and chronic conditions on disability-free life expec-
tancy, particularly by using the multi-state method. Various work has,
however,beenconductedtoexaminetheeffectondisability-freelifeex-
pectancyofsmoking(Rogersetal.,1994;Nusselder,1998;Ferruccietal.,
1999), physical activity (Ferrucci et al., 1999), certain chronic illnesses
(Nusselder,1998),maritalstatus(Naultetal.,1996),andsocioeconomic
status(Guralniketal.,1993;LeighandFries,1994;Wigle,1995;Naultet
64 HEALTHEXPECTATIONSFOROLDERWOMEN:INTERNATIONALPERSPECTIVES
al.,1996;Valkonenetal.,1997;DoblhammerandKytir,1998;Melzeret
al.,2000).
Many studies have highlighted the links between socio-economic sta-
tusandhealth.Thehighertheeducationalorincomelevel,thegreaterlife
expectancyandbetterhealth.Melzeretal.(2000)showedthatahighered-
ucational level was associated with a relative compression of morbidity,
asmembersofhighersocialclassesnotonlyenjoyedlongerlifeexpectan-
cies,butalsoagreaterproportionofsuchyearslivedingoodhealth.Simi-
larresultswerealsoreportedbyLeighandFries(1994)andDoblhammer
andKytir(1998).Valkonenetal.(1997),however,reportedthatthenum-
ber of years lived with disability remained higher among women than
among men whatever the educational level, both because of their longer
lifeexpectanciesandtheirlikelihoodofdisability.
According to Nault et al. (1996), differences between Canadian men
and women with respect to mortality and morbidity diminished with in-
creasingsocioeconomicstatus.InanotherstudyoftheCanadianpopula-
tion,Wigle(1995)showedthatdisability-freelifeexpectancyinCanada
was much lower for individuals falling into the bottom income quintile
compared with those in the top (a difference of 10.1 years for men and
11.3 years for women). Differences in mortality and morbidity by
socioeconomicstatusthuspersistinCanada,despitetheprinciplesofuni-
versalcoverageandaccessibilitythatunderpinCanada’shealthcaresys-
tem.
Withrespecttobehavioursaffectingmortalityandhealth,allstudieson
smokinghavedemonstratedtheextenttowhichitcontributestomortality
and morbidity. Ferrucci et al. (1999), Nusselder (1998), and
Bronnum-HansenandJuel(2001)showedclearlythatalowerprevalence
ofsmokingresultednotonlyinlongerlifeexpectancyanddisability-free
lifeexpectancy,butalsoreducedtheproportionoflifelivedwithdisabil-
ity. In other words, smoking reduction led to a relative compression of
morbidity.Ferruccietal.(1999)showedthatregularphysicalactivityalso
yieldedthesameresult.
Fewstudieshaveassessedtheimpactofchronicillnessesonbothmor-
talityandmorbidity.Usinganapproachdifferentthantheoneemployed
inourresearch,Mathers(1992)andNusselder(1998)illustratedtheeffect
ofeliminatingagivenillnessonlifeexpectancyandondisability-freelife
expectancy.2 She concluded that eliminating non-fatal chronic illnesses,
suchasarthritisandbackpain,wouldleadtoasubstantialriseindisabil-
ity-free life expectancy, without significantly increasing life expectancy.
Thismeansthateffortstoeliminatethesediseasescouldproduceanabso-
lutecompressionofmorbidity.Ontheotherhand,theeliminationofmore
Bélangeretal. 65
fataldiseaseslikecancerorheartdiseasecouldleadtoanexpansionofmor-
bidity, as their impact on life expectancy alone was much greater than on
disability-freelifeexpectancy.
More recently, Laditka and Laditka (2001) have shown that inividuals
sufferingfromdiabetescanexpecttolivefeweryearsofbothtotalandun-
impaired life, indicating that this chronic disease has a major impact on
healthexpectancy.
Thecalculationofindicatorssuchasdisability-freelifeexpectancyor
healthy life expectancy requires access to detailed health surveys and is
not yet very widespread, particularly using the multi-state life table
method. Simultaneously comparing the impact of multiple risk factors
and chronic conditions on disability-free life expectancy computed
through this method is thus a first in largely uncharted territory. This
meanswewillnotbeabletodirectlycompareourresultsherewiththose
presentedinoursurveyoftheliterature.
DATAANDMETHODS
TheNationalPopulationHealthSurvey(NPHS)waslaunchedbySta-
tistics Canada in 1994. It provides both cross-sectional and longitudinal
data on the population living in private households and those living in
health-relatedinstitutions.Itslongitudinaldimensioninvolvesinterview-
ing respondents every two years to gather detailed information on their
physicalandmentalhealth,activitylimitationsanddisabilities,useofand
accesstohealthcare,chronichealthproblems,lifestyle,andhealth-related
behaviours.
The NPHS longitudinal sample included 17,276 respondents living in
privatehouseholdsand2,192livinginhealth-relatedinstitutionsin1994.
Asourstudywasrestrictedtoindividuals45yearsofageorolder,36,053
respondentsinprivatehouseholdsand1,956ininstitutionswereselected
fromtheinitialsample.OnlythefirsttwoNPHScycles(1994and1996)
wereused.Losstofollow-upbetween1994and1996wasverylow,and
didnotconstituteamajorsourceofbias.4
FunctionalHealthStates
Healthasaconceptisdifficulttodefinebecauseitinvolvesmorethan
justtheabsenceofdisease.Bydefininghealthasafunctionalstatethatei-
therdoesordoesnotpermitautonomyinactivitiesofdailyliving,wecan
66 HEALTHEXPECTATIONSFOROLDERWOMEN:INTERNATIONALPERSPECTIVES
thenlinkhealthstatustoitspotentialburdenontheformaland/orinformal
supportnetwork.
Operationally,twoconceptswereusedandcombinedunderthege-
neric term “disability” in order to define an individual’s functional
state:activitylimitationsanddependency.Inthefirststate,respon-
dentswereconsideredtobe“disability-free”iftheyreportednoactivity
limitationsandnodependency.Thesecondstateof“slightormoderate
disability”includedrespondentswhohadsomeactivitylimitationsbut
no dependency, or who needed assistance from someone for heavy
householdchores,shoppingornormaleverydayhousework,whetheror
nottheyreportedanyactivitylimitations.Indi-vidualswith“severedis-
abilities”arethosewhorequiredassistancefromanotherpersoninpre-
paring their meals, in providing their personal care, or in helping them
getaboutthehouse,whetherornottheyalsohadanyactivitylimitations.
Finally, residents of long-term health-related facilities constituted the
fourthfunctionalstate:“institutionalization.”
Ahigherproportionofwomenthanmen45yearsorolderwereclassi-
fied as disabled (Table 1), suggesting poorer functional health among
thefemalepopulation.Womenreportedmoredisablingchronicdiseases
thanmenandwerealsoolderonaverage(StatisticsCanada,2000).Rela-
tivelyfewmenreportedthattheyneededoutsidehelpinpreparingtheir
meals,shopping,orfornormaleverydayhousework,suggestingthatde-
pendencyinthesetasksmayberelatedtothegenderdivisionofhousehold
work,atleastforthegenerationsunderstudy.Theuseof“activitylimita-
tions,”whichislesssensitivetotraditionalgenderroles,allowedustore-
TABLE1.DefinitionsoftheFourFunctionalStatesandTheirPrevalenceinthe
CanadianPopulationAged45andOver,bySex,1995
FunctionalState ActivityLimitations Dependency Prevalence(%)
Men Women Total
Disability-free None None 72.8 66.9 69.7
Slightormoderatedisability Yes No
Yesorno Heavyhouseholdchores, 20.8 24.5 22.7
shoppingforgroceries,
normaleveryday
housework
Severedisability Yesorno Mealspreparation, 5.1 5.9 5.5
personalcare,moving
aroundthehouse
Institutionalization -- Residenceinalong-term 1.3 2.8 2.0
health-relatedfacility
Bélangeretal. 67
duce its impact on observed prevalence, thus making it easier to create
relatively homogeneous functional states that included enough cases to
yieldreliableestimates.
RiskFactors
Table 2 defines the risk factors and chronic conditions examined and
theirprevalencewithinthestudypopulation.Respondents’educationwas
categorized as “high school graduation or less” or as “at least some
post-secondary.”Theproportionofwomenwithalowereducationallevel
was only slightly higher than that of men, which was to be expected
amongthegenerationsunderstudy.
The income variable divided the population into two groups with
cut-offs which varied according to the number of people living in the
household:“lowincome”and“middleorhighincome”weredefinedasin
Table 2. Almost one in four women lived in a low income household,
whilethiswasonlytrueofaboutoneinsevenmen.Onceagain,thesere-
sultshavebeenaffectedbythegenerationalfactor,asmanyolderwomen
did not join the workforce during what would have been their working
lives. Given the relationship between health and socioeconomic status,
women, who tended to have less education and lower income than men,
wereatadisadvantagewhenitcomestoriskfactorsforhealth.
Inthisstudy,arespondentwhoreportedbeingadailysmoker,anocca-
sional but formerly daily smoker or a former smoker who had stopped
withinthepriorfiveyears,wasclassifiedasasmoker,sincethereisala-
tencyperiodformanysmoking-relateddiseases.Conversely,respondents
who had never smoked, who had stopped smoking more than five years
earlier or who were always only occasional smokers were classified as
non-smokers.Aboutoneinthreemenaged45orolderfellintothesmoker
category. Among women the proportion was only one in four. Note also
thatrelativelyfewwomennowintheolderagegroupssmokedbeforethe
1970s.
Body mass index (BMI) was obtained by dividing an individual’s
weightinkilogramsbythesquareofhisorherheightinmetres.Various
standards define underweight and obesity, the most common being the
WorldHealthOrganizationdefinitionofunderweightasaBMIof#18.5
andobeseas$30.0(WHO,1995).Wechoseadifferentapproachhere,
whichbeganbyclassifyingthepopulationintodecilesofBMIbyageand
sex.Individualsfallingintotheextremelowerorupperdeciles(thefirstor
tenth)wereconsideredtobeof“abnormal”weight.5Thismethodresulted
68 HEALTHEXPECTATIONSFOROLDERWOMEN:INTERNATIONALPERSPECTIVES
TABLE2.DefinitionsoftheVariousRiskFactorsandChronicConditionsand
TheirPrevalenceintheCanadianPopulationAged45andOver,bySex,1995
Riskfactoror chronic Definition Prevalence(%)
condition
Men Women Total
Education
Lowereducation Highschoolgraduationorless 51.3 55.3 53.4
Highereducation Atleastsomepost-secondaryeducation 48.7 44.7 46.6
Income*
Lowincome Lessthan$15,000foraoneortwopersonhousehold 14.4 23.6 19.3
Lessthan$20,000forathreeorfourpersonhousehold
Lessthan$30,000forafiveormorepersonhousehold
Middleorhighincome Atleast$15,000foraoneortwopersonhousehold 85.6 76.4 80.7
Atleast$20,000forathreeorfourpersonhousehold
Atleast$30,000forafiveormorepersonhousehold
Smoking
Smoker Dailysmoker 31.8 23.9 27.6
Occasionalsmokerbutformerdailysmoker
Formersmokerwhostoppedlessthan5yearsago
Non-smoker Alwaysanoccasionalsmoker 68.2 76.1 72.4
Formersmokerwhostoppedmorethan5yearsago
Neverasmoker
BodyMassIndex
AbnormalBMI Deciles1and10foragegroupandsex 20.0 20.0 20.0
NormalBMI Deciles2to9foragegroupandsex 80.0 80.0 80.0
PhysicalActivity**
Inactive Lessthan1.5kcal/kg/dayofenergyexpenditure 61.9 67.2 64.8
Active 1.5kcal/kg/dayormoreofenergyexpenditure 38.1 32.8 35.2
Arthritis
Yes Arthritiseverdiagnosedbyahealthprofessional 21.1 33.3 27.7
No Neverdiagnosedwitharthritis 78.9 66.7 72.3
Diabetes
Yes Diabeteseverdiagnosedbyahealthprofessional 7.3 6.2 6.7
No Neverdiagnosedwithdiabetes 92.7 93.8 93.3
Cancer
Yes Cancereverdiagnosedbyahealthprofessional 2.8 4.3 3.6
No Neverdiagnosedwithcancer 97.2 95.7 96.4
*Householdincomeforpersonslivinginprivatehouseholds;personalincomeforpersonsresidinginhealth-related
institutions.
**Leisuretimephysicalactivity.
in no difference in prevalence by sex, since by definition, 20% of both
menandwomenwouldbeofabnormalweight.
The NPHS was used to calculate total cumulative energy expenditure
ofrespondentsduringtheirleisureactivitiesbasedontheirweightanddu-
ration of leisure activities during the three months preceding the inter-
view. Active individuals were those who expended more than 1.5
Bélangeretal. 69
kilocalories per kilogram of body mass per day, which corresponds to
moderateorintensephysicalactivity.Inoursample,somewhatmoremen
than women were physically active according to this definition, which
also corresponds to results generally appearing in reports on men’s and
women’shealth(StatisticsCanada,2000).
Finally, concerning chronic conditions, respondents were asked if a
healthcareprofessionalhadeverdiagnosedthemwithoneofalistofvari-
ous health-related problems.6 Based on these questions, the respondent
wascategorizedaseverorneverdiagnosedwitharthritis,diabetes,orcan-
cer.Thesurveyquestionnairedidnotprovideanyadditionalinformation
onthetypeorseverityofthedisease(suchaswhetherdiabeteswastypeI
ortypeII).
Theprevalenceofdiabetesandcancerwassimilaramongbothsexesin
thepopulationaged45andolder.Arthritis,however,presentedfairlydif-
ferentprofilesforeachsex,withfarmorewomen(oneinthree)thanmen
(oneinfive)reportingthattheyhadbeendiagnosedwiththischroniccon-
dition.
Methods
Thecalculationofdisability-freelifeexpectancyusingmulti-statelife
tablesisbasedonestimatingtwoelements:thefirstisthemortalitydiffer-
entialbyfunctionalstateandriskfactororchronicconditionandthesec-
ond is the transitions between the different functional states for the
populationswithandwithouttheriskfactororchroniccondition.
SincetheNPHSsamplewasrelativelysmall,estimatingmortalityrates
byage,sex,andthefourfunctionalstatesdidnotproduceveryrobustre-
sults using only the survey data. However, life tables produced from the
vital statistics provided a better estimate of mortality for the Canadian
populationasawhole.Themethodusedtoestimatethemortalitydifferen-
tial by functional state took advantage of this information and used the
surveydatatoincreaseordecreasetheriskofdeathofindividualsaccord-
ingtotheirfunctionalstatereportedinthefirstcyclebymeansofanesti-
mation of relative risks. Obtained by using a proportional hazard model
(Coxregression),7theserelativerisksforeachofthestateswereappliedto
theprobabilityofdyingfromtheCanadianlifetables(basedonvitalsta-
tistics)toproducenewprobabilitiesofdyingforeachfunctionalstate.The
mortalitybaselevelwas,therefore,areliableestimatethattookthewhole
of the Canadian population into consideration. For each risk factor or
chronic condition, the respective prevalences were used in combination
with these new probabilities of dying to generate a new life table for the
70 HEALTHEXPECTATIONSFOROLDERWOMEN:INTERNATIONALPERSPECTIVES
total population which showed approximately the same life expectancy
obtainedusingthereferenceCanadianlifetablesbasedonvitalstatistics.
Becauseofthesmallsamplesize,thedirectcalculationoftheprobabil-
ityofmakingatransitionbetweeneachfunctionalstate–byage,sex,and
risk factor or chronic condition–would introduce undesirable random
variations from one age group to another. Instead, transitions between
functionalstatesbyageandsexforeachriskfactorandchroniccondition
were estimated using a generalized logit model8 which eliminated those
random variations. For each original functional state, the probability of
making a transition to another state was assumed to be a function of age
andsex,theonlytwovariablesincludedintheregression.Themodelpro-
videdforinclusionofcompetingrisks,thatis,thattheprobabilityofmak-
ingatransitionfromonefunctionalstatetoanotheralsodependedonall
oftheotherstates.Thesetransitionsweremodelledforeachofthevarious
riskfactorsandchronicconditioncategories.Weassumedthatindividu-
alswhodiedbetween1994and1996livedhalfthattime(oneyear).Re-
sultsarepresentedfor1995,halfwaythroughtheintervalbetweenthefirst
twoNPHScycles.
Tosimplifythereportingofresults,“disabledlifeexpectancy”(DLEor
DLEAnyinthetables)includesmoderatedisability,severedisability,
and institutionalization, while “severely disabled life expectancy”
(DLE Severe in the tables) includes severe disability and
institutionalization.
RESULTS
Table 3 presents life expectancy and disability-free life expectancy in
years,bysex,foreachriskfactorandchronicconditionstudied.Theyears
livedwithseveredisabilityorinahealth-relatedinstitutionarealsopro-
vided.Totallifeexpectancyatage45,asestimatedbythemulti-statelife
tablemethod,was32.9yearsformenand37.7yearsforwomenin1995
(Table3).Bycomparison,lifeexpectancyatthesameageaccordingtothe
officialStatisticsCanadalifetablesbasedonvitalstatisticswas32.7years
formenand37.6yearsforwomen(Bélanger,1999).Theestimateoflife
expectancy based on the method used here thus seems to be fairly accu-
rate, given the random variation due to use of data from a sample-based
survey.
Of the two socio-economic factors appearing in Table 3, differences
betweenlowandhigheducationallevelsproducedthelargereffectswith
respect to mortality: nearly 6 years of life expectancy for both men and