Using Spatial Epidemiology as a Tool to Better Understand Influenza-like Illnesses by Andrea ... PDF
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UsingSpatialEpidemiologyas aTooltoBetterUnderstand Influenza-likeIllnesses by AndreaRush-Sirski DepartmentofCommunityHealthSciences UniversityofManitoba AThesissubmittedtotheFacultyofGraduateStudiesof TheUniversityofManitoba inpartialfulfilmentoftherequirementsofthedegreeof MASTER OFSCIENCE Copyright©2013byAndreaRush-Sirski Abstract InfluenzaisapopulationhealthissueinCanada,withanannualinfectionrateof 10-25%ofthepopulation. Thepurposeofthisthesis wastoanalyzeinfluenza-like illnesses(ILI)forthefiscalyears(April1toMarch31)from 2004-05throughto2008- 09,bothspatiallyandtemporally,throughouttheprovinceofManitoba. ILI, forthe purposeofthis study,includeddiagnosesofpneumoniaandinfluenzaand acute respiratoryinfectionasdeterminedbyICD-09 andICA-10codes. As withother publishedstudiesandtheaccepteddefinitionsof ILI, repeatcaseswithinaseasonwere included.Theanalysisusedaframeworkspecifictospatialanalysis,andincorporatedthe principlesofpopulationhealthandecologicalframeworks. Theunderlyingobjectivesof theresearchweretobetterunderstandthepatterns of ILIdiagnoses aswell as the characteristicsofthosediagnosed. Thedatawereexploredinthreeways: employingmethodsofdatavisualisation, explorationandmodeling,withtheincorporation ofthedeterminants ofhealthtoinform theresultsand guidethechoiceofregressionvariables. Differentmapswerecreatedto showtheresultsfromvarious perspectivesandnegativebinomialregressionanalysis was usedtotestwhich,ifany,ofthechosenvariables (includinghouseholddensity, co- morbidityscore,incomequintileandage)weresignificant. Basedonthisresearch,onecouldconcludethatalthoughclustersofILIdo exist intheprovinceofManitoba,aclearrelationshipdoesnotexistbetweenthedeterminants ofhealthand ILIas was expected. Althoughthe agevariable yieldedpredictableresults, higher riskofdiagnoses amongstthehighdensityhouseholds orinthelowestincome ii quintileswasnotobserved. Itishoweverunclear as tohowtheseresultswereaffectedby thelimitationsofthestudy, particularlytheinclusionofrepeatcases. iii Acknowledgements Although Iamtheauthorofthisthesis,Ifeelconfidentsayingitwas agroup effort. Thereweresomanypeoplewhoofferedtheirsupportinvariousways and Ican honestlysaythateveryoneinmylifewhilecompletingthisadventuredeserves recognition. Ithank you all. Inparticular, Iwouldliketoacknowledge thefinancialsupport Iwas fortunateto receivefromtheCanadianInstitutes ofHealthResearch andthe WesternRegional TrainingCentre. Theirsupportwasnotonlymonetarybutalsoeducational,providing mewiththeopportunitytotraveltovariousconferences and gainexposuretoother researchers. This travel wasfurtherfacilitatedbythevarioustravelawardsIobtained whichalsocontributedto mylearningexperience. IwouldliketoacknowledgetheManitobaCentreforHealthPolicyforuseofdata containedinthePopulationHealthResearchDataRepositoryunderproject #2010/2011- 06. Theresultsandconclusionsaremyownand noofficialendorsementbythe ManitobaCentrefor HealthPolicy, ManitobaHealth,orotherdataprovidersisintended orshouldbeinferred. Iwouldalsoliketo acknowledgemythesiscommitteeandofferallof you a heartfeltthank you. Eachofyouprovided mewithaverydistinctareaofexpertisethat trulyhelpedshapemythesis. Icannotimaginehavingcompletedthisventurewithout anyof you. Iamso gratefulto you-Alan,CarolandChris–fortheconstructive feedbackand guidancethatyouprovidedalongtheway. Mycommitteewasledbymyadvisor,Michelle;thisis as much your accomplishmentasitismine. Yourencouragementandsupportwereparamountinthe iv completionofmydegree. Thanksto you Iwas givenopportunities totravelandtakepart inconferencesthatIwouldhaveotherwisenothad. Youmadeagreatdifferenceinmy developmentintheareaofCommunityHealthSciences thatwillreflecton myfuture projectsthroughoutmycareer. TheDepartmentofCommunityHealth Sciencesislikenoother. Iamso grateful tomyfellowstudentsfor theirongoingsupportandmotivation. Wehavehelpedeach otherthroughmanymomentsoffrustrationandtheoccasionaldesireto giveup. Friendshipsandbondshavebeenformedoverweekends andeveningsofintensestudying inordertomakeadeadline. Ilookforwardtocontinuingtointeractwithallofyouon a professionalandpersonalbasis. Tothefaculty,Ialsosaythank you. Ireallyhave enjoyedmytimeas aCHSstudentandwouldrecommendourprogramtoeveryone. Though Isometimesdoubtedthatthisthesiswouldeverbefinished,myfamily andfriendsneverdid. Whenfrustrationwouldsinkinafteralongday, you werealways theretolistenandencouragemeto keep going;when Ineededbabysitterstofinishthe lastdetails,youwerethere–thank you. Ilove youall. Ishareallofmy accomplishmentswithmyhusband Danielanddaughter Emilia– youweremy inspirationandmotivation. v TableofContents Abstract................................................................................................................................ii Acknowledgements.............................................................................................................iv TableofContents................................................................................................................vi ListofTables...............................................................................................................viii Listof Figures.................................................................................................................ix ListofCopyrighted Figures............................................................................................xi ListofAppendices..........................................................................................................xi Chapter1-Introduction.......................................................................................................1 Purpose.............................................................................................................................2 StudyObjectives and Hypotheses....................................................................................2 ChapterSynopsis..............................................................................................................4 Chapter1– Introduction...............................................................................................4 Chapter2–TheoreticalFrameworks...........................................................................4 Chapter3–Background and LiteratureReview..........................................................5 Chapter4– Methodsand Analysis...............................................................................5 Chapter5–Results.......................................................................................................6 Chapter6–Discussion.................................................................................................7 Chapter7–Conclusion................................................................................................7 Chapter2–TheoreticalFrameworks...................................................................................9 PopulationHealth Framework.........................................................................................9 Thedeterminantsofhealth.........................................................................................11 Ecological Framework...................................................................................................16 Spatial Framework.........................................................................................................18 Chapter3-Background and LiteratureReview................................................................19 Influenzaand Influenza-likeIllnesses............................................................................20 PandemicInfluenza........................................................................................................26 EpidemiologyofInfluenzainManitoba........................................................................27 Place,SpaceandTime...................................................................................................34 SpatialEpidemiology:DataVisualisation,DataExploration,DataModeling..............36 vi Datavisualisation.......................................................................................................36 Dataexploration.........................................................................................................37 Datamodeling.............................................................................................................38 Chapter4-Methodsand Analysis.....................................................................................41 StudyAreaand StudyPeriod.........................................................................................41 DataSources...................................................................................................................44 StudyPopulation- InclusionCriteria.............................................................................46 StudyPopulation-ExclusionCriteria............................................................................51 Analysis..........................................................................................................................51 PreparationoftheData...................................................................................................52 Objective1–DataVisualisation....................................................................................54 Temporaldistribution.................................................................................................54 Spatialdistribution......................................................................................................55 Objective2–DataExploration......................................................................................57 Objective3–DataModeling.........................................................................................57 StudyVariables...........................................................................................................58 Chapter5-Results.............................................................................................................62 Objective1–DataVisualisation....................................................................................63 Objective2–DataExploration......................................................................................75 Objective3–DataModeling.........................................................................................78 Chapter6-Discussion.......................................................................................................86 Objective1–DataVisualisation....................................................................................87 Objective2–DataExploration......................................................................................90 Objective3–DataModeling.........................................................................................91 StudyLimitations andAssumptions..............................................................................98 Chapter7-Conclusions...................................................................................................102 Bibliography....................................................................................................................107 Appendices.......................................................................................................................116 vii ListofTables Table1–CDC WeekofFirstand Last LaboratoryConfirmedCasesbyStudyYear.....29 Table2-Datasetstobeused............................................................................................45 Table3- ICD-09-CMCodestobeincludedin ILIdefinition......................................47 Table4- ICD-10-CA Codestobeincludedin ILIdefinition.......................................48 Table5–PercentofStudyPopulationbySpecificICDCode.........................................49 Table6–CDCweeksusedfromeach FiscalYearofAdministrativeData.....................50 Table7– ICD–10–CACodesShowingICD–9 –CMCodeEquivalent....................53 Table8- Studyvariables includedinanalysis..................................................................60 Table9- InitialCaseDataforTotal Population...............................................................62 Table10–CaseDatafor StudyPopulationDuringInfluenzaSeason2004/2005– 2008/2009(CDC weeks 39-17)........................................................................................63 Table11–SimpleNegativeBinomialRegression Results..............................................80 Table12-MultipleNegativeBinomialRegression Results............................................82 viii ListofFigures Figure1- Apopulationhealthframework.......................................................................10 Figure2- Thedeterminants ofhealth...............................................................................12 Figure3- Populationhealthpyramid...............................................................................13 Figure4– Manitoba PrematureMortalityRates byHealthDistrictandNeighbourhood Cluster...............................................................................................................................16 Figure5- Laboratoryconfirmedinfluenzacases byCDCweekbyseason.....................30 Figure6- Agedistributionoflaboratoryconfirmedinfluenzacases byseason..............31 Figure7- Agedistributionoflaboratoryconfirmedinfluenzacases for2008/2009season ...........................................................................................................................................31 Figure8- Laboratoryconfirmedinfluenzacases byregionalhealthauthoritybyseason32 Figure9- Laboratoryconfirmedinfluenzacases byseasonandserotype.......................33 Figure10- ManitobaRegionalHealthAuthorities andHealthDistricts.........................42 Figure11- WRHANeighbourhoodClusters...................................................................43 Figure12- TotalNumberof ILIin ManitobaperCDC Weekfrom2004/2005to 2008/2009.........................................................................................................................50 Figure13- TemporalandSpatialVariationofCombinedYears fortheEarlySeason...66 Figure14- TemporalandSpatialVariationofCombinedYears fortheEarly-MidSeason ...........................................................................................................................................67 Figure15- TemporalandSpatialVariationofCombinedYears fortheMidSeason.....68 Figure16- TemporalandSpatialVariationofCombinedYears fortheLateSeason.....69 Figure17- TemporalandSpatialVariationofCombinedYears oftheHealthDistricts 71 Figure18- TemporalandSpatialVariationofCombinedYears oftheNeighbourhood Clusters.............................................................................................................................72 Figure19-CumulativeILIRates forCombinedYearsbyHealthDistrict......................73 Figure20-CumulativeILIRates forCombinedYearsbyNeighbourhood Cluster........74 Figure21- SpatialVariationofCombinedYearsfortheILISeason..............................75 Figure22- Areas ofHighand Low LikelihoodtoClusterAccordingtoSpatialScan Statistic..............................................................................................................................77 ix ListofCopyrightedFigures Figure1- Apopulationhealthframework........................Error!Bookmarknotdefined. Evans,R.,& Stoddart,G.(1990).Producinghealth,consuminghealthcare. Social Scienceand Medicine,1347-1363. Figure3- Populationhealthpyramid................................Error!Bookmarknotdefined. Etches,V., Frank,J.,Di Ruggiero,E., &Manuel, D.(2006). MeasuringPopulation Health:AReviewofIndicators.AnnualReview ofPublicHealth,27:29-55. x
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