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The effect of the ‘Polypill’ on mortality in general practice

This presentation provides an overview of the electronic database used for the study and describes the research conducted to determine the effect of the 'Polypill' on mortality in patients with Coronary Heart Disease. The QRESEARCH and GPRD databases were utilized for this study, which is relevant for epidemiological studies, case control studies, cohort studies, and cross-sectional surveys. The preliminary results show that patients on a combination of three or four drugs had a significantly lower risk of death.

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The effect of the ‘Polypill’ on mortality in general practice

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  1. The effect of the ‘Polypill’ on mortality in general practice Dr Julia Hippisley-Cox Gozo October 2004

  2. Goals of presentation • To given an over view of electronic database used for the study (QRESEARCH) • To describe research to determine effect of the ‘Polypill’ on mortality in patients with CHD

  3. GP databases in the UK • Several different database available • Oldest and most well known GPRD • QRESEARCH new key databases • Both derived from GP clinical data • Both available for access by researchers • Both are an international resource

  4. QRESEARCHWhat is it? • QR is result of a not-for-profit partnership between UoN & EMIS [supplies > 60% all practices] • Patient level consolidated database • Longitudinal data for up to 16 years • Validated against external and internal measures

  5. Qresearch Coverage • 468+ practices • UK wide • > 5 in every SHA • Approx 7.4 million patients including those who died, left and still registered • 3.3 million current patients • Now the largest such database in the world (unless anyone here knows otherwise!)

  6. Data contents • Socio-demographics • Diagnoses • Clinical values • Laboratory tests • Prescription data • Consultation data • Category of clinician entering data

  7. QRESEARCH Research service • We will provide a service to • Bona fide academics • With original research question • With MREC • With freedom to publish • Who agree to • Acknowledge source data • use it for purpose only • not pass it on

  8. What type of research can we use it for? • Best for epidemiological studies • Case control studies • Cohort studies • Cross sectional survey • Modelling

  9. Things we cant do: • Track back to patients • Track back to practices • Randomise patients or practices • Link with external data sources eg questionnaire, genetics • This is where other systems come in • THIN • e-GRID • UK Biobank

  10. Aims of research project • To determine the effect of the ‘Polypill’ on mortality in CHD patients • Polypill = aspirin + beta blockers + ACE inhibitors + statins

  11. Background to project • Good evidence from individual trials for benefits of individual drugs in 2’ prevention CHD • Enthusiasm for ‘Polypill’ for all patients over 55 years though no direct evidence benefits stack up • Drugs may interact with drugs or other comorbidity

  12. Design & setting • Design • Open cohort study with case control analysis • Setting • 1.18 million patients registered with 89 QRESEARCH practices on 1st Jan 1996 • All practices had a minimum of 8 years of complete computerised data

  13. Study cohort • All patients with a 1st diagnosis of CHD between 1st Jan 96 and 31 Dec 2003 • Study period chosen as statins only in common use after Jan 96

  14. Cases & controls • Cases were CHD patients who died during study period • Controls were CHD patients who didn’t die matched for • Age • Year of birth • Sex • Four controls per case

  15. Index date • Assigned index date to each case [date of death] • Assigned same date to matched controls • Reviewed medical & drug history prior to this date

  16. Outcomes • Odds ratio (95% CI) for all cause mortality in cases vs controls • Exposure • combinations of aspirin, statins, beta blockers and ACE inhibitors • Adjusted for • Comorbidity (MI, Diabetes, hypertension, CCF) • Smoking • obesity • deprivation

  17. Statistics • Conditional logistic regression using STATA v8.2 • Examined for 2 way interactions • drug*drug • drug*disease • Included significant interactions in model • Selected p < 0.01

  18. PRELIMINARY RESTULS study population • 1.17 million patients in population • 13,029 patients with CHD • 2,266 deaths • So 2,266 cases + 9064 matched controls

  19. Comparison with 4S study • Patients on statins had 37% lower risk of death c.f. those not on statins • This is similar to the 30% reduction in risk reported in 4S study • Marginally greater benefit as our population higher risk than trial population

  20. Odds ratio for death * Adjusted for CCF, diabetes, hypertension, MI, smoking, obesity, deprivation etc

  21. In other words • Despite adjustment for comorbidity, patients on combination of : • 3 drugs had 57% lower risk of death • 4 drugs had 37 % lower risk of death • Combination without ACE was better

  22. Discussion of methodology • Case control study but • Very large sample • No recall bias • No selection bias • Misclassification unlikely as drugs all prescribed except aspirin which is also OTC

  23. Possible explanations • We found significant statistical interaction between ACEI and statins • Possible explanations • ? misclassification of CCF (but no interaction between other drugs) • ? Chance finding • Whatever, study challenges assumptions that benefits automatically stack up in ‘real life populations’

  24. Next Steps • Thank you for listening • Ideas and questions welcome!

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