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SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Measuring diabetes mortality: Problems & Prospects Chalapati Rao April 2011.

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Presentation on theme: "SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Measuring diabetes mortality: Problems & Prospects Chalapati Rao April 2011."— Presentation transcript:

1 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Measuring diabetes mortality: Problems & Prospects Chalapati Rao April 2011

2 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Outline l Background – Pathophysiology of diabetes mortality – Conventions in coding and statistical presentation – Current understanding of diabetes mortality l Multiple cause of death analyses – Diabetes – underlying cause vs ‘mentions’ – Diabetes and IHD / Stroke – Diabetes and renal disease l Summary of issues l Prospects for consistent and comparable data

3 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Background / context l Diabetes is an increasing public health problem l Measures of incidence / prevalence are difficult to attain for various reasons – Sampling issues / response rates / measurement error l Population level measures of mortality appear straightforward, from national death registration systems

4 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Medical certificate of cause of death

5 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND l Example 1 Cardiac arrest Congestive heart failure Myocardial infarction Metastatic lung cancer Mode of dying Ia Ib II Underlying cause of death: Myocardial infarction Death certification

6 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Definition of underlying Cause of Death l When only one cause: select for tabulation l When several causes: “underlying” = the disease or injury, which initiated the train of morbid events leading directly to death, or the circumstance of the accident or violence which produced the fatal injury.

7 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Rules for ICD Coding l Recommend primary tabulations based on underlying causes (data submitted to WHO Mortality Database) l Rules for selection of underlying causes – General Principle – Selection rules 1 – 3 – Modification rules A – F – Specific rules for individual causes (decision tables ~ several hundred pages ) l CURRENTLY, AUTOMATED CODING SYSTEMS IN SEVERAL COUNTRIES, INCLUDING AUSTRALIA AND USA

8 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Causes of diabetes deaths DIABETES Metabolic complications Direct microvascular changes Associated vascular changes (Atherosclerosis) Contributory cause l Ketoacidosis l Hyperosmolar coma l Hypoglycaemia l Peripheral vascular / neural gangrene → sepsis l Diabetic renal disease l MI l Stroke l ? Diabetic cardiomyopathy l Tuberculosis l Cancer l Pneumonia l etc

9 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Rules for diabetes l Underlying causes coded to three broad categori es – Insulin dependent DM – E10 – Non-insulin dependent DM – E 11 – Unspecified DM – E14 l Each with 9 sub categories with a fourth character extension l. 0 – coma.1 - ketoacidosis l.2 – renal complications.3 – ophthalmic complications l.4 – neurological complications.5 – peripheral circulatory complications l.6 – other specified complications.7 – multiple complications l.8 – unspecified complications.9 – without complications

10 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Table 2: [C1] Distribution of numbers of fourth character diabetes UCOD coded deaths[C1] Fourth character for UCOD E10 – E14 AustraliaUSA 1999200619992004.0 – coma3429688464.1 - ketoacidosis38651,8941,810.2 – renal complications1151311,7301,727.3 – ophthalmic complications754931.4 – neurological complications1112392394.5 – peripheral circulatory complications4975077,6027,616.6 – other specified complications68274254.7 – multiple complications4967794663.8 – unspecified complications3-17755.9 – without complications 2,187 2,838 (78%) 54,799 60,124 (82%) Total deaths with diabetes as UCOD 2,9473,66268,39973,138

11 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Multiple causes of death analysis To explore magnitude of diabetes mortality as a co-morbidity with other conditions in general; and with cardiovascular / renal disease in particular To explore the phenomenon of mortality coded to ‘diabetes without complications’ To assess potential influence of certification / coding practices on statistics

12 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Table 1. Trends in deaths from diabetes (underlying cause and total mentions on death certificate): numbers and percentage of total deaths for Australia (1999 and 2006) and USA (1999 and 2004). Number of deaths (% of all deaths) AustraliaUSA 1999200619992004 Diabetes UCOD 2,947 (2.3%) 3,662 (2.7%) 68,399 (2.9%) 73,138 (3.1%) Diabetes listed on, certificate 9,588 (7.5%) 12,811 (9.6%) 209,679 (8.8%) 225,455 (9.4%) Preliminary data assessment

13 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Observations l Diabetes mentioned in Part II about twice as often as in part 1 l Similar observations in data from Brazil, France, Sweden, and several other European countries l This indicates its higher association with mortality than perceived from underlying cause data l All this occurs in a backdrop of general under reporting of diabetes on death certificates l Diabetes listed as a single cause in only 1- 2% cases, so the deaths coded to ‘DM without complications’ is a misrepresentation of reality

14 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Diabetes and Myocardial Infarction (MI) / Stroke l SPECIAL RULE l If MI / stroke listed as a consequence of diabetes in Part 1, then underlying cause is diabetes l If MI / stroke listed in Part 1, with Diabetes in Part II, then underlying cause is MI / stroke

15 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND l Example 1 Left ventricular failure Myocardial infarction Diabetes Ia Ib 1c II Underlying cause of death: Diabetes Death certification

16 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND l Example 2 Left ventricular failure Myocardial infarction Diabetes Ia Ib 1c II Underlying cause of death: Myocardial infarction Death certification

17 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Diabetes and Myocardial Infarction YearAustraliaUSA UCODPt 2UCOD %UCODPt 2UCOD % 1999 13112312 36% 2616852724 33% 2000 13152345 36%265785202534% 2001 13412400 36%268705152634% 2002 14582452 37%274745086135% 2003 15442291 40%275445000636% 2004 16272235 42%2691647877 36% 2006 16522129 44% l Deaths with MI in Part 1; and diabetes in Part 1 (UCOD) or Part 2

18 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Diabetes and Stroke YearAustraliaUSA UCODPt 2UCOD %UCODPt 2UCOD % 1999 479762 39% 781712769 38% 2000 46375938%77431246238% 2001 51080239%78141245539% 2002 53582839%76581262338% 2003 61279543%74551203938% 2004 64478845%731711793 38% 2006 659862 43% l Deaths with stroke in Part 1; and diabetes in Part 1(UCOD) or Part 2 l Diabetes is being increasingly listed in Part 1, thereby augmenting its magnitude in underlying cause mortality statistics

19 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Other evidence l Similar variations observed in other countries (Taiwan, Sweden) – South Africa is quite different with 98% of diabetes related deaths having diabetes recorded in Part 1 l Variation tested through clinical vignettes describing mortality from cardioavascular disease in diabetics – Identified high degree of subjectivity in physcians, in the practice of listing Diabetes in part 1 vs Part 2, with concomitant MI / stroke

20 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Clinical / pathological perspective l ‘Diabetes predisposes to cardiovascular diseases’ – Harrison’s Principles of Internal Medicine; 17 th Edition l ‘Diabetes mellitus, whether type 1 or type 2, is a very strong risk factor for the development of coronary artery disease (CHD) and stroke ’ – Hurst: The Heart – 12 th Edition l ‘Diabetes mellitus induces hypercholesterolemia and a markedly increased predisposition to atherosclerosis’ – Robbins Pathologic Basis of Disease, 6 th edition l The American Heart Association has designated DM as a major risk factor for cardiovascular disease (same category as smoking, hypertension, and hyperlipidemia)

21 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Inferences l Inconsistency in certification practices compounded by ambiguity in coding rules l As a result, Diabetes / CVD statistics based on underlying causes not readily comparable across countries, or over time

22 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Diabetes with renal complications l Clear relationship from pathological perspective – Microvascular and basement membrane changes in glomerulus producing distinctive Kimmelstein Wilson lesions PLUS atherosclerotic changes in renal arterial vessels l Designated code in ICD rules – BUT – some interesting fine print…..

23 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Table 2: [C1] Distribution of numbers of fourth character diabetes UCOD coded deaths[C1] Fourth character for UCOD E10 – E14 AustraliaUSA 1999200619992004.0 – coma3429688464.1 - ketoacidosis38651,8941,810.2 – renal complications 115 (3.9%) 131 (3.6%) 1,730 (2.5%) 1,727 (2.4%).3 – ophthalmic complications754931.4 – neurological complications1112392394.5 – peripheral circulatory complications4975077,6027,616.6 – other specified complications68274254.7 – multiple complications4967794663.8 – unspecified complications3-17755.9 – without complications 2,187 2,838 (78%) 54,799 60,124 (82%) Total deaths with diabetes as UCOD 2,9473,66268,39973,138

24 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Coding rules for ‘DM with renal complications’ l Coded as underlying cause IF any of the following terms listed in part 1 of the death certificate – Diabetic nephropathy – Kimmelstein Wilson Disease – Intracapillary Glomerulosclerosis

25 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Specific additional rule l Coded to DM with renal complications IF l A) the death certificate lists DM in part 1; AND l B) with any of the following listed as a consequence, in Part 1 – Unspecified disorder of the kidney or ureter (N28.9) – chronic nephritic syndrome (N03) – nephrotic syndrome (N04) – unspecified nephritic syndrome (N05) or – unspecified contracted kidney (N26) l RENAL FAILURE (N17-N19) listed as a consequence of Diabetes is not considered as Diabetes with renal complications

26 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Research hypothesis l Certifying physicians are more likely to write ‘RENAL FAILURE’ on death certificates, rather than the more complex terms listed in the rules l ‘Diabetes with renal failure’ can be considered as ‘diabetic renal disease’ l Question: What do the multiple causes of death data tell us about mortality from diabetic renal disease?

27 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Multiple cause of death data 1. Extract all deaths coded to DM as underlying cause 2. Create subset of deaths coded to ‘DM with renal complications’ 3. THEN Screen all remaining DM UCOD deaths, for renal failure listed as a consequence of DM in Pt 1, to create additional deaths subsets 4. Additional deaths A: Deaths with UCOD -DM without complications; but with Renal failure listed in Pt 1 5. Additional deaths B: Deaths coded to other DM UCOD categories, but with renal failure listed in Pt 1

28 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Deaths from diabetic renal disease Deaths AustraliaUSA 1999200619992004 Diabetes with renal complications 115 1311,7301,727 Additional deaths ‘A’ 301*57711,54313,739 Additional deaths ‘B’ 118 # 1692,1662,241 Total diabetes UCOD 2,9473,66268,39973,138 l * out of 2187 deaths coded to DM without complications l # out of 645 deaths coded to diabetes with other categories of complications except renal or *

29 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Comparison of underlying vs mulitple cause rates Age-standardised death rates (per 100,000)* USA Australia 19992004% change 19992006% change Underlying cause rate (UCR) 0.680.62 -7.7 0.670.64 -5.3 Multiple cause rate 1 (MCR1) 5.25.6 7.3 2.53.4 37.7 Rate ratio† (95% CI) 7.7 (7.3 – 8.1) 8.9 (8.5 – 9.4) − 3.7 (3.0 – 4.6) 5.4 (4.5 – 6.5) − Multiple cause rate 2 (MCR2) 6.16.45.63.24.334.2 Rate ratio† (95% CI) 9 (8.5 – 9.4) 10.3 (9.8 – 10.8) − 4.7 (3.9 – 5.8) 6.7 (5.6 – 8.0) − l *Standardised to Australian population in 2006. l † To the UCR

30 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Time trends

31 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Summary l Conventional mortality statistics based on underlying causes mask true patterns of mortality from diabetes and its complications l Issues in certification, coding and statistical presentation result in this situation l These need to be addressed, to improve prospects of more realistic understanding of diabetes mortality, given the impending epidemic in the Asia Pacific region

32 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND Global availability of cause of death data : 2001 The boundaries and names shown and the designations used on this map do not imply the expression of any opinion whatsoever on the part of the World Health Organization concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dotted lines on maps represent approximate border lines for which there may not yet be full agreement. © WHO 2003. All rights reserved Vital Registration

33 SCHOOL OF POPULATION HEALTH THE UNIVERSITY OF QUEENSLAND References / acknowledgements 1. Rao C, Adair T, Bain C, Doi SA. Mortality from diabetic renal disease: a hidden epidemic. Eur J Public Health. 2011 Jan 18. [Epub ahead of print] 2. Adair T, Rao C. Changes in certification of diabetes with cardiovascular diseases increased reported diabetes mortality in Australia and the United States. J Clin Epidemiol. 2010 Feb;63(2):199-204.


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