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Update of mortality attributable to diabetes for the IDF Diabetes Atlas: Estimates for the year 2011

      1. Introduction

      Mortality is one of the key measures for understanding the burden of a disease, its progression, and to design appropriate health interventions. However, vital registration systems are often lacking to report cause-specific mortality. Diabetes is an especially challenging disease to estimate true mortality since most people die of a related complication such as cardiovascular disease or renal failure [
      • Morrish N.J.
      • Wang S.L.
      • Stevens L.K.
      • Fuller J.H.
      • Keen H.
      Mortality and causes of death in the WHO Multinational Study of Vascular Disease in Diabetes.
      ]. As a result, diabetes is often not listed as the underlying cause-of-death and is consistently underestimated in routine health statistics [
      • Fuller J.H.
      • Elford J.
      • Goldblatt P.
      • Adelstein A.M.
      Diabetes mortality: new light on an underestimated public health problem.
      ]. A methodology has been developed using a modelling approach to provide a more realistic estimate of the burden of attributable mortality to diabetes [
      • Roglic G.
      • Unwin N.
      Mortality attributable to diabetes: estimates for the year 2010.
      ,
      • Roglic G.
      • Unwin N.
      • Bennett P.H.
      • Mathers C.
      • Tuomilehto J.
      • Nag S.
      • et al.
      The burden of mortality attributable to diabetes: realistic estimates for the year 2000.
      ,
      Diabetes atlas.
      ]. This report uses the same methodology to update estimates for the year 2011 and integrate new studies on the prevalence of diabetes [
      • Whiting D.R.
      • Guariguata L.
      • Weil C.
      • Shaw J.
      IDF diabetes atlas: global estimates of the prevalence of diabetes for 2011 and 2030.
      ].

      2. Methods

      The methods to derive these estimates have been described by Roglic and Unwin [
      • Roglic G.
      • Unwin N.
      Mortality attributable to diabetes: estimates for the year 2010.
      ]. Briefly, the number of deaths attributable to diabetes uses the following inputs: WHO life tables for 2008 for the expected number of deaths; country-specific diabetes prevalence by age and sex for the year 2011; age and sex-specific relative risks of death for persons with diabetes compared to those without diabetes as used in the previous publication [
      • Roglic G.
      • Unwin N.
      Mortality attributable to diabetes: estimates for the year 2010.
      ,
      • Whiting D.R.
      • Guariguata L.
      • Weil C.
      • Shaw J.
      IDF diabetes atlas: global estimates of the prevalence of diabetes for 2011 and 2030.
      ]. These inputs are used to model the estimates using DisModII, a programme developed for the Global Burden of Disease study from 2000 and then Miettinen's formula for the population-attributable fraction is used to calculate the number of deaths attributable to diabetes in people 20–79 years of age [
      • Miettinen O.S.
      Proportion of disease caused or prevented by a given exposure, trait or intervention.
      ].
      Cohort studies estimate the true population relative risk of dying with some uncertainty, and measures of precision, such as confidence intervals, around the estimates were not available for all of the studies used in the calculations of the number of deaths. In order to reflect the uncertainty in the relative risk estimates, sensitivity analyses were conducted assuming that the true relative risks were 20% lower and 20% higher than those found in each cohort study. The relative risks used for these estimates in each region are reported in Roglic and Unwin [
      • Roglic G.
      • Unwin N.
      Mortality attributable to diabetes: estimates for the year 2010.
      ].

      3. Results

      The numbers of excess deaths due to diabetes are presented by International Diabetes Federation (IDF) Regions in Table 1. It is predicted that almost 4.6 million deaths in 2011 could be attributed to diabetes, which is 8.2% of global (all ages) all-cause mortality. With the exception of the Africa Region, 10% or more of deaths in the age group 20–79 were attributable to diabetes, with the highest proportion (15.3%) being in the Western Pacific Region. Africa is the region with the lowest proportion of deaths attributable to diabetes in adults, but even there diabetes accounted for over 1 in 20 deaths.
      Table 1Number of deaths attributable to diabetes in age group 20–79 years in the year 2011.
      IDF RegionNumber of deaths attributable to diabetes in age group 20–79 yearsPercentage of all-cause deaths attributable to diabetes in age group 20–79 years
      Africa344,4626.1
      Middle East and North Africa278,57510.3
      Europe597,79510.1
      North America and the Caribbean280,82713.8
      South and Central America227,14712.3
      South-East Asia1,156,01914.5
      Western Pacific1,708,31515.3
      Table 2 shows the number of deaths attributable to diabetes if the relative risks of dying are assumed to be 20% lower and 20% higher than what was estimated in the cohort studies. With these assumptions the global number of deaths attributable to diabetes ranges from 3 to 6 million. If the relative risk is 20% lower, 5.1% of total mortality can be attributed to diabetes. In the age group 20–79 years the percentage of deaths attributable to diabetes ranges from 4.1% in the Africa Region, to 10.4% in the Western Pacific Region. If the relative risk of dying is 20% higher, 10.1% of total mortality can be attributed to diabetes. In the age group 20–79 years the percentage of deaths attributable to diabetes ranges from 8.0% in the Africa Region to 19.5% in the Western Pacific Region.
      Table 2Number of deaths attributable to diabetes in the year 2011 and % of deaths attributable to diabetes in age group 20–79 years, if the true relative risk of dying is 20% lower and 20% higher than estimated in the cohort studies.
      IDF RegionRelative risk 20% lower number of deaths (% of all deaths in age group 20–79 years)Relative risk 20% higher number of deaths (% of all deaths in age group 20–79 years)
      Africa229,905 (4.1)449,263 (8.0)
      Middle East and North Africa166,942 (6.2)378,245 (14.1)
      Europe327,987 (5.6)832,296 (14.0)
      North America and the Caribbean166,176 (8.2)379,519 (18.3)
      South and Central America123,776 (6.7)312,076 (16.9)
      South-East Asia799,043 (10.1)1,462,685 (18.6)
      Western Pacific1,158,050 (10.4)2,175,520 (19.5)
      The highest number of deaths attributable to diabetes occurred in countries with large populations: 1,132,000 in China, 983,000 deaths in India, 217,000 in The Russian Federation and 180,000 in The United States of America. The number of deaths is also higher in women than in men, and diabetes generally accounts for a higher proportion of all deaths in women than in men, reaching up to a quarter of all deaths in middle-aged women in some regions (Table 3a, Table 3b).
      Table 3aNumber of male deaths attributable to diabetes in the year 2011 and its percentage of all-cause mortality by age group and IDF Region.
      IDF RegionAge group (years)
      20–2930–3940–4950–5960–6970–79
      Africa15,856 (4.6)38,081 (7.1)21,799 (4.2)19,635 (3.9)24,597 (4.7)18,015 (3.7)
      Middle East and North Africa8491 (5.7)17,318 (11.9)18,294 (10.3)29,286 (10.4)38,357 (10.8)29,938 (6.7)
      Europe2917 (2.1)13,438 (6.1)22,733 (5.9)57,721 (8.0)86,292 (10.2)98,229 (7.7)
      North America and the Caribbean2394 (4.7)11,572 (19.0)21,314 (18.1)34,892 (15.5)42,375 (13.1)38,074 (9.3)
      South and Central America1800 (1.8)9556 (9.6)15,806 (12.1)24,127 (12.3)28,551 (10.9)23,479 (7.2)
      South-East Asia12,561 (3.5)51,554 (11.9)99,446 (17.1)169,788 (19.2)105,997 (9.6)65,323 (5.6)
      Western Pacific19,436 (6.9)52,945 (15.2)148,232 (22.0)269,538 (22.2)301,681 (17.2)181,258 (7.6)
      Table 3bNumber of female deaths attributable to diabetes in the year 2011 and its percentage of all-cause mortality by age group and IDF Region.
      IDF RegionAge group (years)
      20–2930–3940–4950–5960–6970–79
      Africa33,578 (8.4)57,843 (10.9)33,248 (7.9)30,733 (7.6)26,630 (5.9)24,446 (4.8)
      Middle East and North Africa9145 (9.2)14,739 (14.2)15,322 (12.2)25,959 (13.6)31,650 (12.1)41,076 (11.0)
      Europe1319 (3.2)6783 (9.3)17,594 (11.5)56,654 (16.5)74,953 (14.7)159,180 (13.3)
      North America and the Caribbean984 (5.0)3445 (11.0)11,685 (16.6)29,786 (20.9)42,928 (18.3)41,377 (11.8)
      South and Central America735 (2.5)3327 (7.9)11,778 (15.9)28,909 (23.3)40,390 (21.9)38,730 (13.9)
      South-East Asia23,560 (3.5)50,240 (11.9)79,740 (17.0)149,921 (19.2)167,394 (9.6)180,296 (5.6)
      Western Pacific4901 (3.6)24,228 (11.2)86,888 (20.2)175,244 (24.5)238,409 (22.0)205,555 (10.7)

      4. Discussion

      While there has been a documented decline in the morbidity and mortality of some non-communicable diseases in some countries [
      • Tunstall-Pedoe H.
      • Kuulasmaa K.
      • Mahonen M.
      • Tolonen H.
      • Ruokokoski E.
      • Amouyel P.
      Contribution of trends in survival and coronary-event rates to changes in coronary heart disease mortality: 10-year results from 37 WHO MONICA project populations. Monitoring trends and determinants in cardiovascular disease.
      ], no such decline has been reported for diabetes. Wherever measured, the prevalence seems to be increasing. Although some developed countries have documented an improved survival of persons with diabetes, the increased prevalence is most likely due to increased incidence rather than improved survival [
      • Colagiuri S.
      • Borch-Johnsen K.
      • Glumer C.
      • Vistisen D.
      There really is an epidemic of type 2 diabetes.
      ].
      Estimates of deaths attributable to diabetes for 2011 have increased by 15.9% compared to those for 2010 using the same methods and incorporating new estimates of prevalence [
      • Roglic G.
      • Unwin N.
      Mortality attributable to diabetes: estimates for the year 2010.
      ]. The increase is largely due to increases found in the prevalence estimates and especially in the Western Pacific which saw a 59% increase in deaths due to diabetes [
      • Whiting D.R.
      • Guariguata L.
      • Weil C.
      • Shaw J.
      IDF diabetes atlas: global estimates of the prevalence of diabetes for 2011 and 2030.
      ] mostly due to new prevalence estimates from China.
      Obtaining accurate estimates of mortality attributable to diabetes with currently available data is difficult, and any attempt will be based on a set of assumptions. The estimates of the number of deaths in this study should be considered just that, estimates rather than accurate measures. However, it is highly plausible that the figures presented here are closer to the truth than estimates derived from routine sources of health statistics which systematically underestimate the burden of mortality due to diabetes [
      • Fuller J.H.
      Mortality trends and causes of death in diabetic patients.
      ].
      The estimated excess number of deaths attributable to diabetes seems to be considerable and of a similar order of magnitude as deaths due to several infectious diseases that receive a lot of attention from policy makers, researchers, donors and the general public [
      AIDS epidemic update: December 2007.
      ,
      Global tuberculosis control: epidemiology, strategy, financing: WHO report 2009.
      ]. Diabetes contributes substantially to premature adult mortality and close to half of all deaths occurred in people under the age of 60. A substantial proportion of these premature deaths are potentially preventable through public health action directed at primary prevention of diabetes in the population and improvement of care for all people with diabetes to prevent premature mortality [
      Preventing chronic diseases: a vital investment.
      ].

      Conflict of interest

      The authors state that they have no conflicts of interest.

      Acknowledgments

      This work would not have been possible without the continued contribution and support of Dr. Gojka Roglic and Profesor Nigel Unwin on whose original methods this update is based.

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