Mortality attributable to diabetes: Estimates for the year 2010

1. Introduction 

Mortality is an important measure of population health and is often used to assign priorities in health interventions. Estimating mortality due to diabetes has been challenging because more than a third of countries of the world have no reliable data available on mortality and also because existing routine health statistics have been shown to underestimate mortality from diabetes [1]. The latter is largely because persons with diabetes most frequently die of cardiovascular disease or renal failure, rather than a complication specific to diabetes [2]. Cause specific mortality statistics are based on the underlying cause of death recorded on the death certificate. In cases of cardiovascular disease death in particular diabetes is frequently not mentioned at all, or if it is, it is not specified as the underlying cause of death [3]. The problem of assessing the true mortality contribution of a disease is not unique to diabetes. Complex and resource-demanding methods that combine vital registration, results of population-monitoring laboratories and epidemiologic studies, have been developed for estimating mortality attributable to some conditions deemed to be of public health importance (AIDS, tuberculosis), but equivalent methods have not been developed for diabetes [4].

To provide a more realistic estimate of the burden of mortality attributable to diabetes than is available from routine sources of health statistics, a modelling approach has been used recently for the years 2000 and 2007 [5], [6]. This study uses similar methodology to estimate the number of deaths attributable to diabetes in the year 2010.

2. Methods 

The number of deaths attributable to diabetes was calculated using the following input data:

Table 1 shows the age-specific relative risks of mortality in people with diabetes compared to those without from the different studies. The table also indicates which study results were used for different International Diabetes Federation regions.

Table 1. Age- and sex-specific relative risks of death used to estimate the proportion of all deaths attributable to diabetes.

	Age group (years)	DECODE Studya		DECODA Studyb [Indians in Mauritius and Fiji]		DECODA Studyc [All]		Taiwan Studyd		NHANESe
		Males	Females	Males	Females	Males	Females	Males	Females	Males	Females
	20–29	3.66	6.05	3.40	5.12	3.70	5.95	5.42	4.68	3.08	3.20
	30–39	3.38	5.41	3.50	4.98	3.30	5.61	5.26	4.64	4.60	3.10
	40–49	1.85	3.14	2.60	3.65	1.95	3.41	4.24	4.25	2.80	2.80
	50–59	1.63	2.64	2.30	3.29	1.65	2.73	3.02	3.44	2.00	2.60
	60–69	1.60	2.04	1.60	2.51	1.62	2.08	2.22	2.58	1.65	2.10
	70–79	1.39	1.79	1.50	2.42	1.40	1.78	1.46	1.61	1.40	1.60

a Used for Europe, Australia and New Zealand. b Used for South Asia. c Used for Africa and Eastern Mediterranean. d Used for Western Pacific (except Australia and New Zealand). e Used for North and South America and the Caribbean.

DisMod II, a software programme developed for the Global Burden of Disease 2000 Study [11], was used to calculate the number of deaths attributable to diabetes in persons 20–79 years old, i.e. the number of deaths among those with diabetes over and above deaths expected according to underlying mortality rates. DisMod II smoothes out the age-specific relative risks of death available from the different studies and calculates what proportion of all deaths is attributable to diabetes using Miettinen's formula for the population-attributable fraction [12].

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.

3. Results 

The numbers of excess deaths due to diabetes are presented by IDF Regions in Table 2. It is predicted that almost 4 million deaths in 2010 could be attributed to diabetes, which is 6.8% of global (all ages) all-cause mortality. In all regions, bar one, roughly 10% or more of deaths in the age group 20–79 were attributable to diabetes, with the highest proportion (15.7%) being in North America, reflecting both a high prevalence of diabetes and a relatively elderly population. Africa is the region with the lowest proportion of deaths attributable to diabetes in adults. But even here diabetes accounted for over 1 in 20 deaths, representing over a third of a million deaths in 2010.

Table 2. Number of deaths attributable to diabetes in age group 20–79 years in the year 2010.

	IDF Region	Number of deaths attributable to diabetes in age group 20–79 years	Percentage of all-cause deaths attributable to diabetes in age group 20–79 years
	Africa	332,584	6.0
	Eastern Mediterranean and Middle East	294,037	11.5
	Europe	634,054	11.0
	North America	313,208	15.7
	South and Central America	171,303	9.5
	South-East Asia	1,142,914	14.3
	Western Pacific	1,074,955	9.7

Table 3 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 2.6 to 5.2 million. If the relative risk is 20% lower, 4.5% of total mortality can be attributed to diabetes, ranging from 3.9% in the African Region, to 10.1% in the South-East Asian Region. If the relative risk of dying is 20% higher, 9.2% of total mortality can be attributed to diabetes, ranging from 7.9% in the African Region to 21% in the North American Region.

Table 3. Number of deaths attributable to diabetes if the true relative risk of dying is 20% lower and 20% higher than estimated in the cohort studies.

	IDF Region	Relative risk 20% lower	Relative risk 20% higher
	Africa	217,914	441,267
	Eastern Mediterranean and Middle East	181,898	392,806
	Europe	345,126	882,648
	North America	186,974	419,104
	South and Central America	91,659	239,358
	South-East Asia	802,914	1,461,543
	Western Pacific	721,358	1,386,849

The highest number of deaths attributable to diabetes is expected to occur in countries with large populations—1,008,000 deaths in India, 575,000 in China, 231,000 in The United States of America and 182,000 in The Russian Federation. The number of deaths is also higher in women than in men, and diabetes makes 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 4a, Table 4b).

Table 4a. Number of male deaths attributable to diabetes in the year 2010 and percentage of all-cause mortality by age group and IDF Region.

	IDF Region	Age group (years)
		20–29	30–39	40–49	50–59	60–69	70–79
	Africa	11,141 (3.1)	27,984 (5.3)	21,918 (4.2)	21,405 (4.3)	23,708 (4.9)	16,018 (3.4)
	Eastern Mediterranean and Middle East	4,986 (3.4)	12,414 (9.0)	15,874 (9.1)	26,911 (9.6)	33,342 (10.1)	23,516 (6.0)
	Europe	5,860 (4.3)	17,216 (8.0)	23,342 (6.0)	52,692 (7.4)	85,933 (10.4)	112,557 (9.0)
	North America	2,090 (4.2)	7,104 (11.7)	16,396 (13.9)	30,136 (13.6)	43,555 (14.0)	41,726 (10.6)
	South and Central America	1,527 (1.5)	8,584 (8.6)	13,744 (10.6)	19,845 (10.4)	22,520 (8.9)	17,273 (5.5)
	South-East Asia	13,908 (3.9)	41,924 (10.0)	70,849 (12.5)	130,209 (14.9)	105,092 (9.6)	114,922 (9.6)
	Western Pacific	9,976 (3.6)	33,198 (9.4)	96,470 (14.4)	170,141 (14.4)	180,205 (10.4)	98,276 (4.0)

Table 4b. Number of female deaths attributable to diabetes and its percentage of all-cause mortality by age group and IDF Region.

	IDF Region	Age group (years)
		20–29	30–39	40–49	50–59	60–69	70–79
	Africa	25,256 (6.1)	50,422 (9.5)	37,373 (8.7)	35,970 (9.0)	30,895 (7.1)	30,495 (6.0)
	Eastern Mediterranean and Middle East	6,021 (6.3)	15,867 (16.2)	23,217 (19.3)	40,942 (22.2)	44,242 (17.7)	46,707 (13.1)
	Europe	1,131 (2.8)	4,966 (6.9)	14,706 (9.5)	50,606 (15.0)	76,976 (15.4)	188,069 (16.0)
	North America	634 (3.2)	3,634 (11.4)	15,776 (22.2)	41,362 (29.4)	58,544 (25.9)	52,252 (15.1)
	South and Central America	456 (1.5)	1,937 (4.6)	7,833 (10.7)	20,638 (17.1)	29,580 (16.6)	27,367 (10.1)
	South-East Asia	20,901 (7.1)	42,680 (15.6)	67,618 (19.0)	137,823 (24.0)	168,370 (20.1)	228,618 (20.2)
	Western Pacific	3,032 (2.3)	15,742 (7.2)	61,207 (14.3)	127,138 (18.0)	161,150 (15.3)	118,420 (6.2)

4. Discussion 

While there has been a documented decline in the morbidity and mortality of some chronic noncommunicable diseases in some countries [13], 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 [14].

Comparing these estimates of mortality attributable to diabetes to those for the year 2007 [6], obtained by using the same relative risks of dying but different diabetes prevalence estimates and all-cause mortality rates, the number of deaths attributable to diabetes has increased by 5.5%. This increase is on account of a 29% increase in the number of deaths due to diabetes in the Northern American Region, a 12% increase in the South-East Asian Region and an 11% increase in the Western Pacific Region. These increases can be explained by an increase in diabetes prevalence in some highly populated countries in each region (USA, India and Indonesia), particularly in females. In the other regions, the number of deaths attributable to diabetes has remained similar to the estimates for the year 2007.

The consistently higher contribution of diabetes to total mortality in women is partly explained by higher relative risks of mortality in women with diabetes compared to women without diabetes than found in men, in most regions and age groups (Table 1). This in part reflects that overall mortality in men is higher than in women. In addition, in the oldest age group there tend to be more women with diabetes than men, and the numbers of deaths attributable to diabetes in women are therefore higher in most regions (Table 4a, Table 4b).

The reliability of these estimates rests on several assumptions, as discussed below.

Conflict of interest 

The authors state that they have no conflict of interest. The views expressed within this paper are those of the authors and not necessarily those of WHO.