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EDITORIAL
Public health and prevention of blindness in
diabetes
The world is facing an epidemic of diabetes mellitus
[1].
Currently, more than 250 million people in the world have dia-
betes and it is predicted that this number will double in a little
over 20 years
[2–3]. The epidemic is not evenly distributed
around the world. While the world-wide prevalence of diabetes
is 3–4%, several countries and regions experience a prevalence
rate of diabetes of well over 10%. This includes some countries
in the Middle East, where in some cases, the prevalence of dia-
betes among middle aged adults exceed 16%
[4].
Diabetic retinopathy is a relatively new disease. Before the
discovery of insulin, less than 100 years ago, it was virtually
unknown. Diabetic retinopathy entered the medical literature
towards the middle of the twentieth century as more diabetics
survived long enough to develop the disease. In the latter part
of twentieth century, diabetic eye disease rapidly became an
important cause of blindness. Epidemiological studies have
shown that about 1/3rd of type 2 diabetics and every other
type 1 diabetic patient is likely to develop sight threatening
retinopathy within their life time. Sight threatening retinopa-
thy, i.e. diabetic macular edema and/or proliferative diabetic
retinopathy represents a significant threat to vision, and
requires medical intervention to reduce risk of the vision loss
and blindness
[5].
Blindness from diabetes soared in the latter part of the 20th
century. In Sweden, in the 1980s, it was reported that 4.4% of
type 1 and 1.4% of type 2 diabetic patients were legally blind,
with an additional 4.9% and 7.2% respectively with reduced
vision
[6]. These studies may represent a peak in blindness risk
for diabetics. This is before systematic screening and preven-
tive laser treatment was instituted in Scandinavian countries.
From Wisconsin USA, it has been also reported a 10 year inci-
dence of diabetic blindness of about 2% in type 1 and 4–5% in
type 2, with an additional 9% and 24–37% having visual
impairment [7].
Let us take as an example a hypothetical country with 2
million diabetic patients, mostly with type 2 diabetes. About
1/3rd of this group would be expected to develop sight threat-
ening retinopathy within their lifetime, and in the absence of
early diagnosis and optimal treatment, 50% of these are likely
to suffer vision loss. This worst case scenario would indicate
between 3 and 400,000 current diabetic patients having
reduced vision or blindness. If we look at the American epi-
demiology
[7], we might expect about 100,000 people to
become legally blind, and 5–700,000 to suffer from milder
visual impairment, whereas the Scandinavian statistics would
predict slightly lower rates. While the actual outcome also
depends on the overall quality of diabetes care, the availability
of ophthalmic care for those with eye symptoms and tertiary
eye care, this gives an idea of the overall scope of the problem.
Such a rate of blindness is not only a tragedy for the individ-
uals involved and a major problem for the health system,
but an economic burden on society, which needs to support
a large number of people who are unable to work because of
reduced vision.
Retinal photocoagulation has proved to be effective in
reducing the risk of vision loss and blindness, particularly in
proliferative diabetic retinopathy (DRS) and also in clinically
significant diabetic macular edema
[8]. Recently, intravitreal
VEGF antibodies have been reported to be a valuable treat-
ment modality for diabetic macular edema
[9,10]. Careful con-
trol of blood pressure, glucose and other metabolic parameters
also plays a significant role in the treatment of diabetic eye
disease.
The key to successful photocoagulation in diabetic
retinopathy is the timing of the treatment. Optimally, patients
receive retinal photocoagulation in the early stages of prolifer-
ative diabetic retinopathy or diabetic macular edema. At this
point in time, treatment is much more likely to succeed than
if the retinopathy were to be more advanced. Since patients
have no or minimal symptoms of early sight threatening
retinopathy, the only way to diagnose sight threatening
retinopathy in its early stages, and ensure the optimal timing
of treatment, is to systematically look for this disease through
screening examinations. This approach started in the 1980s,
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and has enjoyed enormous success [5,11,12]. Diabetic patients
were scheduled for an annual screening for retinopathy, either
through a standard eye examination with dilated pupils by an
ophthalmologist, or through fundus photography, where the
images were read by expert ophthalmologists. In both cases,
those diabetic patients who were diagnosed with sight threat-
ening retinopathy were referred to laser treatment. It was felt
at that time that annual screening examinations were adequate
for the diabetic group and experience has shown that this
approach resulted in an enormous reduction in the prevalence
of diabetic blindness [5]. Reports from the Nordic countries
now indicate the prevalence of blindness, which is considerably
lower than reported in the 1980s. Zoega reported a 0.3% blind-
ness prevalence in diabetic patients in Iceland
[13]. Olafsdottir
et al. reported about the same in a Swedish population
[14],
and Jeppesen and Bek report 0.6 and 1.5% prevalence of legal
blindness in a type 1 and 2 diabetic population in Denmark
[15]. Backlund et al. reported a one third reduction in diabetic
blindness with screening in Stockholm
[16], while Henricsson
et al. reported that the yearly incidence of new blindness was
1 per 1000 in a Swedish diabetic population in a public health
screening program
[17].
The public health approach, with regular eye screening, has
significantly reduced diabetic blindness in Nordic countries. At
the same time, diabetic eye disease remains a leading cause of
blindness in the 20–60 year age-group, and one of the most
common causes of blindness overall in many countries around
the world, including the United States
[18].
Diabetic retinopathy usually develops 5–15 years after the
onset of disease
[19]. In countries where the prevalence of dia-
betes mellitus is rising rapidly, many individuals, relatively
speaking, will have a short duration of diabetes and may not
yet have developed serious retinopathy. The rise in sight
threatening retinopathy and vision loss follows diabetes epi-
demic with a lag time of approximately 10 years. This delay
is a double edged sword. On the one hand, it may lull health
authorities into thinking that the situation is not as bad as
feared, and may thus ignore the need for a public health
approach. On the other hand, the delay provides time to set
up screening services and organize the public health approach,
the better to prevent the onslaught of sight threatening
retinopathy and to make use of the calm before the storm.
The World Health Organization and all major professional
societies in ophthalmology and diabetology recognize that reg-
ular eye screening and preventive laser treatment are essential
to prevent the diabetes epidemic from becoming an enormous
world-wide epidemic of blindness. The WHO recommends that
every diabetic patient be screened for diabetic retinopathy once
a year, and those diagnosed with sight threatening retinopathy
receive the appropriate treatment. This recommendation is
based, in part, on the experience and success of the Nordic
countries, where 30 years of experience has proved the value
of this approach. The success of retinal screening for diabetic
eye disease is proved by experience, and amply reported in
the medical literature [5,13].
Historically, diabetic eye screening started as annual screen-
ing examinations and this has proved to be adequate for the
successful prevention of blindness. However, this ‘‘one size fits
all’’ approach is clearly simplistic
[20].
Diabetic patients are at variable risk for the development of
sight threatening retinopathy. This risk is influenced by the
duration and type of diabetes mellitus, blood glucose levels,
blood pressure, the presence of retinopathy and a few other
minor risk factors
[21,22]. These risk factors create a spectrum
of risk, with some individuals at high risk and many at low
risk, including those with a short duration of diabetes mellitus.
It would clearly make more sense to adjust the screening inter-
vals to the risk profile of the individual patient, so that those at
high risk frequently come for screening examinations and
those at low risk less frequently
[23].
We have developed a mathematical algorithm, which calcu-
lates the individual risk for sight threatening retinopathy based
on duration of diabetes, hemoglobin A1C levels, blood pres-
sure and presence of retinopathy and recommends an appro-
priate screening interval for each individual
[24]. This
algorithm is available on the internet on www.risk.is and was
tested in a database of diabetic screening for 20 years in
Denmark. With this algorithm, the number of screening visits
for the population could be reduced by more than 50%, whilst
maintaining safety. This is mostly due to less frequent screen-
ing visits for diabetic patients with short duration of diabetes,
as well as those in very good medical control. This use of infor-
mation technology means that for a given amount of medical
resources, twice the number of diabetic patients may be served,
compared with fixed annual examinations. In a country with a
rising diabetes epidemic and relatively many individuals with a
short duration of diabetes, the use of information technology
may be even more important and increase the efficacy of the
public health approach even more.
A public health approach and screening for diabetic
retinopathy is a proven method to dramatically reduce the dia-
betic blindness
[25–26]. This is the only way to prevent the
world-wide diabetes epidemic from becoming an epidemic of
blindness with enormous implications for health and the econ-
omy. Information technology makes screening more effective
and feasible on a global scale.
References
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2 Editorial
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J, Palsson O, Thorisdottir O, Einarsson S, Einarsdottir A,
Aspelund T. Information technology to control screening for
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2006;90:2–3
.
Einar Stefa
´
nsson
a,b,
*
Anna Bryndı
´
s Einarsdo
´
ttir
a
a
University of Iceland, Landspitali University Hospital,
Reykjavik, Iceland
b
King Saud University, Riyadh, Saudi Arabia
*
Corresponding author at: Acta Ophthalmologica,
University of Iceland, National University Hospital,
101 Reykjavı
´
k, Iceland.
Tel.: +354 543 7217 (O), +354 824 5962 (cell);
fax: +354 543 4831.
E-mail address:
einarste@landspitali.is (E. Stefa
´
nsson)
Editorial 3
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Geographically, the type 2 diabetes red zone is variable, ranging from dry desert areas to heavily raining green land. At the same time, it has the lowest level below sea and the highest mountains above sea level. This area is also unique for its wide cultural, social and ethnic variations. This makes the diabetes red zone area a positive research field for both the geographical and cultural impact of the disease. There is enough epidemiological data to support the fact that type 2 diabetes has a different presence in different populations that are reflected by the incidence of the disease and its prevalence. These could be attributed to different risk factors that affect any given population. Ethnicity, family history and ageing are unavoidable factors, all of which contribute to the high diabetes prevalence in certain populations [2]. Lifestyle change in both developed and developing countries, namely globalization, has had an effect on diabetes prevalence, which is associated with high calorie intake, low physical exercise and obesity. Further studies have confirmed the continuous increase in diabetes prevalence in every country, with a variable figure ranging between 1.4% in rural Vietnam [3] and 70% among Pima Indians in United States [4]. WHO studied the rising prevalence of diabetes mellitus and impaired glucose tolerance based on 75 communities in 32 countries [5] and it is time now for further studies that link the global diabetes database to the status of human health, and its burden on world economy. A population based surveys of the type 2 diabetes red zone would give the greatest chance to study the role of different risk factors that has been linked to the raising type 2 diabetes prevalence. There is enough scientific evidence to link urbanization to an increase of type 2 diabetes mellitus, regardless of the country’s financial status. There are many poor developing countries in this red zone that are affected by globalization and have demonstrated an increase in the incidence of this disease. This has been exacerbated by the new global increase of type 2 diabetes mellitus among children, as a result of the high prevalence of obesity and the change in lifestyle in the form of high calorie dietary intake and low physical activity in that age group [6]. The International Diabetes Federation (IDF) has produced a document listing the top 10 countries in terms of number of people with diabetes aged 20–79 years. This shows 5 out of 10 countries to be from the red zone, namely India, China, Japan, Pakistan and Egypt. These five countries contributed to 94.6% of the total number of people with diabetes among the top 10. It is anticipated that by 2025, Bangladesh will join the top 10 countries, replacing Japan. But when looking at the top 10 countries in terms of prevalence of diabetes, eight countries are located in the red zone area, namely Nauru, United Arab Emirates, Saudi Arabia, Bahrain, Kuwait, Oman, Tonga and Egypt. These countries will remain the top in year 2025. Table 1 shows the top 10 countries, according to the number of diabetic patients and the prevalence of diabetes, which compare data from the year 2007 with expected changes in the year 2025. Although India and China are inhabited by the largest number of diabetic patients (80.7 millions) as a result of their large population size, neither country appeared in the top 10 countries when diabetes prevalence was looked at. When looking to the highest prevalence of diabetes mellitus in the top 10 countries, six countries are from the Arab World (i.e., Middle East), but five of them are from the gulf countries, namely the United Arab Emirates, Saudi Arabia, Bahrain, Kuwait, and Oman. Gulf States have a higher prevalence rate than other Middle East countries such as Egypt. This observation provides a strong clue that Arab Ethnicity is at a higher risk of developing type 2 diabetes mellitus and that populations from Gulf States are the highest. It is anticipated that these countries will continue to be among the top 10 countries in the year 2025. Table 1. The top 10 countries for type 2 diabetes mellitus, according to the number and prevalence for people aged between 20 and 79 years in the year 2007 and 2025. 2007 2025 Patients (millions) Prevalence (%) Patients (millions) Prevalence (%) 1 India (40.9) Nauru (30.7) India (69.9) Nauru (32.3) 2 China (39.8) UAE (19.5) China (59.3) UAE (21.9) 3 USA (19.2) Saudi Arabia (16.7) USA (25.4) Saudi Arabia (18.4) 4 Russia (9.6) Bahrain (15.2) Brazil (17.6) Bahrain (17.0) 5 Germany (7.4) Kuwait (14.4) Pakistan (11.5) Kuwait (16.4) 6 Japan (7.0) Oman (13.1) Mexico (10.8) Tonga (15.2) 7 Pakistan (6.9) Tonga (12.9) Russia (10.3) Oman (14.7) 8 Brazil (6.9) Mauritius (11.1) Germany (8.1) Mauritius (13.4) 9 Mexico (6.1) Egypt (11.0) Egypt (7.6) Egypt (13.4) 10 Egypt (4.4) Mexico (10.6) Bangladesh (7.4) Mexico (12.4) Source: Diabetes Atlas Third Edition, International Diabetes Federation (IDF) – 2006. Table options The type 2 diabetes red zone could now be easily divided into two parts: the eastern part, which has the largest number of diabetic patients but with a prevalence rate of less than 10%; and the western part, which has the highest diabetes prevalence (more than 10%) but a smaller number of diabetic patients, due to their small population size. The western part consists of Middle Eastern countries, which are inhabited mainly by Arab Ethnicity. The Republic of Nauru, an Island in the South Pacific, has the highest global prevalence rate of type 2 diabetes, but is only inhabited by 12,000 people with different ethnicities, according to a United Nations estimation. There are numerous global studies that link ethnicity to type 2 diabetes susceptibility, regardless of environmental factors. Studies have proved that even with equal lifestyle changes, the prevalence of type 2 diabetes mellitus differs between people with different ethnicity, regardless of their geographical location. Jenum et al. have demonstrated the high prevalence of diabetes among South Asian women in Norway after adjustment for age, adiposity, physical activity and education that could be explained by ethnicity [7]. Asian Americans and Pacific Islanders have also been found to be significantly more at risk of developing type 2 diabetes than non-Hispanic whites [8]. These scientific clues may mean that the ethnicity of people from the red zone has a special effect on type 2 diabetes etiology. Tan et al. have shown the effect of ethnicity between Chinese, Malay and Indians in Singapore for type 2 diabetes, especially among females [9], which confirms the ethnicity effect within the red zone geographical location. Arabs who could be considered an ethnicity with high frequency for type 2 diabetes have demonstrated the high prevalence in the Middle East, and also as an immigrant to different parts of the world, as shown in different studies [10]. The red zone for type 2 diabetes relates to high prevalence or large population, and warrants more study and a better focus when fighting this disease and its complications globally. This area is also expected to have more than 50% of mortality and morbidity from this disease. Half of the global economic impact of type 2 diabetes is from this area. This geographical area thus needs more attention when considering prevention programs and drugs supply. References [1] US Consensus Bureau – World POPClock Projection. [2] J.P. Boyle, A.A. Honeycutt, K.M. Venkat Narayan, T.J. Hoerger, L.S. Geiss, H. Chen, et al. Projection of diabetes burden through 2050 Diab Care, 24 (2001), pp. 1936–1940 CrossRef | View Record in Scopus | Citing articles (673) [3] Ekoe Jean-Marie. The epidemiology of diabetes mellitus; 2001. [4] E.T. Lee, B.V. Howard, P.J. Savage, L.D. Cowan, R.R. Fabsitz, A.J. Oopik, et al. Diabetes mellitus and impaired glucose tolerance in three American Indian population aged 45–74 years: the strong heart study Diab Care, 18 (5) (1995), pp. 599–610 CrossRef | View Record in Scopus | Citing articles (156) [5] H. King, M. Rewers WHO ad hoc diabetes reporting group: global estimates for prevalence of diabetes and impaired glucose tolerance in adults Diab Care, 16 (1993), pp. 157–177 CrossRef | View Record in Scopus | Citing articles (781) [6] C.B. Ebbeling, D.B. Pawlak, D.S. Ludwig Childhood obesity: public-health crisis, common sense cure Lancet, 360 (9331) (2002), pp. 473–482 Article | PDF (170 K) | View Record in Scopus | Citing articles (1668) [7] A.K. Jenum, I. Holme, S. Graff-Iversen, K.I. Birkeland Ethnicity and sex are strong determinants of diabetes in an urban western society: implications for prevention Diabetologia, 48 (2005), pp. 435–439 CrossRef | View Record in Scopus | Citing articles (84) [8] Jen’nan Ghazal Read, Benjamin Amick, Katharine M. Donato Arab immigrants: a new case for ethnicity and health? Soc Sci Med, 61 (2005), pp. 77–82 Article | PDF (186 K) | View Record in Scopus | Citing articles (51) [9] C.E. Tan, S.C. Emmanuel, B.Y. Tan, E. Jacob Prevalence of diabetes and ethnic differences in cardiovascular risk factors Diab Care, 22 (2) (1999), pp. 241–247 CrossRef | View Record in Scopus | Citing articles (178) [10] L.A. Jaber, M.B. Brown, A. Hammad, S.N. Nowak, Q. Zhu, A. Ghafoor, et al. Epidemiology of diabetes among Arab Americans Diab Care, 26 (2) (2003), pp. 308–313 CrossRef | View Record in Scopus | Citing articles (78)
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