Diabetes in the tropics: prevalent, increasing and a major public health problem Ranjit Unnikrishnan and Viswanathan Mohan* Madras Diabetes Research Foundation & Dr. Mohan’s Diabetes Specialities Centre, WHO Collaborating Centre for Non-communicable Diseases Prevention and Control, 4 Conran Smith Road, Gopalapuram, Chennai, India *Corresponding author: Tel: +91 44 4396 8888; Fax: +91 44 2835 0935; E-mail: [email protected] Received 11 March 2016; accepted 14 March 2016 Keywords: Diabetes, Epidemiologic transition, Tropics
Diabetes mellitus is no longer confined to the developed nations of the temperate zone, but has attained epidemic proportions in the developing nations of the tropics as well. The latter group of nations’ unique challenges include low rates of disease detection and limited access to preventive and therapeutic measures. Lessons learned from the experiences of the developed world need to be appropriately adapted and applied to these populations in order to prevent the spread of the diabetes epidemic in a cost-effective manner in developing countries of the world where 80% of all people with diabetes currently live. Tropical regions of the world, comprising large parts of Asia and most of Africa and Latin America, harbor a larger population with diabetes mellitus than any other region of the world.1 Even so, diabetes is not often considered when enumerating the major ‘tropical’ diseases. The chronic and insidious nature of the disease, and the misplaced (yet widespread) belief that the disease is a preserve of the prosperous temperate zone, underlie this misconception. In 1967, Dodu2 assumed diabetes prevalence rates of 0.1 to 2% among the general adult population in most tropical countries, at a time when the rates in developed nations were nearly thrice as high. A glance at the latest statistics released by the International Diabetes Federation1 will reveal that the prevalence rates in the tropics now rival or even surpass those of the developed western nations in the temperate regions. The Indian subcontinent, China and the Pacific Islands have been hardest hit by the epidemic of diabetes. China has more than 100 million people with diabetes and India nearly 70 million. Out of the ten countries harboring the most people with diabetes, six are in the tropics; of the ten countries with the highest prevalence of diabetes in the world, seven are Pacific Island nations and the remaining three are located in the
Middle East. All in all, more than 75% of the world’s population with diabetes resides in low- and middle-income nations, almost exclusively located in the tropics and sub-tropics. It has long been recognized that there are considerable differences between diabetes in the tropics and diabetes in the rest of the world. Indeed, a workshop was conducted in 1995 to stimulate further research into types of diabetes specific to tropical regions of the world.3 At this workshop, special emphasis was made to diabetes associated with malnutrition (malnutrition modulated diabetes mellitus) and diabetes secondary to tropical pancreatitis (fibrocalculous pancreatic diabetes). Less attention was paid to type 2 diabetes (then termed non-insulin dependent diabetes mellitus) occurring in the tropics, but it is this type of diabetes that is the most common in these regions today as is the case in the rest of the world. Much of the research on ‘tropical’ type 2 diabetes has been carried out in India. Type 2 diabetes in Asian Indians, be they resident in India or part of the widespread diaspora in the US, Europe, Middle East, South Africa or the Caribbean, presents certain distinctive features,4 such as development of the disease at younger ages and at lower levels of obesity compared to white Caucasians. The prevalence of undiagnosed diabetes is also high, with nearly three out of four individuals in certain parts of rural India with diabetes being unaware of their condition.5 Development of diabetes at younger ages implies that many of these individuals will suffer morbidity due to diabetes complications during the prime of their productive lives, which can have serious societal and economic consequences. Developing countries face additional problems in their efforts against diabetes, including poor levels of awareness of disease among the population,6 unavailability of modern diagnostic and therapeutic modalities and trained healthcare personnel, and consequent poor control of diabetes.7
© The Author 2016. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: [email protected]
263
EDITORIAL
Trans R Soc Trop Med Hyg 2016; 110: 263–264 doi:10.1093/trstmh/trw021
R. Unnikrishnan and V. Mohan
India also represents a classic example of the epidemiologic transition facing many countries in the tropics. Improvements in the public health system and widespread immunization programs have minimized, but not completely eliminated, the threat of infectious disease epidemics. Improved life expectancy, a welcome dividend of this achievement, has had some unexpected and unwanted consequences in the emergence of lifestyle diseases like diabetes. The presence of this dual burden of disease places policymakers in an unenviable position: they need to devote sufficient resources to the management and prevention of non-communicable diseases while, at the same time, ensuring that the hard-won gains in the battle against infectious disease are not frittered away. Several other countries such as China, Brazil, Pakistan and Bangladesh in the tropics also face this dilemma, while others countries, such as those in Sub-Saharan Africa, are further behind in the epidemiological transition wherein infectious diseases still hold sway. However, it is only a matter of time before they, too, will have to prepare to combat the rising tide of diabetes and other non-communicable diseases. Epidemiological transitions occur not only in nations as a whole, but also in population subgroups within nations. In developed nations today, diabetes is chiefly a disease of the underprivileged (such as ethnic and racial minority groups), who tend to neither be aware of the benefits of, nor have access to, healthy eating and lifestyle patterns.8 In contrast, diabetes in developing countries tends to affect the more prosperous sections of society, who have regular access to high-calorie foodstuffs and mechanized means of transport, and who are usually employed in physically undemanding occupations. However, it is worrying to note that prevalence rates of diabetes have, at least in India, started to go up even among the low- and middleclass.9 Improved social mobility, reliable supply of refined food grains (ironically, supplied through the government-funded public distribution system) and mechanization of even the most menial of occupations has transformed the lifestyle of the poorer sections of society. However, this has not been accompanied by increased awareness of healthier lifestyle patterns; more importantly, perhaps, healthy food options and facilities for recreational physical activity remain sadly out of reach for most people in these countries. Thus, as the more prosperous sections of society increasingly become aware of the consequences of their unhealthy lifestyles and adopt preventive steps, the prevalence of diabetes is likely to decline in them; the poorer sections of society, exposed to cheap, high-calorie foodstuffs with no opportunity to burn off these calories, will increasingly fall prey to diabetes and other lifestyle diseases, the treatment of which they can ill-afford. Fortunately, there is now sufficient evidence to show that diabetes can be prevented (or at least delayed) in populations at risk by promotion of healthy behaviors such as dietary modification and regular physical activity.10 The challenge facing developing regions of the tropical world is to adapt the lessons
264
learned from these landmark studies and apply them to their populations in the most appropriate and cost-effective way. The consequences of allowing the epidemic of diabetes to progress in the vast numbers of individuals at risk undoubtedly justify the time and expense likely to be incurred in these efforts. The time to act is now!
Authors’ contributions: RU and VM drafted the manuscript and critically revised the paper for intellectual content. Both authors read and approved the final manuscript. VM is guarantor of the paper. Funding: None. Competing interests: None. Ethical approval: Not required.
References 1 International Diabetes Federation. Diabetes Atlas Seventh Edition 2015. Brussels, Belgium: IDF; 2015. http://www.diabetesatlas.org [accessed 10 December 2015]. 2 Dodu SR. Diabetes in the tropics. Br Med J 1967;2:747–50. 3 Hoet JJ, Tripathy BB. Report of the International Workshop on types of diabetes peculiar to the tropics. Diabetes Care 1996;19:1014. 4 Unnikrishnan R, Anjana RM, Mohan V. Diabetes in South Asians: is the phenotype different? Diabetes 2014;63:53–5. 5 Anjana RM, Pradeepa R, Deepa M et al. ICMR–INDIAB Collaborative Study Group. Prevalence of diabetes and prediabetes (impaired fasting glucose and/or impaired glucose tolerance) in urban and rural India: Phase I results of the Indian Council of Medical ResearchINdia DIABetes (ICMR-INDIAB) study. Diabetologia 2011;54:3022–7. 6 Deepa M, Bhansali A, Anjana RM et al. Knowledge and awareness of diabetes in urban and rural India: The Indian Council of Medical Research India Diabetes Study (Phase I): Indian Council of Medical Research India Diabetes (ICMR-INDIAB)-4. Indian J Endocrinol Metab 2014;18:379–85. 7 Unnikrishnan R, Anjana RM, Deepa M et al. Glycemic control among individuals with self-reported diabetes in India–the ICMR-INDIAB Study. Diabetes Technol Ther 2014;16:596–603. 8 Beckles GL, Chou GF. Centers for Disease Control and Prevention (CDC). Diabetes - United States, 2006 and 2010. MMWR Suppl 2013;62:99–104. 9 Deepa M, Anjana RM, Manjula D et al. Convergence of prevalence rates of diabetes and cardiometabolic risk factors in middle and low income groups in urban India: 10-year follow-up of the Chennai Urban Population Study. J Diabetes Sci Technol 2011;5:918–27. 10 American Diabetes Association and National Institute of Diabetes and Digestive and Kidney Diseases. Prevention or delay of type 2 diabetes. Diabetes Care 2004;27(Suppl 1):S47.
Diabetes mellitus is no longer confined to the developed nations of the temperate zone, but has attained epidemic proportions in the developing nations of the tropics as well. The latter group of nations’ unique challenges include low rates of disease detection and limited access to preventive and therapeutic measures. Lessons learned from the experiences of the developed world need to be appropriately adapted and applied to these populations in order to prevent the spread of the diabetes epidemic in a cost-effective manner in developing countries of the world where 80% of all people with diabetes currently live. Tropical regions of the world, comprising large parts of Asia and most of Africa and Latin America, harbor a larger population with diabetes mellitus than any other region of the world.1 Even so, diabetes is not often considered when enumerating the major ‘tropical’ diseases. The chronic and insidious nature of the disease, and the misplaced (yet widespread) belief that the disease is a preserve of the prosperous temperate zone, underlie this misconception. In 1967, Dodu2 assumed diabetes prevalence rates of 0.1 to 2% among the general adult population in most tropical countries, at a time when the rates in developed nations were nearly thrice as high. A glance at the latest statistics released by the International Diabetes Federation1 will reveal that the prevalence rates in the tropics now rival or even surpass those of the developed western nations in the temperate regions. The Indian subcontinent, China and the Pacific Islands have been hardest hit by the epidemic of diabetes. China has more than 100 million people with diabetes and India nearly 70 million. Out of the ten countries harboring the most people with diabetes, six are in the tropics; of the ten countries with the highest prevalence of diabetes in the world, seven are Pacific Island nations and the remaining three are located in the
Middle East. All in all, more than 75% of the world’s population with diabetes resides in low- and middle-income nations, almost exclusively located in the tropics and sub-tropics. It has long been recognized that there are considerable differences between diabetes in the tropics and diabetes in the rest of the world. Indeed, a workshop was conducted in 1995 to stimulate further research into types of diabetes specific to tropical regions of the world.3 At this workshop, special emphasis was made to diabetes associated with malnutrition (malnutrition modulated diabetes mellitus) and diabetes secondary to tropical pancreatitis (fibrocalculous pancreatic diabetes). Less attention was paid to type 2 diabetes (then termed non-insulin dependent diabetes mellitus) occurring in the tropics, but it is this type of diabetes that is the most common in these regions today as is the case in the rest of the world. Much of the research on ‘tropical’ type 2 diabetes has been carried out in India. Type 2 diabetes in Asian Indians, be they resident in India or part of the widespread diaspora in the US, Europe, Middle East, South Africa or the Caribbean, presents certain distinctive features,4 such as development of the disease at younger ages and at lower levels of obesity compared to white Caucasians. The prevalence of undiagnosed diabetes is also high, with nearly three out of four individuals in certain parts of rural India with diabetes being unaware of their condition.5 Development of diabetes at younger ages implies that many of these individuals will suffer morbidity due to diabetes complications during the prime of their productive lives, which can have serious societal and economic consequences. Developing countries face additional problems in their efforts against diabetes, including poor levels of awareness of disease among the population,6 unavailability of modern diagnostic and therapeutic modalities and trained healthcare personnel, and consequent poor control of diabetes.7
© The Author 2016. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: [email protected]
263
EDITORIAL
Trans R Soc Trop Med Hyg 2016; 110: 263–264 doi:10.1093/trstmh/trw021
R. Unnikrishnan and V. Mohan
India also represents a classic example of the epidemiologic transition facing many countries in the tropics. Improvements in the public health system and widespread immunization programs have minimized, but not completely eliminated, the threat of infectious disease epidemics. Improved life expectancy, a welcome dividend of this achievement, has had some unexpected and unwanted consequences in the emergence of lifestyle diseases like diabetes. The presence of this dual burden of disease places policymakers in an unenviable position: they need to devote sufficient resources to the management and prevention of non-communicable diseases while, at the same time, ensuring that the hard-won gains in the battle against infectious disease are not frittered away. Several other countries such as China, Brazil, Pakistan and Bangladesh in the tropics also face this dilemma, while others countries, such as those in Sub-Saharan Africa, are further behind in the epidemiological transition wherein infectious diseases still hold sway. However, it is only a matter of time before they, too, will have to prepare to combat the rising tide of diabetes and other non-communicable diseases. Epidemiological transitions occur not only in nations as a whole, but also in population subgroups within nations. In developed nations today, diabetes is chiefly a disease of the underprivileged (such as ethnic and racial minority groups), who tend to neither be aware of the benefits of, nor have access to, healthy eating and lifestyle patterns.8 In contrast, diabetes in developing countries tends to affect the more prosperous sections of society, who have regular access to high-calorie foodstuffs and mechanized means of transport, and who are usually employed in physically undemanding occupations. However, it is worrying to note that prevalence rates of diabetes have, at least in India, started to go up even among the low- and middleclass.9 Improved social mobility, reliable supply of refined food grains (ironically, supplied through the government-funded public distribution system) and mechanization of even the most menial of occupations has transformed the lifestyle of the poorer sections of society. However, this has not been accompanied by increased awareness of healthier lifestyle patterns; more importantly, perhaps, healthy food options and facilities for recreational physical activity remain sadly out of reach for most people in these countries. Thus, as the more prosperous sections of society increasingly become aware of the consequences of their unhealthy lifestyles and adopt preventive steps, the prevalence of diabetes is likely to decline in them; the poorer sections of society, exposed to cheap, high-calorie foodstuffs with no opportunity to burn off these calories, will increasingly fall prey to diabetes and other lifestyle diseases, the treatment of which they can ill-afford. Fortunately, there is now sufficient evidence to show that diabetes can be prevented (or at least delayed) in populations at risk by promotion of healthy behaviors such as dietary modification and regular physical activity.10 The challenge facing developing regions of the tropical world is to adapt the lessons
264
learned from these landmark studies and apply them to their populations in the most appropriate and cost-effective way. The consequences of allowing the epidemic of diabetes to progress in the vast numbers of individuals at risk undoubtedly justify the time and expense likely to be incurred in these efforts. The time to act is now!
Authors’ contributions: RU and VM drafted the manuscript and critically revised the paper for intellectual content. Both authors read and approved the final manuscript. VM is guarantor of the paper. Funding: None. Competing interests: None. Ethical approval: Not required.
References 1 International Diabetes Federation. Diabetes Atlas Seventh Edition 2015. Brussels, Belgium: IDF; 2015. http://www.diabetesatlas.org [accessed 10 December 2015]. 2 Dodu SR. Diabetes in the tropics. Br Med J 1967;2:747–50. 3 Hoet JJ, Tripathy BB. Report of the International Workshop on types of diabetes peculiar to the tropics. Diabetes Care 1996;19:1014. 4 Unnikrishnan R, Anjana RM, Mohan V. Diabetes in South Asians: is the phenotype different? Diabetes 2014;63:53–5. 5 Anjana RM, Pradeepa R, Deepa M et al. ICMR–INDIAB Collaborative Study Group. Prevalence of diabetes and prediabetes (impaired fasting glucose and/or impaired glucose tolerance) in urban and rural India: Phase I results of the Indian Council of Medical ResearchINdia DIABetes (ICMR-INDIAB) study. Diabetologia 2011;54:3022–7. 6 Deepa M, Bhansali A, Anjana RM et al. Knowledge and awareness of diabetes in urban and rural India: The Indian Council of Medical Research India Diabetes Study (Phase I): Indian Council of Medical Research India Diabetes (ICMR-INDIAB)-4. Indian J Endocrinol Metab 2014;18:379–85. 7 Unnikrishnan R, Anjana RM, Deepa M et al. Glycemic control among individuals with self-reported diabetes in India–the ICMR-INDIAB Study. Diabetes Technol Ther 2014;16:596–603. 8 Beckles GL, Chou GF. Centers for Disease Control and Prevention (CDC). Diabetes - United States, 2006 and 2010. MMWR Suppl 2013;62:99–104. 9 Deepa M, Anjana RM, Manjula D et al. Convergence of prevalence rates of diabetes and cardiometabolic risk factors in middle and low income groups in urban India: 10-year follow-up of the Chennai Urban Population Study. J Diabetes Sci Technol 2011;5:918–27. 10 American Diabetes Association and National Institute of Diabetes and Digestive and Kidney Diseases. Prevention or delay of type 2 diabetes. Diabetes Care 2004;27(Suppl 1):S47.
