The burden of diabetes in India
India, the second most populous country of the world, has been severely affected by the global diabetes epidemic. As per the International Diabetes Federation (2013), approximately 50% of all people with diabetes live in just three countries: China (98.4 million), India (65.1 million) and the USA (24.4 million). There is clear evidence to show that diabetes prevalence is rapidly increasing, especially in urban India. The conventional risk factors of urbanization, unhealthy eating habits and physical inactivity, coupled with inherent genetic attributes and differences in body composition are propelling the increase in cases of diabetes. Accordingly, diabetes related complications are also on the rise and contribute significantly to overall morbidity and mortality. The low levels of education and poor awareness of the disease in the country are enhancing its impact on health of the population.
While communicable diseases are slowly getting controlled in low and middle income countries (LMIC), such as India, there is a significant increase in the burden of non communicable diseases, including but not restricted to diabetes. Going by the model of four phases of health transition, India is currently in the age of man-made and degenerative diseases. This age is characterised by a life expectancy close to 50-60 years and unhealthy lifestyles which promote diseases like cardiovascular disease and hypertension.
While comprehensive data are not available, smaller studies have been performed in various states of India to study the prevalence of diabetes. Based on these studies, the highest prevalence reported is from Ernakulum in Kerala (19.5%) and the lowest from Kashmir valley (6.1%). Most other areas have prevalence above 10%.
While most prevalence studies in India have been regional, there has been a recent effort supported by the Indian Council of Medical Research to estimate the nationwide prevalence of diabetes (urban and rural) . The first phase of the ICMR-INDIAB study (involving 3 states and one Union Territory) has been completed. In this study around 13000 subjects were studied using a stratified multistage sampling design. The rural and urban population were equally represented. The prevalence rates of diabetes and prediabetes were assessed by measurement of fasting and 2 hour post glucose load capillary blood glucose. This study projects a likely national estimate of 62.4 million patients with diabetes and 77.2 million with prediabetes. Prevalence of diabetes was reported ranging from 5.3% to 13.6% in different areas in this study .
There is limited information on the incidence of diabetes in India. One such data source is the New Delhi Birth Cohort study, which reported an annual incidence of 1.0% for males and 0.5 % for females, even though this population was in the 4th decade of life . In a longitudinal cohort from Chennai, the incidence of diabetes was calculated as 20.2 per 1000 person years among subjects with prior normal glucose tolerance, and 64.8 per 1000 person years in those with prediabetes .
Urban- rural differences
While the increase in prevalence is occurring in rural as well as urban areas, the urban areas demonstrate a faster increase. However disturbingly, in recent time an acceleration has been noted in rural areas which probably represents the adoption of unhealthy lifestyles in rural population (Table 1).
The International Diabetes Federation (IDF) Diabetes Atlas states that in low and middle income countries, the number of people with diabetes in urban areas is 181 million, while 122 million live in rural areas .The data from the ICMR INDIAB study also shows that prevalence of diabetes in urban areas ranged from 10.9 to 14.2% while in rural areas the range was 3.0 to 8.3%. A rural-urban gradient has also been observed in a study from Tamil Nadu, where the prevalence of diabetes in peri-urban villages and cities in the state of Tamil Nadu reported as 9.2% and 16.4% respectively.
In the urban areas, the increase in prevalence of diabetes is evident from findings of periodic population based studies performed in the city of Chennai in South India in last 2 decades. In these studies, the prevalence of diabetes increased from 8.3% in 1989 to 18.6 in 2006. Similar observations have been reported from Delhi, North India, wherein the urban prevalence of diabetes in studies conducted two decades apart (1991-1994 to 2010-2012) increased from 14.2% to 23.0%. Also, the age at detection of diabetes had decreased over this period, with urban metropolitan data suggesting nearly 5% diabetes prevalence in the age group 25-34 years .
While rural areas have a lower prevalence of diabetes, there are variations in prevalence by region. In studies from Rajasthan, Vellore and Mysore, prevalence in rural areas has been reported to be as low as 1.8 %, 2.1% and 3.8% respectively. This contrasts with the extremely high prevalence of 19.8% reported from a rural hilly area in North Eastern India. A trend of increasing prevalence in rural areas is noticeable with several studies done in the past decade showing prevalence ranging from 9.2-13.3 %. The rural areas of economically backward states have a lower prevalence as reported in the ICMR-INDIAB study. The prevalence in rural areas of the economically better regions of Chandigarh, Tamil Nadu and Maharashtra was 8.3%,7.8% and 6.5% respectively. On the other hand, in the economically less advantaged state of Jharkhand, the prevalence was only 3.0% .
Indians seem to be at higher risk for diabetes. Apart from the conventional risk factors propelled by urbanization, industrialization, globalization and aging, other factors may also contribute. It has been proposed that obesity, regional adiposity, higher percentage body fat, early life influences including foetal programming and genetic factors contribute to increased risk. The variables independently associated with diabetes in adults include age, BMI, WHR, income and family history of diabetes. Indians tend to have more body fat and a higher risk of diabetes for the same BMI as compared to Western populations. In view of this, the WHO recommends that for public health action, BMI of 23–27.5 kg/m2 be considered at increased risk for type 2 diabetes and cardiovascular disease; and 27.5 kg/m2 or higher be considered as high risk. An increase in obesity prevalence is apparent from the National Family Health Survey (NFHS) data, wherein the percentage of women aged 15-49 years who were overweight or obese , increased from 11% in NFHS- 2 (1998-1999) to 15% in NFHS-3 (2005-2006).
Similarly, body fat percentage (greater than 25% in males and 30% in females), waist circumference (more than 80 cm in females and 90 cm in males) and increased waist: height ratio (≥0.58), is associated with increased risk of diabetes in Indian population.
Urban migration has been linked with increasing prevalence of diabetes. As compared to rural population , urban migrants have higher weight, body mass index (BMI), waist hip ratio (WHR), systolic blood pressure (SBP), cholesterol, HOMA-IR , fat intake while physical activity is less.
Changing diets and declining physical activity levels, especially in urban India, have also contributed to the rising prevalence of obesity and diabetes. Consumption of traditional diets has declined in urban areas, with city-dwellers consuming up to 32% of daily energy requirement as fat. Increased automation, use of automobiles, and increasing "screen time" has limited physical activity, especially in urban India. While Indians share several high risk alleles for diabetes with Caucasians, a recent Genome Wide Association Study (GWAS), has reported a new susceptibility locus at 2q21. It is however clear that in a complex disorder such as diabetes, the known genetic loci contribute approximately 10% to the risk of disease development.
Though type 2 diabetes usually manifests clinically in adults, risk factors start getting established even in childhood. Obesity and overweight are emerging as important public health problems, with a reported prevalence between 20-30% in urban socio-economically advantaged school going children. Metabolic abnormalities, including dysglycaemia (about 10%) and dyslipidaemia (25-40%), has been reported in apparently healthy obese or overweight children. A comparison of studies over the last two decades reveals that there has been a significant increase in childhood obesity, with median weight being approximately 5 kg more in each age group. Obesity in school children is more prevalent in the upper socioeconomic sections of society (20-25% children being overweight or obese) compared to children hailing from the less affluent sections (2-4%).
Influences in early life, including the intra-uterine period, may also predispose to diabetes. In the New Delhi Birth Cohort, dysglycaemia in later life inversely related to BMI and weight at 1 year of age. After 2 years of age, increase in BMI was associated with increased risk of diabetes. The highest prevalence of diabetes and dysglycaemia was in subjects who were in the lowest third of the group with respect to BMI at 2 years and highest at age 12 years .Thus low birth weight and accelerated weight gain after 48 months are risk factors for adult glucose intolerance.
Co morbidities and complications
The data regarding complications of diabetes has been drawn mostly from small scale population based studies conducted mostly in urban areas in South India. In the Chennai Urban Rural Epidemiological Study, overall prevalence of diabetic retinopathy and macular edema was 17.6% and 5.2% respectively. In the same study , microalbuminuria was found in 26.9% and overt nephropathy in 2.2%.The prevalence of coronary artery disease and peripheral vascular disease has been reported as 21.4% and 3.2% respectively, while peripheral neuropathy is seen in 26.10 % subjects. The prevalence of carotid atherosclerosis was reported as 20%. Among recently diagnosed type 2 diabetics , 13.5 had neuropathy while retinopathy and nephropathy were present in 6% and 1% respectively.
In more than 20,000 Indians with type 2 diabetes who participated in the A1chieve study, the prevalence of various complications was as follows: neuropathy (24.6%), cardiovascular (23.6%), renal (21.1%), eye (16.6%) and foot ulcer (5.1%). In the improving management practices and clinical outcomes in type 2 diabetes (IMPACT) study, out of 20,000 Indian patients with type 2 diabetes mellitus , 60% had coronary artery disease (CAD), 30 % had peripheral arterial disease, while neuropathy and retinopathy were present in 65.1 % and 38.3% subjects respectively.
Issues related to awareness
There is poor awareness about diabetes in the Indian population. 25% of an urban population was unaware of a medical condition called DM, Similarly, only 22% of the general population and 41% of known diabetics felt that diabetes could be prevented. Only 12% were aware of the risk factors for diabetes. Even among people with diabetes, only 40% were aware that it could result in organ damage.
In the ICMR INDIAB study 43.2% subjects were aware of a condition called diabetes. Overall, urban residents had higher awareness rates (58.4%) compared to rural residents (36.8%). 56.3 % of the population knew that diabetes can be prevented and 51.5% understood that diabetes can affect other organs.
In line with poor awareness, glycaemic control in Indian patients is also poor. In the ICMR-INDIAB study approximately 30 % subjects had glycosylated haemoglobin (HbA1C) levels below 7%. Only 22.4% of urban and 15.4% of rural subjects had reported having checked their HbA1c in the past year. Thus, there is a rapid increase in diabetes prevalence across the country, predominantly in urban areas, but with rural areas in some parts of India also reporting nearly 10% prevalence. Industrialization, urbanization, decline in traditional cultural practices, physical inactivity, obesity (general and central), early life influences, genetics are major risk factors contributing to this increase in prevalence. There is a need to address issues of awareness, education, evidence based clinical care and policy in the country.
Table 1. Studies showing prevalence of diabetes in India (urban and rural)
|Year||Author||Place||Prevalence (%) Urban||Prevalence (%) Rural|
|1971||Tripathy et al||Cuttack||1.2|
|1972||Ahuja et al||New Delhi||2.3|
|1979||Gupta et al||Multicentre||3.0||1.3|
|1984||Murthy et al||Tenali||4.7|
|1988||Ramachandran et al||Kudremukh||5.0|
|1989||Kodali et al||Gangavathi||2.2|
|1989||Rao et al||Eluru||1.6|
|1991||Ahuja et al||New Delhi||6.7|
|1992||Ramachandran et al||Madras||8.2||2.4|
|1997||Ramachandran et al||Madras||11.6|
|2001||Ramachandran et al||6 metros||12.1|
|2001||Misra et al||Delhi||11.2|
|2001||Mohan et al||Chennai||12.1|
|2001||Sadikot et al||PODIS 5.6||2.7|
|2003||Gupta et al||Jaipur||8.6|
|2004||Agarwal et al||Rajasthan||1.8|
|2004||Ramachandran et al||Chennai||6.4|
|2004||Mohan et al||Chennai||14.3|
|2005||Basavanagowdappa et al||Mysore||3.8|
|2005||Prabhakaran et al||Delhi||15.0|
|2006||Reddy et al al||National||10.1|
|2006||Deo et al||Maharashtra||9.3|
|2006||Menon et al||Eranakulam||19.5|
|2006||Chow et al||Andhra||13.2|
|2007||Raghupathy et al||Vellore||3.7||2.1|
|2008||Mohan et al||Nation-wide; self reported||7.3||3.1|
|2008||Ramachandran et al||Tamil Nadu||18.6||9.2|
|2011||ICMR INDIAB (Anjana et al)||Chandigarh||14.2||8.3|
|2011||ICMR INDIAB (Anjana et al)||Tamil Nadu||13.7||7.8|
|2011||ICMR INDIAB (Anjana et al)||Maharashtra||10.9||6.5|
|2011||ICMR INDIAB (Anjana et al)||Jharkhand||13.5||3.0|
|2012||Prasad et al||Orissa||15.7|
|2012||Rajput et al||Haryana||13.3|
|2012||Singh et al||Delhi (age >60 urban slum)||18.0|
|2013||Shah et al||Manipur (Muslims only)||16.6|
|2013||Kumar et al||West Bengal(Police men)||15.0|
|2014||Walia et al||Chandigarh||16.4|
|2014||Zaman et al||Arunachal Pradesh||19. 8|
^ IDF Diabetes Atlas . 6 th edition
^ Anjana RM et al.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 Research-INdia DIABetes (ICMR-INDIAB) study. Diabetologia. 2011 Dec;54(12):3022-7. doi: 10.1007/s00125-011-2291-5. Epub 2011 Sep 30.
^ Huffman MD et al. Incidence of cardiovascular risk factors in an Indian urban cohort results from the New Delhibirth cohort. J Am Coll Cardiol. 2011 Apr 26;57(17):1765-74. doi: 10.1016/j.jacc.2010.09.083.
^ Mohan V et al. Incidence of diabetes and pre-diabetes in a selected urban south Indian population (CUPS-19). J Assoc Physicians India. 2008 Mar;56:152-7.
^ Mohan V et al. Secular trends in the prevalence of diabetes and impaired glucose tolerance in urban South India--the Chennai Urban Rural Epidemiology Study (CURES-17). Diabetologia. 2006 Jun;49(6):1175-8. Epub 2006 Mar 29.
^ WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet. 2004 Jan 10;363(9403):157-63.