AAYYUSKAAM: INDIAN TYPE II DIABETES

“INDIAN TYPE II DIABETES”

Current Status:

India leads the world with largest number of diabetic subjects; the “diabetes capital of the world”. WHO reports show that 32 million people had diabetes in the year 2000. The International Diabetes Federation (IDF) estimates the total number of diabetic subjects to be around 40.9 million in India and this is further set to rise to 69.9 million by the year 2025 unless urgent preventive steps are taken.

To understand the status and pattern of type 2 diabetes in India various studies have been conducted on state and national level. Based on these studies various hypothesis and facts are reported. This data helps us to understand the depth of this epidemic in a broad and better perspective. Also, it shows us the way to identify the high risk individual and further management required to prevent further progression of diabetes.

Following are the abstracts of various studies conducted in India over the years and their results:

1. Prevalence rate in various part of India,

2. Prevalence rate of known cases,

3. Prevalence rate of undiagnosed cases & why they are more important – medically/nationally,

4. Prevalence rate of Pre-diabetics,

5. Prevalence rate of complications in diabetic & non-diabetic patient,

6. Asian Indian Phenotype,

7. The epidemiological transition

8. Indian Diabetes Risk Score (IDRS).

9. Prevention guide-line.

Major Studies Conducted in India: using WHO Diagnosis Criteria (50 g glucose load and capillary blood glucose level >170 mg/dl)

The Indian Council Medical Research (ICMR, New Delhi). Screening was done in about 35,000 individuals above 14 yr of age, the prevalence was 2.1per cent in urban population and 1.5 per cent in the rural population while in those above 40 yr of age, the prevalence was 5 per cent in urban and 2.8 per cent in rural areas.

The National Urban Diabetes Survey (NUDS), a population based study was conducted in six metropolitan cities across India and recruited 11,216 subjects aged 20 yr and above representative of all socio-economic strata. The study reported that the age standardized prevalence of type 2 diabetes was 12.1 per cent. Also, the prevalence in the southern part of India to be higher-13.5 per cent in Chennai, 12.4 per cent, in Bangalore, and 16.6 per cent Hyderabad; compared to eastern India (Kolkatta), 11.7 per cent; northern India (New Delhi), 11.6 per cent; and western India (Mumbai), 9.3 per cent. The study also suggested that there was a large pool of subjects with impaired glucose tolerance (IGT), 14 per cent with a high risk of conversion to diabetes.

Chennai Urban Rural Epidemiology Study (CURES), was conducted on a representative population of Chennai. This study gave a unique opportunity to compare prevalence rates of diabetes in Chennai city over the past two decades. From 1989 to 1995, the prevalence of diabetes in Chennai increased by 39.8 per cent (8.3 to 11.6%); between 1995 to 2000 by 16.3 per cent (11.6 to 13.5%) and between 2000 to 2004, by 6.0 per cent (13.5 to 14.3%). Thus within a span of 14 yr, the prevalence of diabetes increased significantly by 72.3 per cent.

The Prevalence of Diabetes in India Study (PODIS): An urban-Rural difference in Diabetes Prevalence has been consistently reported from India. While the ICMR study reported that the prevalence was 2.1 per cent in urban and 1.5 per cent in rural areas, a later study showed that the prevalence was three times higher among the urban (8.2). A study done in Kerala the prevalence of diabetes was the highest in the urban (12.4%) areas, followed by the midland (8.1%), highland (5.8%) and coastal division (2.5%). PODIS: was carried out in 108 centers (49 urban and 59 rural) to look at the differences, which was 5.6% in the urban compared to the 2.7% in the rural population.

Undiagnosed Cases of Diabetes. Various studies have shown an increase in prevalence of known diabetes, but also reported a very high prevalence of undiagnosed diabetes in the community. While in CURES, the prevalence of known diabetes was 6.1 per cent that of undiagnosed diabetes was 9.1 per cent. Similarly, in the ADEPS, the prevalence of known and undiagnosed diabetes was 9.0 and 10.5 per cent respectively. The Kashmir valley study showed that the prevalence of undiagnosed diabetes was 4.25 per cent, which was more than double to that of the known diabetes (1.9%).

The individuals who are unaware of their disease status are left untreated and are thus more prone to micro vascular as well as macro vascular complications. Hence, it is necessary to detect the large pool of undiagnosed diabetic subjects in India and offer early therapy to these individuals, as they are more prone to land up in medical facilities after advanced pathological changes are developed, thus becoming difficult cases to be cured.

STATE	STUDY	YEAR	PRVALENCE OF KNOWN DIABETES (URBAN)	AGE GROUP(Yr)
Delhi	ICMR	1972	2.1%	14 - 40
	ICMR	1972	5.0%	+40
	NUDS	2001	11.6%	+20
	-	2001	10.3%	+40
Chennai	CURES	1988	8.2%	+40
	CURES	1995	11.6	+40
	CURES	2000	13.5	+40
	NUDS	2001	13.5%	+20
	CURES	2006	14.3%	+40
Kerala	-	1999	16.3%	+40
	ADEPS	2006	19.5%	+40
Guwahati	-	1999	8.2%	+40
Kashmir	-	2000	1.9%	+40
Banglore	NUDS	2001	12.4%	+20
Hyderabad	NUDS	2001	16.6%	+20
Kolkata	NUDS	2001	11.7%	+20
Mumbai	NUDS	2001	9.3%	+20
Jaipur	-	2003	8.6%	+40

*ICMR: Indian Council Medical Research, New Delhi

*NUDS: National Urban Diabetes Survey

*ADEPS: Amrita Diabetes and Endocrine Population Survey

*CURES: Chennai Urban Rural Epidemiology Study

Pre-diabetes: Impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) collectively called as pre-diabetic states, which have a high risk of conversion to diabetes. Several studies have shown that these pre-diabetic states are also high risk stages for cardiovascular disease. Hence data on IGT and IFG are also urgently needed as they are indicators of future diabetes prevalence and burden on the nation. The NUDS indicate the prevalence of IGT was higher than that of type 2 diabetes in four out of six cities studied. The prevalence of IGT was 16.8 per cent in Chennai, 14.9 per cent in Bangalore, 29.8 per cent in Hyderabad, 10 per cent in Kolkata, 10.8 per cent in Mumbai and 8.6 per cent in New Delhi. The ADEPS done in Kerala showed that 11.2 per cent of the subjects had either IFG or IGT.

A recent study has reported a decreased prevalence of IGT in an urban population compared to earlier studies done in the same city (16.8% in 2000 to 10.2% in 2004). This could suggest that the diabetes epidemic in urban India may be slowing down or it may also suggest that there could be a rapid progression from the normal state through IGT to diabetes, which could imply a rapid increase in the diabetes epidemic or a worsening diabetogenic environment.

Complications in India: Both macro vascular and micro vascular complications cause significant morbidity and mortality among diabetic subjects. The Chennai Urban Population Study (CUPS) and CURES provided valuable data from India. The prevalence of coronary artery disease (CAD) was 21.4 per cent among diabetic subjects compared to 9.1 per cent in subjects with normal glucose tolerance. The prevalence of CAD in IGT subjects were 14.9 per cent. It was also seen that the diabetic subjects had increased subclinical atherosclerosis as measured by intimal medial thickness (IMT) at every age point compared to subjects with normal glucose tolerance. A recent study showed that carotid intima medial thickness increased with worsening grades of glucose tolerance. The prevalence of peripheral vascular disease (PVD) was 6.3 per cent among diabetic subjects compared to 2.7 per cent in non-diabetic subjects. The CURES Eye study is the largest population based data on the prevalence of diabetic retinopathy done in India. This study showed that the overall prevalence was 17.6 per cent. A recent population based study reported that the prevalence of overt nephropathy was 2.2 per cent in Indians while micro-albuminuria was present in 26.9 per cent. Glycated hemoglobin, duration of diabetes and systolic blood pressure were independently associated with diabetic nephropathy.

Overall, Asian Indians appear to have a greater predilection for cardiovascular complications. A recent follow up of the original CUPS cohort showed that the overall mortality rates were nearly three-fold higher (18.9 per 1000 person-years) in people with diabetes compared to non diabetic subjects (5.3 per 1000 person-years). The Hazard ratio (HR) for all cause mortality for diabetes was found to be 3.6 compared to non diabetic subjects. The study also showed that mortality due to cardiovascular (diabetic subjects: 52.9% vs. non diabetic subjects 24.2%) and renal (diabetic subjects 23.5% vs. non diabetic subjects 6.1%) causes was higher among diabetic subjects.

Causes of the rise in prevalence of diabetes in Asian-Indians:

Genetic predisposition: Several studies on migrant Indians across the globe have shown that Asian Indians have an increased risk for developing type 2 diabetes and related metabolic abnormalities compared to other ethnic groups. Although the exact reasons are still not clear, certain unique clinical and biochemical characteristics of this ethnic group collectively called as the “Asian Indian phenotype” is considered to be the cause for the increased susceptibility towards diabetes.

Despite having lower prevalence of obesity as defined by body mass index (BMI), Asian Indians tend to have greater waist circumference and waist to hip ratios thus having a greater degree of central obesity. Again, Asian Indians have more total abdominal and visceral fat for any given BMI and for any given body fat they have increased insulin resistance.

They have lower levels of the protective adipokine adiponectin and have increased levels of adipose tissue metabolites and higher high sensitive C-reactive protein levels.

Studies on neonates suggested that Indian babies are born smaller but relatively fatter compared to Caucasian babies and are referred to as “the thin fat Indian baby”. A recent study confirmed this finding and suggested that the “thin fat phenotype” in neonates persisted in childhood and could be a forerunner of the diabetogenic adult phenotype. Studies have shown that while some genes seem to confer increased susceptibility to diabetes in Indians, some protective genes in Europeans do not appear to protect Indians.

However, the primary driver of the epidemic of diabetes is the rapid epidemiological transition associated with changes in dietary patterns and decreased physical activity as evident from the higher prevalence of diabetes in the urban population.

The Epidemiological Transition: The dramatic rise in the prevalence of type 2 diabetes and related disorders like obesity, hypertension and the metabolic syndrome could be related to the rapid changes in life style that has occurred during the last 50 yr. Although this “epidemiological transition”, which includes improved nutrition, better hygiene, control of many communicable diseases and improved access to quality healthcare have resulted in increased longevity, it has also led to the rapid rise of the new-age diseases like obesity, diabetes and heart disease. The explosion of type 2 diabetes can be explained by the Neel’s ‘thrifty genotype’ hypothesis. This hypothesis proposes that some genes are selected over previous millennia to allow survival in times of famine by efficiently storing all available energy during times of feast. However, these very genes lead to obesity and type 2 diabetes when exposed to a constant high energy diet.

In virtually all populations, higher fat diets and decreased physical activity and sedentary occupational habits have accompanied the process of modernization which has resulted in the doubling of the prevalence of obesity and type 2 diabetes in less than a generation.

One point worth emphasizing is that diabetes can now; no longer be considered as a disease of the rich. The prevalence of diabetes is now rapidly increasing among the poor in the urban slum dwellers, the middle class and even in the rural areas. This is due to rapid changes in physical activity and dietary habits even among the poorer sections of the society. Unfortunately the poor diabetic subjects delay taking treatment leading to increased risk of complications.

Moreover, as the epidemic matures and reaches the next stage of transition, the rich and affluent will rapidly change their activity patterns and start making healthier food choices and ultimately the diabetes and heart disease will decrease in this section of the society. This has been demonstrated in the developed world where the prevalence of diabetes and cardiovascular diseases are higher among the lower socio-economic group and in rural areas compared to higher socio-economic group and urban areas.

Early Identification and Prevention - The Indian Diabetes Risk Score (IDRS)

Hence early identification of the risk factors associated with diabetes and appropriate interventions aimed at preventing the onset of diabetes and its complications are urgently required. Several prospective studies have shown that measures of lifestyle modification help in preventing the onset of diabetes. The Indian Diabetes Prevention Programme (IDPP) has clearly documented the importance of physical activity in the prevention of diabetes. To detect high risk individuals, risk scores based on simple anthropometric and demographic variables have been devised - Indian Diabetes Risk Score (IDRS).

IDRS use four simple variables namely: age, family history, regular exercise and waist circumference. The individuals were classified as having high risk (score >60), moderate risk (score 30-50) and low risk (score <30) out of a total score of 100. IDRS has a sensitivity and specificity of over 60 per cent for a cut-off >60 and can be used to do a selective screening for Indian population.

A recent study showed that IDRS not only predicted diabetes, but also identified individuals with higher cardiovascular risk i.e., those with metabolic syndrome even at a stage when they have normal glucose tolerance. This simple and cost effective IDRS could thus serve as a tool for a primary care physician or a health worker to identify at risk individuals for both diabetes and cardiovascular diseases.

Indian Diabetes Risk Score (IDRS)
Particulars	Score
Age (yr):
< 35	0
35-49	20
>50	30
Abdominal obesity:
Waist <80 cm (female), <90 (male)	0
Waist > 80-89 cm (female), >90-99 cm (male)	10
Waist >90 cm (female), >100 cm (male)	20
Physical activity:
Vigorous exercise or strenuous (manual) labour at home/work	0
Mild to moderate exercise or mild to moderate physical activity at home/work	20
No exercise and sedentary activities at home/work	30
Family history:
No family history	0
Either parent	10
Both parents	20
Minimum score	0
Maximum score	100

IDRS - Interpretation:

Ø Score < 30 low risk for type 2 diabetes and cardiovascular diseases.

Ø Score 30-50 medium risk for type 2 diabetes and cardiovascular diseases.

Ø Score > 60 high risk for type 2 diabetes and cardiovascular diseases.

Diabetes Prevention Guidelines:

You are more likely to develop type 2 diabetes if

you are overweight
you are 45 years old or older
you have a parent, brother, or sister with diabetes
your family background is African American, American Indian, Asian American, Hispanic American/Latino, or Pacific Islander
you have had gestational diabetes or gave birth to at least one baby weighing more than 9 pounds
your blood pressure is 140/90 or higher, or you have been told that you have high blood pressure
your HDL cholesterol is 35 or lower, or your triglyceride level is 250 or higher
you are fairly inactive, or you exercise fewer than three times a week