Diabetes

Type-2 Diabetes in India

Dr A Ramachandran

More about Author

Key Points - Indians have a greater genetic predisposition to diabetes. - Urbanisation and its attendant diet and lifestyle are major contributors to India’s diabetes problem. - Clinicians can make use of a newly developed diabetes risk score for Indians.

Dr A Ramachandran of Chennai’s Diabetes Research Institute analyses the causes of India’s diabetes problem, and proposes some preventative measures.

Type - 2 Diabetes in INDIA

India has approximately 33 million diabetic subjects today and the number is expected to rise to 57.9 million by 2025. More than 95 per cent of them belong to the type - 2 diabetes category. A steady increase in the prevalence of type-2 diabetes has been noted in the last decade in several parts of India. The first estimate was done in 1971 by the Indian Council of Medical Research (ICMR) when the prevalence was estimated at 1.2 per cent, and in 2000 the estimate was at 12.1 per cent.

A wide urban-rural difference in the rates of prevalence of diabetes was evident in the last decade (a four-fold difference). Now,the impact of urbanisation is being felt in the rural population, which has also resulted in changes in their lifestyle. As a consequence there is an increase in the prevalence of diabetes in the rural population, too (from 2.2 per cent to 6.4 per cent). There is also an increasing incidence of impaired glucose tolerance (IGT) in both the rural and urban population. The epidemic of diabetes in India needs to be viewed within a larger demographic and socioeconomic context. India is the world’s second most populous country and has diverse groups of people in terms of caste, religion, habitat, socioeconomic status, education, lifestyles and food habits, etc.

Epidemiological studies conducted over the years have identified several risk factors associated with diabetes. These risk variables are similar across all countries, but their expression and intensity vary widely between races and between geographical regions. It is well known that there is a strong interaction between genetic and environmental risk factors. Indians are at a high genetic risk of diabetes and there seem to be multiple environmental factors, which are independently associated with diabetes.

Acquired Risk Factors

  • Age
  • Family History of Diabetes

Environmental Risk Factors

  • Central Obesity
  • Body Mass Index (BMI)
  • Waist-hip Ratio
  • Insulin Resistance
  • Physical Inactivity and Sedentary
  • Occupation
  • Urbanisation
  • Gestational Diabetes
  • Stress

Genetic Factors

Indians have a high genetic propensity for diabetes. Racial predisposition is evident from studies of migrant Indians. Asian-Indian migrants living in different countries have high rates of glucose intolerance compared with inhabitants of other racial origins. Evidence for a genetic component comes from the increased concordance of diabetes in monozygotic twins, a high prevalence in the offspring of diabetic parents and a high prevalence in certain ethnic groups. Type-2 diabetes is a polygenic disorder, with many candidate genes identified in different populations, but none has been shown to be involved in the development of the disorder.

Family History of Diabetes

The risk of developing diabetes increases above 50 per cent for offspring with a parental history of the illness and it is around 40 per cent if the proband has a diabetic sibling. Familial aggregation of diabetes with a high prevalence among first-degree relatives and vertical transmission through more than two generations is commonly seen in Asian-Indians.

Age-Related Risk

Indians develop diabetes at a very young age – at least 10–15 years earlier than the white population. The National Urban Diabetes Study (NUDS) showed that more than 50 per cent of diabetic subjects developed the disorder before the age of 50. Another analysis by the International Diabetes Epidemiology Group comparing the profile of type-2 diabetes in the European and Asian populations showed that Indians had the strongest age-associated risk for diabetes when compared with other Asian populations or Europeans.

Obesity and Central Adiposity

The association of obesity with type-2 diabetes is complex and is compounded by several heterogeneous factors. Asian-Indians have a leaner BMI than many other races, but BMI is strongly associated with glucose intolerance, as in other populations. This suggests that increased bodyweight, even within the ideal levels of BMI, confers high risk in this population. Even within an acceptable body weight range, weight gain could increase the risk of diabetes, especially in the presence of a familial predisposition. The healthy BMI for an Asian Indian is likely to be <23kg/m2 as suggested by studies in Indian migrants in the US and by our study. Even small increments in body weight produce adverse changes in insulin sensitivity and in blood glucose level.

Insulin Resistance and Metabolic Syndrome

Diabetes - ChartInsulin resistance is a characteristic featureof Asian-Indians, despite low BMI. Insulin resistance worsens with small increments in weight and also with lack of physical activity, a characteristic of modern living,with weight gain and decreased energy expenditure contributing further to the existing insulin inertia. In addition, Indians have a higher body fat content than the Western population.

Impaired Glucose Tolerance

Impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) are considered the forerunners of diabetes and both conditions have a high risk of conversion to diabetes. These stages are not only an indicator of future diabetes, but also an index of impending rise in cardiovascular diseases. Prevalence of IGT is high in Indians, showing the existence of a large pool of individuals susceptible to diabetes. IGT occurs at a young age in Indians.

Urbanisation

A transition from a traditional to a modern life has produced several health hazards in many populations,including the Asian-Indians. Urbanisation is associated with increasing obesity,decreasing physical activity and other risk factors associated with diabetes development. The adverse effects are evident from the rising prevalence of diabetes even among the rural population. A recent study in Tamilnadu showed that the prevalence had increased nearly three-fold in a span of 14 years in the rural population (2.2 per cent in 1989 to 6.4 per cent in 2003).

Gestational Diabetes

Gestational diabetes (GDM) is a strong indicator of future diabetes. It is major health hazard in women as it adversely affects both maternal and foetal outcomes of the pregnancy unless a tight glycaemic control is maintained. It was reported that 34 per cent of Danish women with previous diet-treated GDM had abnormal glucose tolerance 11 to 12 years after pregnancy compared with 5 per cent in a control group.

Stress Factors

The impact of stress, both physical and mental, is very strong on diabetogenesis, especially in those with a strong genetic background. A clinic-based prospective study from our centre has clearly shown the effect of stress on diabetes.

A Risk Score for Indians

Recently, a risk score has been developed,specifically for the Indian population, based on the risk assessments made in our epidemiological studies. This simple score can be used in any clinic setting without any special investigation.

Variables Risk Score
Age (30-44) years 10
Age (45-59) years 18
Age (>59) years 19
FH-DM 7
BMI (=25) kg/m² 7
Waist (M=>85cm, W=>80cm) 5
Sedentary Physical Activity 4
   
Maximum Score 42

Prevention of Diabetes

Prevention of type-2 diabetes is possible with changes in lifestyle. While the genetic component for the development of diabetes cannot be corrected, the environmental factors can be modified. Obesity, diet and physical activity are the modifiable factors. The interaction of diet and exercise influences the body fat pattern, which has a significant role in determining insulin sensitivity. Traditional lifestyles, characterised by a diet including less saturated fat and complex carbohydrates, and greater physical activity, may protect against the development of cardiovascular risk factors and diabetes, even in the presence of a potential genetic predisposition.