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Epidemiology of Diabetes Mellitus
Diabetes is a long-term disease with variable clinical manifestations and progression. Chronic
hyperglycaemia, from whatever cause leads to a number of complications - cardiovascular,
renal,neurological, ocular and others such as intercurrent infections.
Classification:
The classification adopted by WHO.
Clinical classification of diabetes mellitus
1. Diabetes mellitus (DM)
i) Type 1 or Insulin-dependent diabetes mellitus
ii) Type 2 or Non-insulin dependent diabetes mellitus
iii) Malnutrition-related diabetes mellitus (MRDM)
iv) Other types (secondary to pancreatic, hormonal, drug induced, genetic and other
abnormalities)
2. Impaired glucose tolerance (IGT)
3. Gestational diabetes mellitus (GDM)
Type 1 diabetes (Insulin-dependent diabetes mellitus) is the most severe form of the disease.
Its onset is typically abrupt and is usually seen in individuals less than 30 years of age. It is
lethal unless diagnosed and treated. This form of diabetes is immune-mediated in over 90 % of
cases and idiopathic in less than 10 % cases. The rate of destruction of pancreatic B cell is quite
variable, rapid in some individuals and slow in others. Type 1 diabetes is usually associated
with ketosis in its untreated state. It occurs mostly in children, the incidence is highest among
10-14 year old group, but occasionally occur in adults. Exogenous insulin is required to reverse
the catabolic state, prevent ketosis, reduce the hyperglucagonaemia, and reduce blood
glucose
Type 2 diabetes is much more common than type 1 diabetes. It is often discovered by chance.
It is typically gradual in onset and occurs mainly in the middle-aged and elderly, frequently
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mild, slow to ketosis and is compatible with long survival if given adequate treatment. Its
clinical picture is usually complicated by the presence of other disease processes.
Impaired glucose tolerance (IGT) describes a state intermediate- "at-risk" group - between
diabetes mellitus and normality. It can only be defined by the oral glucose tolerance test.
Problem statement
WORLD
Diabetes is an "iceberg" disease. Although increase in both the prevalence and incidence of
type 2 diabetes have occurred globally, they have been especially dramatic in societies in
economic transition, in newly industrialized countries and in developing countries.
Currently the number of cases of diabetes worldwide is estimated to be around 347 million, of
these more than 90 % are type 2 diabetes.
In 2008, an estimated 1.2 million people died from consequences of high blood sugar. More
than 80% diabetes deaths occur in low and middle income countries.The prevalence of
diabetes was highest in the Eastern Mediterranean Region and the Region of the Americas (11
% for both sexes) and lowest in the WHO European and Western Pacific Regions (9% for both
sexes).
The estimated prevalence of diabetes was relatively consistent across the income groupings of
countries. Low income countries showed the lowest prevalence {8% for both sexes), and the
upper-middle-income countries showed the highest (10% for both sexes).Un favourable
modification of lifestyle and dietary habits that are associated with urbanization are believed
to be the most important factors for the development of diabetes. The prevalence of diabetes
is approximately twice in urban areas than in rural population.
Natural history
Epidemiological determinants:
1. AGENT
The underlying cause of diabetes is insulin deficiency which is absolute in type 1 diabetes and
partial in type 2 diabetes. This may be due to a wide variety of mechanisms:
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(a) pancreatic disorders - inflammatory, neoplastic and other disorders such as cystic fibrosis.
(b) defects in the formation of insulin, e.g., synthesis of an abnormal, biologically less active
insulin molecule.
c) destruction of beta cells, e.g., viral infections and chemical agents.
(d) decreased insulin sensitivity, due to decreased numbers of insulin receptors.
(e) genetic defects, e.g., mutation of insulin gene.
(f) autoimmunity.
Evidence is accumulating that the insulin response to glucose is genetically controlled. The
overall effect of these mechanisms is reduced utilization of glucose which leads to
hyperglycaemia accompanied by glycosuria.
2. HOST FACTORS
(a)AGE : Although diabetes may occur at any age, surveys indicate that prevalence rises
steeply with age. Type 2 diabetes usually comes to light in the middle years of life and begins
to rise in frequency.
(b} SEX: In some countries {e.g., UK) the overall male-female ratio is Equal. In south-east Asia,
an excess of male diabetics has been observed.
(c) GENETIC FACTORS: The genetic nature of diabetes is undisputed. Twin studies showed that
in identical twins who developed type 2 diabetes, concordance was approximately 90% thus
demonstrating a strong genetic component.
In type 1 diabetes, the concordance was only about 50% indicating that type 1 diabetes is
not totally a genetic entity.
(d) GENETIC MARKERS :Type 1 diabetes is associated with HLA-B8 and B15, and more
powerfully with HLA-DR3 and DR4. The highest risk of type 1 diabetes is carried by individuals
with both DR3 and DR4. On the other hand type 2 diabetes is not HLA-associated.
(e) IMMUNE MECHANISMS : There is some evidence of both cell mediated and of humoral
activity against islet cells. Some people appear to have defective immunological mechanisms,
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and under the influence of some environmental "trigger", attack their own insulin producing
cells.
(f) OBESITY: Obesity particularly central adiposity has been accepted as a risk factor for type 2
diabetes and the risk is related to both the duration and degree of obesity , waist
circumference or waist to hip ratio (reflecting abdominal or visceral adiposity) are more
powerful determinants of subsequent risk of type 2 diabetes than BMI.
(g) MATERNAL DIABETES : Offsprings of diabetic pregnancies including gestational diabetes are
often large and heavy at birth, tend to develop obesity in childhood and are at high risk of
developing type 2 diabetes at an early age , intrauterine growth retardation .
3. ENVIRONMENTAL RISK FACTORS
Susceptibility to diabetes appears to be unmasked by a number of environmental factors
acting on genetically susceptible individuals. They include :
(a) SEDENTARY LIFESTYLE : Sedentary life style appears to be an important risk factor for the
development of type 2 diabetes.
Lack of exercise may alter the interaction between insulin and its receptors and subsequently
lead to type 2 diabetes.
(b) DIET : A high saturated fat intake has been associated with a higher risk of impaired glucose
tolerance, and higher fasting glucose and insulin levels .
Higher proportions of saturated fatty acids in serum lipid or muscle phospholipid have been
associated with higher fasting insulin, lower insulin sensitivity and a higher risk of type 2
diabetes. Higher unsaturated fatty acids from vegetable sources and polyunsaturated fatty
acids have been associated with reduced risk of type 2 diabetes and lower fasting and 2-hour
glucose concentrations.
(c) DIETARY FIBRE : high intakes of dietary fiber have been shown to result in reduced blood
glucose and insulin levels in people with type 2 diabetes and impaired glucose tolerance . A
minimum daily intake of 20 grams of dietary fiber is recommended.
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(d) MALNUTRITION: Malnutrition (PEM) in early infancy and childhood may result in partial
failure of B cell function. Damage to beta cells may well explain the associated impaired
carbohydrate tolerance in kwashiorkor .
(e) ALCOHOL: Excessive intake of alcohol can increase the risk of diabetes by damaging the
pancreas and liver and by promoting obesity .
(f) VIRAL INFECTIONS: Among the viruses that have been implicated are rubella, mumps, and
human coxsackie virus B4. Viral infections may trigger in immunogenetically susceptible
people a sequence of events resulting in B cell destruction.
(g) CHEMICAL AGENTS: A number of chemical agents are known to be toxic to beta cells, e.g.,
rodenticide A high intake of cyanide producing foods (e.g., certain beans) may also have toxic
effects on B -cells.
(h) STRESS : Surgery, trauma, and stress of situations, internal or external, may "bring out“ the
disease.
(i) OTHER FACTORS : High and low rates of diabetes have been linked to a number of social
factors such as occupation, marital status, religion, economic status, education, urbanization
and changes in life style(it is now common in the lower social classes ).
PREVENTION AND CARE:
1. Primary prevention
Two strategies for primary prevention have been suggested:
(a) population strategy (b) high-risk Strategy.
a. POPULATION STRATEGY
The scope for primary prevention of type 1 diabetes is limited on the basis of current
knowledge and is probably not appropriate. However, the development of prevention
programmes for type 2 diabetes based on elimination of environmental risk factors is
possible.
There is pressing need for primordial prevention (prevention of the emergence of risk factors)
in countries in which they have not yet appeared.
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The preventive measures comprise maintenance of normal body weight through adoption of
healthy nutritional habits and physical exercise.
The nutritional habits include an adequate protein intake, a high intake of dietary fiber and
avoidance of sweet foods.
Elimination of other less well defined factors such as protein deficiency and food toxins may
be considered in some populations. These measures should be fully integrated into other
community-based programmes for the prevention of non-communicable diseases (e.g.,
coronary heart disease).
b. HIGH-RISK STRATEGY There is no special high-risk strategy for type 1 diabetes , At present,
there is no practical justification for genetic counselling as a method of prevention.
Since NIDDM appears to be linked with sedentary lifestyle, over-nutrition and obesity,
correction of these may reduce the risk of diabetes and its complications , alcohol should be
avoided. Subjects at risk should avoid diabetogenic drugs like oral contraceptives, reduction of
factors that promote atherosclerosis, e.g., smoking, high blood pressure, elevated cholesterol
and high triglyceride levels. These programmes may most effectively be directed at target
population groups.
2. Secondary prevention
When diabetes is detected, it must be adequately treated.
The aims of treatment are :
(a) to maintain blood glucose levels as close within the normal limits as is practicable
(b) to maintain ideal body weight. Treatment is based on
(a) diet alone - small balanced meals more frequently,
(b) diet and oral antidiabetic drugs,
(c) diet and insulin. Good control of blood glucose protects against the development of
complications.
Proper management of the diabetics is most important to prevent complications.
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Routine checking of blood sugar, of urine for proteins and ketones, of blood pressure, visual
acuity and weight should be done periodically.
The feet should be examined for any defective blood circulation (Doppler ultrasound probes
are advised), loss of sensation and the health of the skin. Primary health care is of great
importance to diabetic patients since most care is obtained at this level.
Glycosylated haemoglobin : There should be an estimation of glycated {glycosylated)
haemoglobin at half-yearly intervals. This test provides a long-term index of glucose control.
(glucose in the blood is complexed to a certain fraction of haemoglobin to an extent
proportional to the blood glucose concentration.
The percentage of such glycosylated haemoglobin reflects the mean blood glucose levels
during the red cell life-time {i.e., about the previous 2-3 months)
Self-care : diabetic should take a major responsibility for his own care with medical guidance -
e.g., adherence to diet and drug regimens, examination of urine and where possible blood
glucose monitoring; self administration of insulin, abstinence from alcohol, maintenance of
optimum weight, attending periodic check-ups, recognition of symptoms associated with
glycosuria and hypoglycaemia
Home blood glucose monitoring.
The patient should carry an identification card showing name, address, telephone number
and the details of treatment receiving.
3. Tertiary prevention
Diabetes is major cause of disability through its complications, e.g., blindness, kidney failure,
coronary thrombosis, gangrene of the lower extremities, etc. The main objective at the tertiary
level is to organize specialized clinics (Diabetic clinics) and units capable of providing diagnostic
and management skills of a high order.
BY:TWANA NAWZAD