Describe the epidemiology, prevention and control of diabetes mellitus.

Epidemiology and Risk Factors

• The types — type 1, autoimmune beta-cell destruction, usually in the young, requiring insulin from the outset; type 2, characterised by insulin resistance with relative deficiency, accounting for the overwhelming majority and the whole of the public health problem; gestational; and other specific types
• The INDIAN phenotype differs in ways that matter clinically:
• Onset a decade earlier than in Western populations, and at a lower BMI
• Greater central adiposity and insulin resistance at any given weight
• Higher rates of gestational diabetes
• A greater proportion of the burden in rural areas than previously assumed
• The consequence of earlier onset is longer disease duration, and therefore more complications during the productive years — which is why the economic burden in India exceeds what the prevalence figures alone suggest
• The risk factors — non-modifiable: age, family history, ethnicity, previous gestational diabetes and low birth weight
• Modifiable: obesity, particularly central obesity, which is the strongest; physical inactivity; diet high in refined carbohydrate, sugar-sweetened beverages and trans fat; tobacco and alcohol; and stress and sleep deprivation
• The dietary transition in India is a specific driver — a shift toward polished white rice and refined wheat with a high glycaemic index, more edible oil and sugar, and less coarse cereal, millet and fibre
• Diagnosis — fasting plasma glucose 126 mg/dL or above; 2-hour post-glucose value 200 mg/dL or above; HbA1c 6.5% or above; or a random value of 200 mg/dL or above with symptoms
• Prediabetes (impaired fasting glucose or impaired glucose tolerance) is the most important concept for prevention, since a very large number of Indians are in this category and a substantial proportion progress to diabetes each year
• The crucial evidence is that this progression can be prevented — lifestyle modification in those with prediabetes reduces progression by roughly half, and is more effective than metformin, as the Indian Diabetes Prevention Programme confirmed in an Indian population
• That single finding is the strongest argument for screening and for lifestyle intervention, and it is worth stating explicitly rather than merely recommending diet and exercise in general terms

Complications, Screening and Control

• The complications determine the burden, and most are preventable with adequate control:
• Microvascular — retinopathy, a leading cause of preventable blindness in working-age adults; nephropathy, a leading cause of end-stage renal disease; and neuropathy
• Macrovascular — coronary disease, stroke and peripheral arterial disease, which cause most of the mortality
• The diabetic foot is the complication with the greatest preventable burden — arising from neuropathy (loss of protective sensation), ischaemia and infection together, and leading to amputation
• Most amputations are preceded by an ulcer, and most ulcers are preventable by annual foot examination with monofilament testing, patient education, appropriate footwear, nail and skin care, and prompt treatment of any lesion
• The single instruction that prevents the most harm is that a person with neuropathy must not walk barefoot and must inspect the feet daily, since they will not feel the injury that starts the ulcer
• Also important — increased susceptibility to infection, particularly tuberculosis, which is a significant interaction in India, where the two epidemics overlap
• Screening — under the national programme, population-based screening of all adults over 30, with opportunistic screening of those with risk factors; the INDIAN diabetes risk score uses age, waist circumference, physical activity and family history to identify those needing a blood test, which is cheap and requires no laboratory
• Universal screening for gestational diabetes is recommended in India because of its high prevalence, using a single-step 75 g oral glucose test irrespective of the time since the last meal, which suits field conditions
• Gestational diabetes matters doubly — it affects the current pregnancy, and it identifies a woman at high future risk of type 2 diabetes, and a child at higher lifetime risk, so it is an opportunity for prevention across two generations
• Management at population level — lifestyle modification as the foundation for everyone; standard treatment protocols with metformin as first-line; assured supply of affordable drugs including insulin; structured patient education and self-management support; a register with active follow-up; and regular screening for complications — annual eye, foot, renal (urine albumin) and cardiovascular assessment
• Self-management deserves emphasis — the patient makes essentially all the treatment decisions for a chronic disease, since they are with the doctor for perhaps an hour a year, so education is not an optional adjunct but the main intervention
• Prevention at population level — taxation of sugar-sweetened beverages; front-of-pack labelling; restricting marketing of unhealthy food to children; promoting coarse cereals and millets, which India has actively encouraged; urban design supporting physical activity; and school-based programmes
• The barriers in India — a large undiagnosed fraction; poor adherence and follow-up; cost of lifelong medication, monitoring and insulin; limited access to laboratory monitoring in rural areas; low awareness of complications; and inadequate screening for complications, so that retinopathy and nephropathy present late
• Lifestyle change halves progression from prediabetes, and beats metformin, which was shown in an Indian population
• Never walk barefoot with neuropathy, and inspect the feet daily, since the injury that starts the ulcer is not felt
• Most amputations begin as a preventable ulcer, which makes annual foot examination among the highest-value checks
• Use a monofilament to test protective sensation, which is cheap, quick and identifies the feet at risk
• Indian diabetes begins a decade earlier and at a lower BMI, giving longer duration and more complications
• Longer duration means more complications during the productive years, which is why the economic burden exceeds the prevalence
• The Indian Diabetes Risk Score needs no laboratory, using age, waist, activity and family history to select for testing
• Screen all pregnant women universally in India, using a single-step test irrespective of the last meal
• Gestational diabetes is a two-generation opportunity, identifying future risk in both mother and child
• Polished rice and refined wheat raise glycaemic load, which is the specific dietary transition driving Indian diabetes
• Promoting millets and coarse cereals is a dietary policy with a direct metabolic rationale
• Diabetes increases susceptibility to tuberculosis, which matters greatly where the two epidemics overlap
• Retinopathy blinds during working life, and is preventable with annual screening and adequate control
• Macrovascular disease causes most of the mortality, though microvascular complications cause most of the disability
• The patient makes nearly all the decisions, being with a doctor for perhaps an hour a year, so education is the main intervention
• Check urine albumin annually, which detects nephropathy while it is still modifiable
• Metformin is first-line in every protocol, being effective, cheap and weight-neutral
• Insulin cost and cold storage limit access in rural India, which is a practical barrier rather than a clinical one
• Central obesity is the strongest modifiable factor, which is why waist circumference is measured alongside weight
• Low birth weight raises later diabetes risk, linking the disease back to maternal nutrition
• Tax sugar-sweetened beverages, which is among the better-evidenced population measures against diabetes
• The rise is too fast to be genetic, and must therefore be environmental, which is itself an argument for prevention
• Type 2 accounts for the whole public health problem, whatever the clinical interest of the other types
• HbA1c reflects three months of control, and avoids the fasting requirement that limits field testing