Describe the epidemiology and prevention of non-communicable diseases.

The Burden and its Determinants

• The four major NCDs, which account for the great bulk of the burden — cardiovascular disease, cancer, chronic respiratory disease and diabetes; with mental illness and injuries now commonly added to make a broader group
• The four shared behavioural risk factors, which is why they are grouped together at all — tobacco use, harmful use of alcohol, unhealthy diet and physical inactivity
• These four produce four metabolic risk factors — raised blood pressure, overweight and obesity, raised blood glucose and raised blood lipids
• The "4 x 4 x 4" framework — four diseases, four behavioural and four metabolic risk factors — is the organising structure of the whole subject, and stating it early shows that the diseases share a common preventive strategy rather than needing four separate ones
• The misconception that NCDs are diseases of the rich must be corrected — the majority of NCD deaths occur in low and middle-income countries, and they occur at younger ages than in high-income countries
• Within India the social gradient has reversed over time — tobacco use, and increasingly obesity and diabetes, are now commoner among the poor, who also have less access to care and bear a far greater proportion of the cost themselves
• Why NCDs matter to a developing economy — they strike during the productive years; they require lifelong and expensive treatment; they are the leading cause of catastrophic health expenditure and of families falling into poverty; and they reduce national productivity and savings
• The INDIAN epidemiological situation — NCDs now cause roughly two-thirds of all deaths, having overtaken communicable disease; but the country simultaneously retains a large communicable, maternal and nutritional burden, and a rising injury burden — the triple burden
• Certain features are specific to South Asia and should be named:
• Coronary disease occurs about a decade earlier than in Western populations, and is more often multi-vessel
• The "thin-fat" Indian phenotype — a higher proportion of body fat, particularly central and visceral fat, at any given BMI, together with greater insulin resistance
• Hence the BMI and waist thresholds for Asians are lower — overweight at 23 and obesity at 25 kg/m², with waist circumference cut-offs of 90 cm in men and 80 cm in women
• The BARKER (DOHaD) hypothesis is directly relevant to India — low birth weight and fetal undernutrition, followed by relative nutritional abundance in later life, programme a higher risk of diabetes, hypertension and coronary disease in adulthood
• This connects India’s two burdens directly — the undernutrition of one generation produces the non-communicable disease of the next, which is why maternal and child nutrition is itself an NCD prevention strategy

Prevention and Control

• The features of NCDs that dictate a different approach from communicable disease — multifactorial causation with NO single agent; long latent period; a prolonged asymptomatic phase, so much disease is undiagnosed; no cure, requiring lifelong management; and outcome determined by continuity of care rather than by a single intervention
• The levels of prevention applied to NCDs:
• Primordial prevention — preventing the risk factors from emerging at all in a population, chiefly by national policy, legislation and taxation. It is the most cost-effective level for NCDs and the one most neglected
• Primary prevention — the population strategy (shifting the whole distribution of risk) and the high-risk strategy (targeting those above a threshold), which are complementary rather than alternative
• Secondary prevention — screening and early treatment, justified for NCDs because the asymptomatic phase is long and effective treatment exists
• Tertiary prevention — preventing complications, rehabilitation and palliative care
• The WHO "best buys" are the interventions with the best evidence and the lowest cost, and listing them is what an examiner rewards:
• Tobacco — raising TAXES (the single most effective measure), smoke-free public places, graphic pack warnings, bans on advertising and promotion, and mass media campaigns
• Alcohol — increasing excise, restricting availability and hours of sale, and banning advertising
• Diet — reducing salt intake through reformulation and labelling, eliminating industrially produced trans fats, and restricting the marketing of unhealthy food to children
• Physical activity — public awareness and building activity into urban design and transport
• Clinical best buys — drug therapy and counselling for those at high cardiovascular risk, cervical cancer screening, and hepatitis B vaccination
• The principle OF total cardiovascular risk assessment is a genuine advance and deserves explanation — treatment decisions should be based on the absolute risk of an event over the next 10 years, combining age, sex, blood pressure, smoking, diabetes and lipids, rather than on any single risk factor exceeding a threshold
• Its practical consequence — an older person with several modest abnormalities may benefit far more from treatment than a young person with one markedly raised value, so treating by threshold alone both over-treats and under-treats
• The population versus high-risk argument applies with special force here — a small downward shift in the whole population’s blood pressure prevents more events than treating everyone above a cut-off, because most events arise from the large number at moderate risk
• Surveillance is required to guide all of this, through the WHO steps approach — step 1 questionnaire on behaviour, step 2 physical measurement, and step 3 biochemical measurement
• IN INDIA the programme is the national programme for prevention and control of non-communicable diseases, delivering population-based screening of all adults over 30 for hypertension, diabetes and the common cancers through the ASHA and the Health and Wellness Centre
• The SDG target is to reduce premature NCD mortality by one third by 2030
• The obstacles to be stated honestly — a health system designed for acute and episodic care; weak primary care for chronic conditions; a large undiagnosed fraction; poor adherence and follow-up; the cost of lifelong medication and out-of-pocket expenditure; commercial opposition from the tobacco, alcohol and food industries; and the long delay between prevention and visible benefit, which makes it politically unrewarding
• Four diseases, four behaviours, four metabolic factors, which is why one preventive strategy serves all of them
• Most NCD deaths occur in poorer countries, and at younger ages, which corrects the commonest misconception
• The Indian social gradient has reversed, so tobacco and increasingly obesity are now commoner among the poor
• Asian BMI thresholds are lower, overweight at twenty-three and obesity at twenty-five, reflecting body composition
• The thin-fat phenotype carries more visceral fat at any given BMI, with greater insulin resistance
• Undernutrition in one generation makes NCDs in the next, which is the Barker hypothesis applied to India
• Maternal nutrition is an NCD prevention strategy, which links the two halves of the Indian burden directly
• Coronary disease strikes a decade earlier in South Asians, and is more often multi-vessel
• Primordial prevention is most cost-effective and most neglected, since its benefit is distant and politically unrewarding
• Taxation is the single most effective tobacco measure, which is why it heads every list of best buys
• Assess total cardiovascular risk, not single factors, since several modest abnormalities may outweigh one severe one
• Treating by threshold both over-treats and under-treats, which is the practical argument for risk-based decisions
• Most events arise from those at moderate risk, which is why population strategies outperform high-risk ones
• NCDs cause catastrophic health expenditure, requiring lifelong treatment and pushing families into poverty
• They strike during the productive years in India, which is why the economic effect exceeds the mortality figures
• The steps approach has three levels — questionnaire, physical measurement and biochemical measurement
• Population screening starts at age thirty under the national programme, delivered through the ASHA and wellness centre
• The SDG target is a third reduction in premature NCD mortality by twenty-thirty
• A long asymptomatic phase justifies screening, which is the specific feature making secondary prevention worthwhile here
• Health systems built for acute care fit badly, since NCDs need continuity rather than episodes
• Commercial opposition is a real obstacle, from tobacco, alcohol and food industries with substantial resources
• Eliminate industrial trans fats, which is among the cheapest and least contested of all the best buys