Public Health: Principles, determinants of health and inequalities

🌍 Principles, determinants of health and inequalities. Public health is "the science and art of preventing disease, prolonging life and promoting health through the organised efforts of society" (Acheson, 1988). Most of what determines health - income, education, housing, work, environment and behaviour - lies outside the NHS. This chapter covers the domains of public health, the determinants of health, health inequalities and how public health is organised in the UK. These themes run through the UKMLA content map and form part of every doctor's professional responsibilities.
Your four questions for any population health problem: Who is affected, and how unequally? What are the underlying (upstream) causes? Which interventions work at population level? Who is responsible for acting?

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What Is Public Health?

• Focus on populations rather than individuals - the "patient" is a community, and the "treatment" is often policy, environment or services.
• Core values: prevention, equity, social justice, evidence-based action, partnership working.
• Historical milestones: John Snow and the Broad Street pump (cholera, 1854 - founding of epidemiology); the Public Health Acts (1848, 1875 - sanitation); Edwin Chadwick's sanitary reforms; vaccination (Jenner); the Black Report (1980 - health inequalities); the Clean Air Act (1956); seatbelt legislation (1983); smoke-free legislation (2007 in England).
• The greatest gains in life expectancy came from clean water, sanitation, nutrition, housing and vaccination rather than medical treatment (the McKeown thesis - debated, but the principle stands).

The Domains of Public Health

Domain	Examples
Health improvement	Lifestyle (smoking, alcohol, diet, physical activity), education, housing, employment, community development, tackling inequalities
Health protection	Infectious disease control, immunisation, outbreak management, environmental hazards (air pollution, chemicals, radiation), emergency preparedness
Healthcare public health (service quality)	Commissioning and planning services, clinical effectiveness, equity of access, audit and evaluation, health economics

• Supported by public health intelligence (data, surveillance, epidemiology) and academic public health (research).
• Prevention levels:
  • Primordial - preventing risk factors developing (e.g. sugar tax, urban design for activity).
  • Primary - preventing disease onset (immunisation, smoking cessation, statins in high-risk people).
  • Secondary - early detection to halt progression (screening, BP checks).
  • Tertiary - reducing complications and disability in established disease (cardiac rehabilitation, diabetic foot care).
  • Quaternary - protecting patients from overmedicalisation and unnecessary intervention.

Population and High-risk Approaches

• Rose's prevention paradox (Geoffrey Rose, 1981): "a large number of people exposed to a small risk may generate many more cases than a small number exposed to a high risk". A measure that brings large benefits to the community offers little to each participating individual.
• High-risk approach - identifies and treats individuals at high risk (e.g. statins for QRISK3 ≥10%). Appropriate for individuals and motivating, but it misses most cases (which arise in the many at moderate risk) and does not change underlying causes.
• Population approach - shifts the whole distribution of a risk factor (e.g. salt reduction in processed food, sugar levy, minimum unit pricing for alcohol, smoke-free laws). A small shift in the population mean prevents more disease overall.
• Both are needed and are complementary.
• Nuffield intervention ladder - from least to most intrusive: do nothing/monitor → provide information → enable choice → guide choice by changing the default → guide by incentives → guide by disincentives (e.g. taxation) → restrict choice → eliminate choice (e.g. ban).

Determinants of Health

• Dahlgren and Whitehead "rainbow" model (1991) - layers of influence around the individual:
  • Fixed factors: age, sex, constitutional (genetic) factors.
  • Individual lifestyle factors: smoking, alcohol, diet, physical activity, sexual behaviour.
  • Social and community networks: family, friends, social support, isolation.
  • Living and working conditions: education, work environment, unemployment, water and sanitation, healthcare services, housing, agriculture and food production.
  • General socioeconomic, cultural and environmental conditions: national policy, economy, climate.
• Estimated contributions to health outcomes (varies by model): health behaviours about 30–40%, socioeconomic factors about 40%, clinical care about 10–20%, physical environment about 10%.
• Commercial determinants of health - industries (tobacco, alcohol, ultra-processed food, gambling, fossil fuels) shape health through marketing, product design, pricing and lobbying.
• Adverse childhood experiences (ACEs) - abuse, neglect, household dysfunction - are linked in a dose–response way with adult smoking, alcohol misuse, mental illness and chronic disease.

Health Inequalities in the UK

• Health inequalities - avoidable, unfair and systematic differences in health between groups.
• Dimensions: socioeconomic deprivation (measured by the Index of Multiple Deprivation, IMD), geography (north–south divide, coastal communities), protected characteristics (ethnicity, disability, sex, sexual orientation), and inclusion health groups.
• Life expectancy gap in England between the most and least deprived tenths of areas is about 10 years for men and 8 years for women; the healthy life expectancy gap is about 19 years.
• The social gradient - health worsens in a stepwise fashion at every step down the social scale, not only among the poorest (Whitehall studies of civil servants).
• Inverse care law (Julian Tudor Hart, 1971): "the availability of good medical care tends to vary inversely with the need for it in the population served".
• Examples: smoking prevalence is several times higher in routine and manual occupations and in people with serious mental illness; infant mortality is higher in the most deprived areas and among Black and Asian babies; maternal mortality is around three to four times higher in Black women than White women in the UK (MBRRACE-UK); people with learning disabilities die on average about 20 years earlier (LeDeR).
• Equality and equity: equality is giving everyone the same; equity is giving according to need so that outcomes become fair.

The Marmot Reviews and Proportionate Universalism

• Fair Society, Healthy Lives (Marmot Review, 2010) - six policy objectives:
  • Give every child the best start in life.
  • Enable all children, young people and adults to maximise their capabilities and have control over their lives.
  • Create fair employment and good work for all.
  • Ensure a healthy standard of living for all.
  • Create and develop healthy and sustainable places and communities.
  • Strengthen the role and impact of ill-health prevention.
• Health Equity in England: The Marmot Review 10 Years On (2020) - found life expectancy had stalled and inequalities widened, especially for women in deprived areas; added objectives on tackling discrimination and environmental sustainability.
• Proportionate universalism - actions should be universal but with a scale and intensity proportionate to the level of disadvantage (e.g. universal health visiting with enhanced support for families in need).
• Marmot places - local areas adopting the Marmot principles (e.g. Coventry).

Inclusion Health and Core20PLUS5

• Inclusion health groups - people who are socially excluded and have extremely poor health: people experiencing homelessness, Gypsy, Roma and Traveller communities, vulnerable migrants and asylum seekers, sex workers, people in contact with the justice system, people who use drugs, victims of modern slavery.
• Homelessness - average age at death is in the mid-40s; high rates of TB, hepatitis C, mental illness, alcohol and drug harm. Anyone can register with a GP without proof of address or identity.
• Core20PLUS5 (NHS England) - a framework to reduce healthcare inequalities: the most deprived 20% of the population (Core20), PLUS locally defined groups (e.g. ethnic minorities, inclusion health groups, coastal communities), and 5 clinical areas for adults: maternity (continuity of carer), severe mental illness (annual health checks), chronic respiratory disease (vaccination uptake), early cancer diagnosis, and hypertension case-finding (plus smoking cessation as a cross-cutting theme). There is a separate children and young people version (asthma, diabetes, epilepsy, oral health, mental health).
• Reasonable adjustments (Equality Act 2010) - e.g. longer appointments, easy-read information, interpreters, annual health checks for people with learning disability aged 14+.

Measuring Population Health

• Mortality rates: crude death rate; age-specific rates; age-standardised mortality rates (direct standardisation - apply the study population's rates to a standard population; indirect standardisation - gives the standardised mortality ratio, SMR = observed ÷ expected deaths × 100).
• Infant mortality rate - deaths under 1 year per 1,000 live births (a sensitive indicator of population health); neonatal (<28 days), perinatal (stillbirths plus deaths in the first week per 1,000 total births), maternal mortality ratio (per 100,000 maternities).
• Life expectancy - average years a newborn would live if current age-specific death rates continued (a period measure, not a prediction).
• Healthy life expectancy (HLE) and disability-free life expectancy - years lived in good health.
• Disability-adjusted life years (DALYs) = years of life lost (YLL) + years lived with disability (YLD); used in the Global Burden of Disease study. Quality-adjusted life years (QALYs) are used in economic evaluation (see the Health Economics chapter).
• Potential years of life lost (PYLL) - emphasises premature deaths.
• Morbidity data sources: GP records (QResearch, CPRD), Hospital Episode Statistics, disease registers (cancer registries), notifications, surveys (Health Survey for England), the census.
• Fingertips (OHID) - online public health profiles for local areas.

Demography and the Ageing Population

• Demographic transition - from high birth and death rates to low birth and death rates, with population growth in between; most high-income countries are in the late stage.
• Population pyramids - wide base (high fertility, young population) versus rectangular or inverted (low fertility, ageing population).
• UK ageing: the number of people aged 85+ is projected to roughly double over the next 25 years; implications include multimorbidity, frailty, dementia, social care demand and workforce needs.
• Dependency ratio - (people under 16 + people of pension age) ÷ working-age population.
• Epidemiological transition - from infectious to non-communicable diseases as leading causes of death (in the UK: dementia, ischaemic heart disease, cerebrovascular disease, lung cancer, COPD).

Public Health Structures in the UK

• England:
  • Department of Health and Social Care (DHSC) - national policy; the Office for Health Improvement and Disparities (OHID) sits within DHSC (health improvement, data and inequalities).
  • UK Health Security Agency (UKHSA) - from 2021, replacing Public Health England's health protection functions: infectious disease surveillance, outbreak response, immunisation policy (with the JCVI), environmental hazards, emergency preparedness.
  • Local authorities - since 2013 (Health and Social Care Act 2012), responsible for public health through the Director of Public Health (DPH) and the ring-fenced public health grant: sexual health services, drug and alcohol services, health visiting and school nursing (0–19 services), NHS Health Checks, smoking cessation, weight management.
  • Health and wellbeing boards - bring together local authority, NHS and community partners; produce the Joint Strategic Needs Assessment (JSNA) and joint health and wellbeing strategy.
  • NHS England and ICBs - commission screening and immunisation programmes (through NHS public health functions agreements) and healthcare. NHS England is being brought into DHSC following the 2025 announcement.
• Devolved nations: Public Health Scotland, Public Health Wales, and the Public Health Agency (Northern Ireland).
• Expert committees: JCVI (Joint Committee on Vaccination and Immunisation), UK National Screening Committee (UK NSC), NICE (public health guidance).
• International: World Health Organization (WHO) and its International Health Regulations (2005).

The Doctor's Public Health Role

• Every doctor has public health duties (GMC Outcomes for graduates; Good medical practice): health promotion, notifying infectious diseases, reporting adverse drug reactions (Yellow Card), safeguarding, antimicrobial stewardship and reducing health inequalities.
• Making Every Contact Count (MECC) - using routine interactions to deliver brief advice on smoking, alcohol, weight and activity.
• Advocacy - speaking up for patients and populations affected by social determinants (e.g. housing conditions such as damp and mould - the death of Awaab Ishak in 2020 led to "Awaab's Law").
• Sustainability - healthcare contributes about 4–5% of UK carbon emissions; the NHS aims for net zero by 2040 (directly controlled emissions) and 2045 (wider footprint).

Public Health at a Glance

Concept	Remember
Three domains	Health improvement, health protection, healthcare public health
Prevention levels	Primordial, primary, secondary, tertiary, quaternary
Rose's paradox	Many at small risk produce more cases than few at high risk
Dahlgren–Whitehead	Rainbow of determinants from individual to societal
Inverse care law	Care is least available where it is most needed
Proportionate universalism	Universal provision scaled to need
England	DHSC/OHID, UKHSA, local authority DPH, ICBs, NHS England (merging into DHSC)

Spot the Answer

• A national programme reduces salt in bread and processed foods. → Population (Rose) approach; primary/primordial prevention.
• Cardiac rehabilitation after MI. → Tertiary prevention.
• A practice in the most deprived area has the fewest GPs per patient. → Inverse care law.
• Who is responsible for commissioning local drug and alcohol treatment services in England? → The local authority (Director of Public Health).
• Avoiding an unnecessary scan in an anxious patient with no red flags. → Quaternary prevention.

Exam-style Scenarios

• Scenario. Two towns have the same crude death rate, but one has a much older population. How should their mortality be compared?
  Answer: Use age-standardised mortality rates (direct standardisation) or SMRs (indirect standardisation), because age confounds crude rates.
• Scenario. A director of public health wants to reduce cardiovascular deaths. Should she fund statins for high-risk people or a population salt-reduction programme?
  Answer: Both have a role. Rose's prevention paradox suggests the population approach prevents more events overall, while the high-risk approach offers greater benefit to each treated individual. A combined strategy, with proportionate universalism to address inequalities, is best.
• Scenario. A man of no fixed abode is told by a receptionist he cannot register without proof of address.
  Answer: Incorrect - NHS England guidance states that lack of proof of address or ID is not a reason to refuse registration. The practice should register him (it can use the practice address) and consider his inclusion health needs.

Key Points

• Most determinants of health lie outside healthcare.
• Health inequalities follow a social gradient; the healthy life expectancy gap is about 19 years in England.
• Population approaches prevent more disease than high-risk approaches alone (Rose).
• Proportionate universalism and Core20PLUS5 guide action on inequalities.
• In England, local authorities lead public health and UKHSA leads health protection.

Guidelines and Further Reading

• Marmot M. Fair Society, Healthy Lives (2010); Health Equity in England: The Marmot Review 10 Years On (2020)
• Rose G. Sick individuals and sick populations. Int J Epidemiol 1985
• Tudor Hart J. The inverse care law. Lancet 1971
• Dahlgren G, Whitehead M. Policies and strategies to promote social equity in health (1991)
• NHS England: Core20PLUS5 - an approach to reducing healthcare inequalities
• OHID: Fingertips public health profiles; ONS: Health state life expectancies by deprivation
• Faculty of Public Health: Public health textbook (healthknowledge.org.uk)