Population Health Case Studies

Population Health Case Studies

Epidemiology

• Epidemiology is the study of the distribution and patterns of health events, health characteristics, and their causes or influences in well-defined populations.
• This course focuses on population health, not individual health.
• Clinical or personal health courses focus on individual health conditions, risk factors, and treatment outcomes, starting with an individual's history.

Importance of Studying Population Health

• Global issues are local issues.
• Examples of global issues include:
  • Global Burden of Disease (GBD) project
  • COVID-19
  • Non-communicable diseases
  • Obesity epidemic
  • A rights-based approach to Māori health
  • HIV/AIDS
  • Climate change and health
  • Health of young people

Global Burden of Disease (GBD) Project Overview

• Lecture 27 provides an overview of the Global Burden of Disease (GBD) project.
• Learning objectives:
  • Describe the reasons, aims, and major impacts of the GBD project.
  • Define Disability Adjusted Life Year (DALY) and its data elements.
  • Understand the leading causes and risk factors contributing to deaths and disability in New Zealand and globally.
  • Identify the major gains and limitations of the DALY approach to measuring disability.
  • Recognize the distinctions between the Medical and Social models of disability.

True/False Questions

• Disability Adjusted Life Year (DALY) is the summary measure that considers both fatal and non-fatal disease outcomes - True.
• DALYs are measured using the data elements: Years Lived with Disability (YLD) and Years of Life Lost to mortality (YLL) - True.
• DALYs are not a good measure to assess changes of the disease burden over time - False.
• A higher burden of deaths at a younger age contributes a lot of YLLs to the DALY burden - True.
• Prior to the Global Burden of Disease (GBD) project, priority-setting was largely based on mortality data - True.

Reasons for Prioritizing Health

• Health resources are finite (limited).
• Rationing involves ethical as well as evidence-based judgment.
• Each prioritization has an opportunity cost.
• It is difficult to compare outcomes (mortality & disability).
• There's a distinction between individual (clinical services) vs. population needs (population health services).

Reasons for the Global Burden of Disease (GBD) Project

• Data on the burden of disease and injury from many countries were incomplete.
• Available data largely focused on deaths, with little information on non-fatal outcomes (disability).
• Lobby groups can give a distorted image of which problems are most important.
• Unless the same approach is used to estimate the burden of different conditions, it is difficult to decide which conditions are most important and which strategies may be the “best buys.”

Impact of the GBD Project

• GBD 1990: World Bank commissioned the original GBD study, featured in the World Development Report: Investing in Health; Christopher Murray & Alan Lopez.
• GBD 2006: Had a profound impact on policy and brought global attention to otherwise hidden or neglected health challenges. Researchers from Harvard and WHO collaborated.
• GBD 2010: Next most comprehensive GBD update along with methods, involving about 500 experts across the world and funded by the Bill and Melinda Gates Foundation.
• GBD 2013: Expanded on methodology, tools, estimates, datasets, and presents estimates of all-cause mortality, YLLs, YLDs, DALYs by country, age, and sex, reflecting work of 1000 researchers across more than 100 countries.

Aims of the GBD Project

1. To use a systematic approach to summarize the burden of diseases and injury at the population-level based on epidemiological principles and best available evidence.
   • To aid in setting health service and health research priorities.
   • To aid in identifying disadvantaged groups and targeting of health interventions.
2. To take account of deaths as well as non-fatal outcomes (i.e., disability) when estimating the burden of disease.
   • Disability Adjusted Life Years (DALYs) was the specific measure developed to achieve these aims.

Disability Adjusted Life Years (DALYs)

• The summary measure of population health that combines data on premature mortality (fatal) and non-fatal health outcomes to represent the health of a particular population as a single number.

DALY = YLD + YLL

• Where:
  • DALY = Disability Adjusted Life Year
  • YLD = Years Lived with Disability
  • YLL = Years of Life Lost

Years of Life Lost (YLL)

• Represents mortality by counting the years lost due to premature death caused by a disease (the years lost if a person dies before reaching the average life expectancy in a particular country).
• Data points required to calculate YLL:
  • Number of deaths from the disease in a year.
  • Years lost per death relative to an ‘ideal’ age (life expectancy).
• Example:
  • If a person dies at 50 years old and the life expectancy is 81 years, then 31 years are lost.

Years Lived with Disability (YLD)

• Represents morbidity by counting the years lived with the disease.
• Data points required to calculate YLD:
  • Number of cases with non-fatal outcome with the disease
  • Average duration of non-fatal outcome until recovery/ death
  • Disability weight (e.g. lung cancer - 0.29)
• Scale:
  • A year in perfect health = 0
  • A year of life lost to death due to a health condition = 1
  • A year lived with disability = between 0 and 1
  • A DALY represents a lost healthy life year

Uses of DALYs

• Enables comparisons between diseases by using a summary measure that considers fatal (premature death) and non-fatal (disability) outcomes.
• Enables comparison between diseases to:
  • Prioritize health issues, risks, and interventions.
  • Monitor health interventions.
  • Assess changes of disease burden over time.

GBD Terms

• Communicable diseases (infectious diseases), e.g., diarrhea, TB, measles, HIV/AIDS, malaria. Group 1 conditions in the GBD project includes communicable diseases AND problems in pregnancy, childbirth, or early life (perinatal conditions).
• Non-communicable diseases (NCDs) / chronic diseases (e.g., heart disease, strokes, cancer, diabetes). Group 2 conditions in the GBD project.
• Injury: Group 3 conditions in the GBD project.
• High-Income Countries (HICs) / Low-Income countries (LICs) / Low- and Middle-Income Countries (LMICs).

GBD Example

• Ischaemic heart disease (health outcome) is caused by smoking or obesity.

Leading Causes of DALYs – Global (both sexes and all ages)

• Perinatal, nutritional, and Communicable Diseases
• Non-Communicable Diseases
• Injuries

Leading causes of DALYS – New Zealand (both sexes and all ages)

• 85% Non-communicable Disease (NCDs)
  • 17% cancers
  • 14% Cardiovascular disease
  • 11% Musculoskeletal disorders
  • 10% Mental Disorders
  • 7% Neurological disorders
  • 6% Other NCDs
  • 5% Chronic Respiratory Diseases
  • 4% Diabetes & Kidney Disease
  • 3% Sense Organ Diseases
  • 3% Substance use disorders
  • 2% Digestive Diseases
  • 2% Skin & Subcutaneous disease
• 12% Injuries
  • 7% Unintentional
  • 2% self-harm + interpersonal violence
  • 2% Transport
• 3% Communicable, maternal, neonatal and nutritious diseases

Group Classifications in GBD

• Group I: Communicable, maternal, perinatal, and nutritional conditions.
• Group II: Non-communicable diseases.
• Group III: Injuries.

Gains of the DALY Approach

1. Drew attention to the previously hidden burden of mental health problems and injuries as major public health problems.
2. Recognizes Non-Communicable Diseases (NCDs) as a major and increasing problem in low- and middle-income countries (not just a rich country problem).

Challenges in Using DALYs to Quantify the Burden of ‘Disability’

1. Disability weights are considered to be the same as the severity of an impairment relating to a disease/health condition and do not vary with a person’s social position, where they live, their access to healthcare, or any other life circumstance.
2. The GBD project is criticized for its potential to represent people with disabilities as a ‘burden’.

Medical Model of Disability

• Focus: Individual impairment.
• Causes: Individual conditions, deficits.
• Solution: Medical intervention, rehabilitation.
• Perspectives: Individual is dependent and needing to be cured or cared for.
• Control: The ‘helping’ expert (paternalistic approach).
• Goal: “Fixing” the individual.
• Perpetuates negative stereotypes about people with disabilities.
• Example: A wheelchair user - The disabling factor: The physical limitation, needing medical assistance or specialized devices to participate in society.

Social Model of Disability

• Focus: Societal barriers and attitudes.
• Causes: Social structures, policies, environmental factors, attitudes.
• Solution: Removing barriers, creating inclusive environments.
• Perspectives: Disability as a social construct.
• Control: Removing barriers, creating inclusive environments.
• Goal: Creating a society where everyone can participate fully.
• Example: A wheelchair user - The disabling factor: The inaccessible environment (i.e., the absent ramp that prevents them from accessing a building).