Population health: NZ distribution and determinants (last-minute notes)

Population health: essential concepts

Definition: the health outcomes of a group of individuals including the distribution of such outcomes within the group. (Kindig & Stoddart, 2003)
Focus: group-level health and inequities, not only average health.

Social determinants of health (SDOH): the conditions in which people are born, grow, live, work and age, and the wider systems shaping daily life. WHO definition.
Dahlgren-Whitehead framework (highlights layers):
- Individual lifestyle factors (e.g., smoking, diet, physical activity)
- Social and community networks (neighbourhood, housing)
- Living/working conditions (employment, income, education, housing quality)
- Broad socioeconomic, cultural, and environmental conditions (national policies, air quality)

Two important patterns of health distribution in NZ: ethnicity and socioeconomic status (SES).
Life expectancy varies by ethnicity (Māori vs non‑Māori) and by gender; gaps persist across time.
Health outcomes linked to SES: higher disease burden and mortality in more deprived groups, and differences in chronic diseases (e.g., diabetes) and infectious diseases.
Examples from NZ data:
- Diabetes (adults 15+): diagnosed cases by SES (2023/24 data)
- Rheumatic heart disease: hospitalisations by ethnicity (Māori vs non‑Māori), aged 15+ (2012–2014)
- Cancer mortality: Māori vs non‑Māori (2022 preliminary data)
- Unmet need for GP services due to cost (adults 15+, 2023/24)

SES components to consider:
- Occupation
- Education
- Living standards measures (economic living standards index, ELSI)
- Deprivation indices (area-based NZDep)
NZDep2023: area-based measure of deprivation
- Areas with ~100–200 people
- Deciles: 1 ext{ (least deprived)} to 10 ext{ (most deprived)}
- Applies to everyone in the area; determined from address; not an individual label
- Includes a range of deprivation aspects; suitable for population-level analysis
NZDep is a neighbourhood measure, not an individual measure; conveys relative deprivation at population level

Purpose: quantify relative deprivation across neighbourhoods; used for public health planning and monitoring equity
Decile interpretation: lower deciles indicate less deprivation; higher deciles indicate more deprivation
Limitations: not a fixed label for individuals; does not capture all dimensions of deprivation

Absolute poverty: income level below which a nutritionally adequate diet plus essentials is not affordable
- Formal: income insufficient to meet basic needs at a minimum level
Relative poverty: income level below what is considered acceptable relative to society/economy
- Reflects social standards and affordability of basic necessities within a given society

Determinants of health (broad): genetics, behaviors, social position, environment, health services, and policies
Social determinants of health (SDOH) emphasize daily living conditions and broader forces that shape health outcomes
Practical implications: addressing health inequities requires policy and societal interventions beyond individual behavior change

Social gradient: health improves with higher SES; inequities widen with deprivation
Deprivation is linked to multiple health risks (housing quality, crowding, access to care, environmental exposures)

Deprivation is measured at neighbourhood level (NZDep); not an individual risk score
Use NZDep for population-level analyses and to identify areas for targeted interventions
Be aware of ecological fallacy: neighbourhood measures do not determine individual risk alone

Ethnicity and SES drive observed health disparities in NZ: Māori experience lower life expectancy and higher disease burden compared with non-Māori; disparities persist across SES groups
SES-linked conditions: higher diabetes prevalence among lower SES groups; higher rates of rheumatic heart disease and certain infectious diseases in more deprived areas
Access to care: cost-related barriers result in unmet GP needs in some populations

Population health focuses on the health outcomes of groups and how these outcomes are distributed
In NZ, health distribution is shaped mainly by ethnicity and socioeconomic status
NZDep2023 provides a neighbourhood-level measure of deprivation (deciles 1–10)
Absolute and relative poverty describe different concepts of material deprivation
Addressing health inequities requires attention to social determinants and policies that improve living conditions, access to care, and economic opportunity