Ecological trend analysis is a type of descriptive epidemiological study that examines changes in disease rates, exposures, or health outcomes over time using population-level (grouped) data, rather than individual-level information.

• Unit of analysis: groups or populations (e.g., countries, regions, age cohorts), not individuals.
• Objective: to assess temporal patterns and trends in disease burden, risk factor exposure, or health outcomes.
• Data sources: often derived from national registries, surveys, census data, international databases (e.g., WHO, GBD).
• Commonly used in:
  • Global burden of disease studies
  • Environmental health (e.g., air pollution, climate)
  • Socioeconomic or policy impact assessments
• Methods:
  • Time series analysis
  • Regression models (e.g., Joinpoint, Poisson, or age–period–cohort models)
  • Age-standardized rate comparisons across time

• Useful for generating hypotheses
• Enables cross-national or global comparisons
• Can identify public health priorities and monitor progress over time

• Subject to ecological fallacy — associations at the group level may not hold at the individual level.
• May be affected by confounding variables that vary between groups or over time.

• Ecological study
• Time trend analysis
• Global burden of disease (GBD)