PHPS20010 (Epi 2)_23Jan2025 (Descriptive Epi & Descriptive Studies)

Importance of Measures in Epidemiology

• Current measures provide overall rates known as Crude Rates.

• While useful for assessing disease occurrence, they lack detail.

• Health and disease are not uniformly distributed across populations.

• More specific data are needed for effective health care planning and hypothesis generation.

Disease Distribution

• Understanding disease distribution is essential for targeted public health interventions.

• Factors for analyzing disease distribution:

  • By Person: Characteristics that define afflicted individuals.

  • By Place: Geographic occurrence of diseases.

  • By Time: Temporal patterns of disease prevalence.

Characteristics of 'Person'

• Demographics: Age, gender, ethnicity influence disease impact.

• Socioeconomic Factors:

  • Socioeconomic status, educational level, employment status.

  • Lifestyle factors: smoking, alcohol consumption, nutrition, behavioral aspects.

Age-Specific Rates

• Age is a crucial variable in disease occurrence.

• Infectious diseases often affect children.

• Youths are prone to injuries and violence.

• Chronic conditions have higher incidence and mortality in older adults.

• Age-Specific Rates provide insights into these variations.

Calculating Age-Specific Rates

• Formula: Age-specific Rate = (Number of cases/deaths in age group) / (Population in age group).

• Applies to measures such as incidence, prevalence, morbidity, and mortality rates.

• Specific examples:

  • Age-specific incidence of infectious diseases.

  • Prevalence of Type II Diabetes Mellitus across different age groups.

Covid-19 Mortality Rates

• Analysis of mortality rates among different age groups in various countries.

• Countries involved: Sweden, Netherlands, Italy, etc.

Age-specific Rates of Selected Infectious Diseases

• Examples of predominantly childhood diseases and trends over time.

Limitations of Overall Rates

• Highlighted with case analyses such as Measles and Mumps.

• Crude incidence rates may not accurately reflect disease impact within specific demographics.

Disease Patterns: streptococcus Pneumoniae

• Notably bimodal disease peaks in childhood and older age.

• 2015-2016 data indicating variations in incidence.

Prevalence of Type 2 Diabetes Mellitus in Ireland

• Estimated prevalence rates from different health organizations.

Age-Specific Prevalence of Type 2 DM (2006-2012)

• Age and gender trends in diabetes prevalence.

Morbidity Data

• Statistics on inpatient and day discharge rates in acute hospitals, stratified by age.

Rates Based on Gender

• Gender-specific disease occurrence rates in defined time periods.

• Combined age and gender rates give better insights into health trends.

Characteristics of ‘Place’

• Investigating disease patterns by geographic regions or countries.

• Public health data should consider socioeconomic conditions and healthcare access.

Comparative Cancer Statistics

• Cancer incidence and mortality rates across various European countries.

• Importance of Age-Standardization: Ensuring comparative accuracy for incidence and mortality rates.

Trends Over Time

• Examine how disease occurrence changes due to various factors such as health care advancements and legislative changes.

Infant and Neonatal Mortality Data

• Trends in infant mortality rates over the years.

Age-Standardized Death Rates in Ireland (1992-2011)

• Comparison of mortality from various diseases using standardization methods.

Age-Specific Incidence of Invasive Breast Cancer

• Trends in breast cancer incidence across time periods.

Descriptive versus Analytical Epidemiology

• Descriptive epidemiology focuses on disease rates and distribution (Person, Place, Time).

• Analytical epidemiology investigates determinants of disease and causal relationships.

Case Reports and Case Series

• Case reports detail individual cases, while case series aggregate data.

• Significant for hypothesis generation in clinical research.

• Examples of notable case series illustrating trends in disease associations.

Limitations of Case Studies

• Predominantly comprise anecdotal evidence and do not establish causal relationships.

Prevalence Studies

• Utilized to gauge health service needs through survey methodologies.

• Integrally can help justify resource allocation based on service demand and population health needs.

Factors Affecting Prevalence

• Increased by new cases, longer disease duration, improved diagnostics.

• Decreased by high case-fatality rates and effective cures.

Ecological / Correlational Studies

• Aggregate population data to address health concerns and generate hypotheses.

• Must be cautious not to conflate group data with individual phenomena (ecological fallacy).

Migrant Studies

• Assess disease patterns among migrating populations for insights into environmental versus genetic influences.

• Examples showcase the influence of migration on disease risk.

Conclusion

• Epidemiology employs a variety of study designs to understand disease occurrence and distribution.

• Each approach has its strengths and limitations in assessing public health data.