Epidemiology and Disparities
High-Yield Summary
- Incidence = new cases per population at risk, over time. Prevalence = all cases (new + existing) per population, over time. Morbidity = burden/degree of illness. Mortality = deaths caused by a disease.
- Health tracks social class: egalitarian societies (smallest class gaps) have best outcomes. UK's Black Report (1980, Sir Douglas Black): class-based health gaps persisted — and widened — despite the National Health Service/welfare state.
- Second Sickness (Howard Waitzkin, 1983): health outcomes worsened by social injustice, stacked atop biological disease — illustrated by the professional-vs-working-class life expectancy gap.
- Low-income groups: worse self-rated health, more life-shortening chronic disease (lung cancer, diabetes, heart disease), higher suicide/homicide rates, higher infant mortality.
- U.S. lacks centralized healthcare. Affordable Care Act (2010): reduces cost, increases coverage/affordability. Medicare = age/condition-based (65+, end-stage renal disease, ALS), regardless of income. Medicaid = need-based, regardless of age/diagnosis.
- Disparities in care stem from multiple independent mechanisms: access, nutrition, sense of control, smoking/obesity/inactivity, provider bias (incl. weight bias), language/cultural barriers, and discrimination against women and LGBT patients.
Key Terms
- Incidence
- New cases of an illness per population at risk, in a given time.
- Prevalence
- All cases of an illness (new or chronic) per population, in a given time.
- Morbidity vs. mortality
- Morbidity = burden/degree of illness; mortality = deaths caused by the disease.
- Black Report
- 1980 UK report (Sir Douglas Black) finding class-based health gaps persisted/widened despite the welfare state.
- Second Sickness
- Waitzkin (1983): health outcomes worsened by social injustice, a socially produced layer atop biological disease.
- Affordable Care Act (2010)
- U.S. law reducing overall healthcare cost, increasing insurance coverage/affordability.
Incidence vs. Prevalence / Morbidity vs. Mortality
| Term | What It Measures |
|---|---|
| Incidence | New cases only, over a time window |
| Prevalence | All cases (new + existing) at a given time |
| Morbidity | Burden/severity of illness (not death) |
| Mortality | Deaths caused by the disease |
Medicare vs. Medicaid
| Program | Eligibility |
|---|---|
| Medicare | Age/condition-based: 65+, end-stage renal disease, or ALS — regardless of income |
| Medicaid | Need-based: significant financial need — regardless of age/diagnosis |
Common MCAT Trap
- New diagnoses over a study period = incidence; total people currently living with a condition = prevalence — don't swap them.
- Symptom severity/disability/quality-of-life impact = morbidity; death rates = mortality.
- A 70-year-old patient → think Medicare; a low-income patient of any age → think Medicaid.
- A health outcome linked to social injustice (not biology alone) = Second Sickness — don't attribute the class gap purely to biological disease.
Quick Recall
A study counts how many new cases of a disease were diagnosed in a city over the past year. Incidence or prevalence?
A 68-year-old patient with end-stage renal disease needs insurance coverage. Medicare or Medicaid?
Despite universal healthcare, a country's mortality gap between its highest and lowest social classes widens over time. What report/finding does this match?
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