module2 mortality standardization

Crude Mortality Rate

Total deaths from all causes / total population (per 100,000 per year). Not adjusted for age.

Cause-Specific Mortality Rate

Deaths from one cause / total population (per 100,000 per year).

Age-Specific Mortality Rate

Deaths in one age group / population of that same age group (per 100,000 per year).

Years of Potential Life Lost (YPLL)

Counts the years of life lost to early deaths (before a set age like 75). It gives more weight to deaths of young people.

Live Birth Rate

Live births / total population (per 1,000 per year).

Infant Mortality Rate

Deaths of babies under 1 year / live births in the same time (per 1,000 live births).

Birth Defect Rate

Babies born with defects / total births (per 10,000 births).

Morbidity Rate

How common illness is in a population (existing plus new cases), often per 100 people per year.

Attack Rate

People who got sick / people at risk during an outbreak. It is calculated like cumulative incidence.

Case Fatality Rate (CFR)

Deaths from a disease / people who have the disease x 100. Shows how deadly the disease is.

Survival Rate

1 - case fatality rate. The share of people with the disease who stay alive.

Why Are Crude Rates Misleading for Comparisons?

Populations have different age mixes. An older population has more deaths even if its health care is just as good.

Purpose of Standardization

Removes the effect of age (or another factor) so death rates from different populations can be compared fairly.

Direct Standardization Idea

Asks: what would each population's death rate be if both had the SAME age mix (a standard population)?

Direct Standardized Rate Formula

Add up (age-specific death rate x weight) across all age groups. Weight = the share of the standard population in that age group.

Direct Standardization Steps

1) Choose a standard population. 2) Get its weights (% in each age group). 3) Multiply each age group's death rate by its weight. 4) Add them up.

Direct Standardization: Data Needed

Age-specific death rates for each study population, plus the age breakdown of a standard population.

Does the Choice of Standard Population Matter?

Yes. An older standard population gives more weight to the high death rates at older ages, so adjusted rates go up.

Are Standardized Rates 'Real' Rates?

No. They are made-up (hypothetical) numbers used only to compare populations fairly.

Indirect Standardization: When to Use

When you don't have age-specific death counts for your study group (e.g., workers at one factory or a small group).

Expected Deaths (Indirect Standardization)

How many deaths you would see in your group if it had the same age-specific death rates as the general population. Add up (general death rate x people in your group) for each age group.

Observed Deaths

The actual number of deaths counted in your study group.

Standardized Mortality Ratio (SMR) Formula

SMR = (observed deaths / expected deaths) x 100.

SMR = 100

Observed deaths equal expected deaths. Your group dies at a normal rate.

SMR > 100

More deaths than expected.

SMR < 100

Fewer deaths than expected.

Direct vs. Indirect Standardization

Direct asks: what if both groups had the same age mix? Indirect asks: how many deaths would we expect in this group, and how many did we actually see?

Healthy Worker Effect

Workers can look healthier than the general public because very sick people can't work. It is a type of selection bias.

Interpretation Template: Directly Standardized Rate

If [population] had the same age structure as the standard population, its death rate would be [rate] per [1,000 or 100,000].

Interpretation Template: SMR

The group had [SMR - 100]% MORE deaths than expected (SMR above 100), or [100 - SMR]% FEWER (SMR below 100), compared with the general population.