detailed explanation of key measures of mortality, including definitions, formulas, and interpretations for:

• Crude death rate
• Age-specific death rate
• Infant mortality rate
• Neonatal mortality rate
• Adjusted/standardized death rate

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1. Crude Death Rate (CDR)

Definition:

The crude death rate is the total number of deaths in a population over a given period (usually a year) per 1,000 individuals.

Formula:

Example:

If a country has 50,000 deaths in a year and a mid-year population of 5,000,000: CDR=?

Limitations:

• Doesn’t account for age structure of the population.
• Can be misleading when comparing countries with different age demographics.

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2. Age-Specific Death Rate (ASDR)

Definition:

ASDR measures the death rate within a specific age group per 1,000 people in that group.

Formula:

Example:

If there are 500 deaths among people aged 65–74 and that group’s population is 50,000: ASDR=?

Use:

• Helps identify high-risk age groups.
• More accurate than crude death rate for health planning and analysis.

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3. Infant Mortality Rate (IMR)

Definition:

IMR refers to the number of deaths of infants under 1 year of age per 1,000 live births in a given year.

Formula:

Example:

If 1,200 infants die in a year and there were 100,000 live births: IMR=?

Importance:

• Reflects health care quality, nutrition, and maternal health.
• A key indicator of social and economic development.

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4. Neonatal Mortality Rate (NMR)

Definition:

The NMR refers to the number of deaths of infants within the first 28 days of life per 1,000 live births.

Formula:

Example:

If there are 600 deaths within 28 days among 100,000 live births: NMR=?

Use:

• Assesses quality of prenatal and immediate postnatal care.

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5. Adjusted or Standardized Death Rate (SDR)

Definition:

Standardized death rate adjusts the crude death rate to eliminate the effects of differences in age distribution. It allows comparison between populations with different age structures.

Why Standardize?

Populations with more elderly people will naturally have higher crude death rates, even if the healthcare system is good. Standardization accounts for this.

Methods of Standardization:

Two common methods:

• Direct standardization
• Indirect standardization

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A. Direct Standardization

Formula:

Steps:

1. Multiply each age-specific death rate by the standard population for that age group.
2. Sum all the products.
3. Divide by the total standard population.

Use:

• For comparing mortality between countries or over time using a common standard.

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B. Indirect Standardization (Often used when age-specific rates are not available)

Steps:

1. Use standard population’s age-specific death rates.
2. Apply them to your study population to find expected deaths.
3. Compare observed vs. expected deaths.

Standardized Mortality Ratio (SMR):

• SMR = 100: mortality is equal to standard.
• SMR > 100: higher mortality than standard.
• SMR < 100: lower mortality than standard.

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Summary Table:

Measure	Formula	Denominator	Use/Significance
Crude Death Rate (CDR)		Entire population	General mortality level
Age-Specific Death Rate		Age group population	Risk in specific age groups
Infant Mortality Rate (IMR)		Live births	Maternal/child health indicator
Neonatal Mortality Rate		Live births	Immediate newborn care indicator
Standardized Death Rate		Standard population	Removes age structure bias in comparisons

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