Dr Qurat ul ain MBBS , MD , diploma in clinical Research (USA) Mortality Indicators Dr Qurat ul ain MBBS , MD , diploma in clinical Research (USA)
Objectives for the session students should be able to Define mortality indictors Enumerate various mortality indicators Describe some important mortality indicators
Indicator : Indicates a situations Index : plural of indicator Mortality is a term which means “death” or describes death and related issues Indicator : Indicates a situations Index : plural of indicator
Mortality Table
Three Levels of Rates Crude rates Specific rates/ratios Adjusted rates
Crude rates
CRUDE Death Rates “General” (crude) mortality rate a population group exposed to risk of death a time period Crude Mortality Rate = # of deaths occurring in that population during that period of time
Crude Death Rates Does NOT account for differences of age, sex, etc. in any aspect of death Info needed: total deaths total population a given period of time SIMPLEST
Crude Death Rates
Disadvantage Lack of comparability when two vary ( with respect to age , sex , race etc.)
Specific rates used especially when we have to throw light on etiology Specific to a cause eg: specific deaths due to tuberculosis ,,,HIV/AIDS Specific to groups : like age sex , race Advantage : allows comparability
Cause Specific Mortality Rate
Cause Specific Mortality Rate
Case Fatality Rate Killing power of a disease (how fatal a diseases can be ) It ratio of deaths to cases For acute cases Cannot be used for chronic diseases
Case Fatality Rate
Specific Death Rates for different ages For example: infant mortality
Adjusted rates
Adjusted rates are more reliable as they avoid the confounding variables like age and sex etc Most common method of adjustment are Direct standardization Indirect standardization
For standardizing we need to have a standard population who age and sex composition is known Direct standardization is used whenever stable stratum- specific rates are available Indirect standardization is used when stratum-specific rates are unavailable or unstable because of small numbers
Standardization is a method of adjustment Standardization is a method of adjustment. This is generally done for age differentials but can also be done for other factors. The objective is to remove the effect of differential mortality or differential structure of the subgroups in the two populations under comparison. The rates are then brought to a common base and thus made comparable.
Two methods of standardization are in use Two methods of standardization are in use. Both require assumption of a Standard or a reference population. This could be real or hypothetical, but in both cases the standard is arbitrary. In case of age standardization, the standard may have a predefined age structure or a predefined ASDR( age specific death rate). These two methods of standardization can give entirely different results.
Indirect standardization
When stratum-specific numbers are small, stratum-specific rate estimates are too susceptible to being heavily influenced by random variability for the direct standardization method to be satisfactory. Instead, an "indirect" standardization procedure is often used and a "standardized mortality ratio" ("SMR") computed. (The standard mortality difference, computed as the indirectly standardized rate minus the crude rate from the standard population, is also theoretically of interest). Indirect standardization avoids the problem of imprecise estimates of stratum-specific rates in a study population by taking stratum-specific rates from a standard population of sufficient size and relevance.
These rates are then averaged using as weights the stratum sizes of the study population Thus, the procedure is the mirror-image of direct standardization. In direct standardization, the study population provides the rates and the standard population provides the weights In indirect standardization, the standard population provides the rates and the study population provides the weights
Standardized Mortality Ratio (SMR)
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