Standardization of Death Rates • • Adjusted or standardized rates: – While comparison of death rates of two populations, ‘crude death rate is not the right yardstick’, as age-compositions are differentQ – Age-adjustment or age-standardization removes confounding effect of different age structures – Standardization may be direct or indirect – Standardization is carried out beginning by using a ‘Standard Population’ Standard population: Is a population where numbers in each age and sex group are known – - – Two frequently used standard populations are: Segi world population - - European standard population Choice of standard population is arbitrary:Q Available standard populations may be used - Standard population may also be created using 2 populations - National population need not always be taken as Standard population - Is commonly used in occupational studies: Comparison of mortality in an industry and general population - Can be used for occurrence of disease (rather than death) Types of Standardized Death Rates • Direct standardization: – Method: - Age-specific rates of the population (whose crude death rate is to be standardized) is applied on a standard population - Total expected deaths calculated - Total expected deaths divided by total standard population to yield stand- ardized death rate – Feasibility: - Availability of age-specific death rates (ASDRQ) - Availability of population in each age group I National population need not always be taken as Standard population I Direct standardization: Feasibility: Availability of age-specific death rates (ASDRQ) mebooksfree.com Direct Standardization Indirect Standardization Method Use actual ASDRs* on the standard age structure Use standard ASDRs* on the actual age structures No. of deaths in each age group Population in each age group Both are available Both are unavailable • Indirect standardization: Standardized mortality ratio (SMR): Is simplest and most useful form – Method: Calculate expected deaths, assuming that study group experiences the death rates of a standard population – Feasibility: Permits adjustment where age-specific rates are not available or are unstable because of small numbers – Examples of indirect StandardizationQ: - Standardized mortality ratio (SMR)Q: SMR = Observed deaths/ Expected deaths × 100 - - - – Life Table Analysis Survival Analysis Regression Analysis Multivariate Analysis