What is the difference between statistical age standardisation and age-gender standardisation?

Whereas age-standardization adjusts for underlying differences in the age distribution of the combined male-female population, age/sex-standardized rates adjust for differences in the population distribution by both age and sex simultaneously.

Age/sex-standardized rates are NOT the same as sex-specific age-adjusted rates.

Like age, sex has a powerful influence on disease rates. Males and females have markedly different incidence, prevalence, and mortality rates for certain diseases and males have a shorter life expectancy than females.

Therefore, in order to fully account for these differences, researchers may want to adjust for both age and sex when making comparisons for some conditions.

The calculation for age/sex adjustment differs from age-standardization in that the individual age-specific rates are stratified by sex and are applied to the standard population stratified by sex.

The requirements for the calculation of age/sex standardized rates are:

• Study population by age and sex

• Standard population by age and sex

• Number of events for males and females in the study population

Formula

ei(f) is the number of events for females in age group i

ei(m) is the number of events for males in age group i

pi(f) is the number of females in age group i the study population

pi(m) is the number of males in age group i the study population

Pi(f) is the number of females in age group i in the Standard population

Pi(m) is the number of males in age group i in the Standard population

For each age stratum the expected number of events is the sum of the expected number of events for males plus the expected number of events for females in that stratum

Age-specific expected events= Ei

=[(ei(m) /pi(m) ) *Pi(m) ] + [ (ei(f) /pi(f) ) *Pi(f) ]

The age/sex Standardized Rate (per 100 000) is the sum of all expected events divided by the total standard population

= [ Sum(Ei)/Sum(Pi)] * 1000