Table 1 Measures of effect and burden of disease
From: Assessment of public health impact of work-related asthma
Measure and definition | Formula |
|---|---|
Incidence rate ratio = IRR gives an estimate of the risk of developing asthma related to the exposure of interest in comparison to no exposure | IRR = IRe/IR0 where IRe is the incidence rate of asthma among the exposed and IR0 is the incidence rate of asthma among the unexposed |
Attributable fraction = AF estimates the proportion of exposed cases for whom the disease can be attributed to the exposure of interest | AF = (IRR-1)/IRR or AF = (IRe -IR0)/IRe where IRe is the incidence rate of asthma among the exposed and IR0 is the incidence rate of asthma among the unexposed |
Population attributable fraction = PAF gives the reduction in incidence of disease that would be achieved if the population were entirely unexposed | PAF = Pe × AF or PAF = Pe × (IRR-1)/[Pe × (IRR-1) + 1] where Pe is an estimate of the prevalence of the occupational exposure(s) of interest for the population of interest |
Excess burden of disease = EBD gives the excess number of incident cases that can be attributed to the exposure of interest | EBD = PAF × totNi, where PAF is the population attributable fraction due to the occupational exposure(s) of interest and totNi is the total number of incident cases of adult-onset asthma |
Disability adjusted life years = DALY gives the sum of the number of years of life lost due to premature mortality and the number of years of healthy life lost due to disability among incident cases of the health condition | DALY = YLL + YLD where YLL is the years of life lost due to premature mortality and YLD is the years of healthy life lost due to disability |