We calculated age-standardized ratios (Relative Illness Ratio and Relative Mortality Ratio) in order to compare the age distribution of morbidity and mortality due to influenza between the two countries and between seasonal influenza epidemic and influenza pandemic.
We first calculated the relative illness ratio (RIR), as the ratio of the percentage of sick persons in a given age group to the percentage of the general population belonging to the same age group.
The ratios were calculated as follows: Relative Illness Ratio (RIR): (Ci/Σ Ci)/(Ni/Σ Ni) Ci: number of cases of influenza-like illness in a given age group Σ Ci: Sum of cases of influenza-like illness in all age groups Ni: Population in a given age group Σ Ni: Sum of populations in all age groups.
DFLE and HLE by age and gender for five-year age groups were computed for 16 ethnic groups by combining the 2001 Census data on ethnicity, self-reported limiting long-term illness and self-rated health using mortality by ethnic group estimated by two methods: the Standardised Illness Ratio (SIR) method and the Geographically Weighted Method (GWM).
The first estimation method, called the Standardised Illness Ratio (SIR) method, used the relationship of standardised mortality ratios (SMRs) and SIRs of the UK LAs, all-group population and sex, to estimate SMRs for the 16 ethnic groups from their SIRs, under the assumption that the all-group relationship applied to each individual ethnic group.
These variables were as follows: standardized limiting long-standing illness ratio (age less than 75 years), standardized mortality ratio (age less than 75 years), proportion of economically active citizens who are unemployed, proportion of pensionable-aged citizens living alone, and proportion of dependents in single-carer households.
At study outset, both areas exhibited high scores on the major deprivation indices including Oxford, Breadline Britain, Townsend, Jarman and Carstairs and with elevated Standard Mortality Rates, Standard Long Term Illness and permanent sickness ratios.
Two national surveys, however, have reported a striking degree of variability between institutions within the same country in terms of referral to physical therapy during critical illness, staff ratios and frequency of such therapy [ 19, 20].
Three of the trials reported a lack of effect for the prevention of acute respiratory illness: risk ratios 0.94 (95% confidence interval 0.66 to 2.43), 24 0.97 (0.72 to 1.30), 22 and 1.10 (0.97 to 1.24).
The ratio of the human infected to ill ratio indicating number of asymptomatic infections to symptomatic infections decreases as the probability of illness increases.
