CALCULATION OF THE INDIRECT COSTS OF ASTHMA

2.1 Absenteeism

The total cost of asthma related absenteeism includes the cost of adults missing a day of work due to illness and the cost of a caregiver having to miss work to care for a sick asthmatic child. The total annual cost to the Australian community of asthma related absenteeism for 1991 is estimated to be in the range of $200 to $234 million.

The total cost estimate of direct asthma related absenteeism of over $110 million is based on relatively current usage and cost data. The schemata in Figure One illustrates the calculation.

The ABS 1989/90 National Health Survey is the only available estimate of adult asthma related absenteeism. The survey found that some 20,100 work days were lost due to asthmatic illness in the two week survey period and this forms the basis of the annual volume. It assumes that only employed asthmatics responded to the question referring to asthma related absenteeism.

The value of a single day of absenteeism is estimated on the basis of the 1991 Market Price GDP after adjusting for a typical 230 working days per annum.

Similarly the estimates for the total cost of caregiver absenteeism in the range of $90 to $120 million are compiled from the best available current data. See Figure Two for the detailed calculation.

The volume of schooldays lost annually by asthmatic children was based on the only available figure of 50,800 days in a two-week period from the ABS 1989/90 National Health Survey. Given that not all caregivers are employed outside the home, the total schooldays lost to asthma was adjusted for the percentage of caregivers currently employed. This percentage was based on 1990 ABS labour participation rates for females with dependants. Females were assumed to be the predominant caregivers because of the 1990 ABS finding that 52.9% of married females with dependants are not in the labour force compared with only 5.5% of married males with dependants.

The economic value of a lost day's work was again based on Market Price GDP.

The reliability of the total cost figure, however, can be challenged on the validity of the assumptions equating lost school days to work absenteeism. Some school children would be of an age whereby they could take care of themselves when ill. Similarly some employed caregivers could have relatives or friends who could take care of a sick asthmatic child. Alternatively an employed caregiver may not work full-time and therefore not necessarily lose a day's work for a dependant's asthma.

A sensitivity analysis based on the employment profile of females was performed to take account of the potential impact part-time employment has on the cost of caregiver absenteeism. ABS 1990 data shows that 52.2% of all employed females are employed on a part-time basis. By applying this percentage to the potential volume of schooldays lost, it can be calculated that some 277,000 days apply to part-time employed caregivers and a further 303,000 days to caregivers working full-time. ABS 1990 data on female part-time working hours shows that on average part-time employment is 40.2% of full-time employment hours. If it is assumed that 40.2% of the designated part-time caregiver days actually result in work absenteeism, then this equates to 111,500 days. No adjustment has been made to full-time caregiver absenteeism levels. The lower estimate of the adjustment for part-time caregiver absenteeism is therefore $90 million.

2.2 Lost Productivity at Work

A range of cost estimates for lost productivity at work, ranging from $40 million to $100 million, was developed based on varying assumptions of the impact asthma has on the level of an individual's work effectiveness. This was the best available approach given a lack of accurate objective information on asthma related lost productivity. The cost of lost output due to asthmatics leaving work to attend consultations has been calculated in a separate section.

Figure Three illustrates the calculation. The ABS 1989/90 National Health Survey estimate of total days of reduced work activity was annualised by assuming 230 working days per annum (5 day working week, 20 days annual leave and 10 days of public holidays). The total number of asthma affected work days was reduced by adjusting for the National Health Survey's percentage estimate of employed asthmatics. The potential impact asthma has on productivity levels was accounted for by altering the GDP cost of reduced activity over a range of possible values.

The assumptions chosen for the degree of lost productivity due to asthmatic illness were a 10% and 25% reduction in work effectiveness. The lower estimate equates to about 45 minutes lost output, after excluding meal breaks, in a typical 7.5 hour working day. This does not seem unrealistic if one considers the time it takes to recover from an acute asthmatic attack. The upper estimate represents lost output of 105 minutes on an asthma affected work day which does not seem unreasonable either given the potential handicap severe asthma can impose on a person's lifestyle.

2.3 Travel Time For Treatment

The total annual cost to the community of asthmatics attending both medical and allied health consultations is estimated at between $23 to $64 million for 1991 (see Figure Four for calculation). This is the cost of foregone output from the lost work time an employed asthmatic experiences as a result of travelling to, attending and returning from consultations.

The total consultation volumes have been adjusted for the number of employed asthmatics. (See Medical Consultation section in Appendix One.) It has been assumed that all consultations occur during work hours and that only one hour of productive work time is lost. This latter figure is based on Ross' estimate for the time taken to attend an asthma consultation (Ross, 1985). It should be reviewed in the context of the higher estimates of work time lost to attend consultations for other diseases (eg. the estimate of 1.5 hours by Worthington di Marzio) and in the light of these, appears conservative. The lost output has been valued at the hourly GDP rate of $28.40.

By challenging the assumption that all consultations occur in working hours, a much lower cost estimate is achieved for lost output due to employed asthmatics attending consultations. Specialist consultations are most likely to occur in normal working hours and these constitute 15% of all consultations. If one assumes that a quarter of all other consultations, (GP and allied health consultations) are in working hours, the potential volume of consultations affecting work productivity falls to 815,625. This figure is reasonable given the fact that some GPs do not offer out-of-hours service and that some medical consultations for acute exacerbations of asthma will inevitably coincide with a day of absenteeism.

A mid-range estimate of $42 million is calculated if one maintains the assumption that all specialist consultations and 60% of GP and allied health consultations occur during working hours.

Content Updated 1992