Data issues

• Data sources
• Case definition

Data sources

Deaths data are from the Australian Bureau of Statistics (ABS) mortality unit record data collection, 1979-98. Hospital separations data are from hospital separations unit record data collection, 1996-97 and are provided by the AIHW. Population data were obtained from the ABS and are based on ABS estimates of resident population as at 30 June 1998. Estimated number of horse riders engaged in sport and recreational activities during 1997 were obtained from the ABS (Australian Bureau of Statistics 1999).

Case definition

Death data

The cause of each death registered in Australia is classified by the ABS according to the International Classification of Diseases (ICD). The 9th revision (ICD9) has been used for death registrations beginning in 1979. All deaths given an ICD9 "External Cause" code by the ABS are included in the mortality dataset.

Data are presented according to the year in which deaths were registered. For deaths occurring in the latter part of the calendar year, registration may not occur until the following year. For the year 1998, seven per cent of the death registrations in the 1998 mortality dataset included deaths that occurred in previous years.
State-specific data are presented on the basis of the state or territory in which death was registered. This is normally the one in which death occurred.

Hospital separations data

Unit record hospital separations data relating to injury and poisoning were obtained from the Australian Institute of Health and Welfare (AIHW). Selection criteria for these cases were as follows:

1. An ICD9-CM External cause E-code in the external cause field; and
2. An ICD9-CM Principal Diagnosis code in the range 800.00-999.99 (Chapter 17 `Injury and Poisoning').

Selection of horse-related hospital separations

Horse-related hospital separations were obtained from the hospital separations 1996-97 dataset as specified above by selecting cases where the main E-code had one of the values in Table A.

Estimation of incident cases

The main matter of interest for this report is the incidence of horse-related injury resulting in death or admission to a hospital. The hospital data count episodes of inpatient care. Some injuries result in more than one episode of care at one or more hospitals. One aid to identifying cases likely to have resulted in more than one episode is the data item `Mode of Separation'. For present purposes, cases discharged to another acute hospital, and `statistical' discharges have been omitted from estimates of incident case numbers. The bed-days occupied by these cases have been included in estimates of the burden of injury.
Incident cases were estimated by excluding unit records that had the following modes of separation:

1. Discharge/transfer to an(other) hospital
2. Statistical discharge - type change
3. Statistical discharge from leave

Age adjustment

Some all-ages rates have been standardised to overcome the effect of differences in the proportions of people of different ages (and different injury risks) in the populations that are compared. Direct standardisation was employed, taking the Australian population in 1991 as the standard.

Time series

Mortality time trends have been presented for the period 1979 to 1998. This is the period during which Australian deaths data have been classified according to the 9th revision of the International Classification of Diseases (ICD9).