Age and sex distribution

The age distribution of persisting cases of SCI from traumatic causes is presented in Figure 3. No adjustment was made for the 12 missing cases here, nor subsequently in the report, as the interest centred not on the absolute value of the incidence rate or case number, but in its change across age and other parameters. The age group of 0 to 14 years was excluded from the figure because of a suspected poor coverage of this group by SUs. Most of these cases would be treated at paediatric hospitals and would be small in number.

Figure 3: Incidence of persisting SCI from traumatic causes by age group, Australia 1996/97 (counts and age specific rates)

• The highest case count, and age specific rate, occurred in the age group 15-24 years. This group accounted for 28 per cent of the persisting cases of SCI from traumatic causes.
• With increasing age, the age specific rate declined to the age group 55-64 years, after which it increased.
• The pattern in the age specific incidence rates of the elderly cases in 1996/97 differed from those reported in 1995/96. In 1996/97 the rate increased from the age group '65-74' to '75 plus', whereas in 1995/96 there was a sharp decline. The 95% confidence intervals on the rates, based on the Poisson distribution, for 1995/96 and 1996/97 indicated that the rate difference for the '75 plus' age group was not significant (not likely to have been affected by the missing cases for 1996/97 referred to earlier). Comparison of the characteristics of the cases in this age group indicated that, whereas in 1995/96 all except one of the seven cases was a fall and none was a motor vehicle occupant, in 1996/97, six of the fourteen cases was a motor vehicle occupant (five were drivers) and the remainder were falls. The apparent variation in the aetiological factors of SCI in this age group is difficult to interpret.
• There was a statistically significant difference in the rates between the age group 15-24 and each of the ten-year age groups from 35-64 years. None of the other apparent differences in the rates between age groups evident in the figure were statistically significant.

Of the persisting cases of SCI from traumatic causes, 80 per cent were male and 20 per cent were female. The incidence of persisting SCI by age group and sex, presented in Figure 4, shows the following: A higher rate of SCI for males at all ages except for the 55-64 year age group (statistically significant). A substantial sex difference in a number of age groups. The male to female rate ratios ranged from a low of 1.3:1 (in the age group 55-64 years) to a high of 7.7:1 (in the age group 65-74 years).

Figure 4: Incidence of persisting SCI from traumatic causes by age group and sex, Australia 1996/97 (age specific rates)