Age and sex distribution

The age distribution of persisting cases of SCI from traumatic causes is presented in Figure 3. The case counts and rates shown in Figures 3 and 4 are estimates which include the 14 cases whose registration information was missing and whose age and sex distribution was matched to that of the nationally reported cases. 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 1997/98 (counts and age specific rates)

• The highest case count, and age specific rate, occurred in the age group 15-24 years. With increasing age, the age specific rate declined substantially to the age group 45-54 years, after which it increased moderately to age group 65-74 years and then decreased moderately beyond this age group. The most substantial decline in the case count and rate occurred from age group 35-44 years to 45-54 years.
• The wide confidence intervals on the rates (95% confidence intervals on the rates, based on the Poisson distribution) reflect the small case count for individual age groups. When age groups 15-24 years, 25-34 years and 35-44 years were combined it was evident that the rate for this group (23.1 per million of population) was significantly higher, statistically, than the rate for the older combined age group of 45 years and above (12.4 per million of population).

Of the persisting cases of SCI from traumatic causes aged 15 years and above, 79 per cent were male and 21 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 1.8:1 (in the age group 75 plus) to a high of 6.8:1 (in the age group 25-34 years).

Figure 4: Incidence of persisting SCI from traumatic causes by age group and sex, Australia 1997/98 (age specific rates)

When compared to 1995/96 and 1996/97 a number of differences in the age/sex distribution in 1997/98 were noted:

• The female rate of SCI in the age group 15-24 years increased relative to the male rate. Whilst the difference in the rates of males and females in this age group in 1997/98 was large, it was not statistically significant.
• There was a substantial increase in the male rate for the age groups 25-34 years and 35-44 years primarily due to a doubling in the cases in this age group in Western Australia.