Figure 2-7 displays the age-specific prevalence rates for any activity limitation designated according to these five groups of causes. Figure 2-8 shows the proportion of activity limitation in each age group ascribed to each of these groups of conditions.
Figures 2-7 and 2-8 show that the main causes of activity limitation vary markedly with age. In children under 18, intellectual limitations (two-thirds of which are mental retardation and one-third mental illness) account for 27 percent and chronic diseases (two-thirds of which are asthma) account for 26 percent of all activity limitations. Sensory limitations, especially visual and hearing, also account for a relatively high fraction (16 percent), followed by mobility limitations (14 percent).
Above age 18 mobility impairments become more prevalent and are the leading major cause of activity limitation for all adult age groups. The prevalence of activity limitation caused mainly by mobility impairments increases from 40.5 per 1,000 at ages 18-44 to 188.4 per 1,000 at ages 85 and above. The components of this group change by age, however. For ages 18-44, back/spine injuries dominate at 48 percent, followed by orthopedic impairments at 29 percent. Arthritis accounts for 11 percent of the