In this study, we aimed to understand how the severity of disability (i.e., no, minimal, mild, and moderate/severe disability and/or limitation) is associated with changes in PA and PI levels from adolescence through young adulthood after controlling for multiple demographic and socioeconomic variables. In the results, we first report descriptive summaries of the subjects’ physical disabilities and/or limitations, demographic and socioeconomic variables, and PA and PI engagement levels. We then show the associations between changes in PA/PI levels and multiple demographic and socioeconomic variables. Finally, we exhibit how physical disability and/or limitation status influences changes in PA and PI levels between adolescence and young adulthood.
3.1 Descriptive summary
Table 1 summarizes the physical disabilities and limitations of adolescent respondents in Wave 1. We categorized the study participants into four levels by disability severity: no, minimal, mild, and moderate/severe disability and/or limitation. Among 15,701 subjects, there were 14,783 respondents without disabilities (94%), 517 adolescents with a minimal level of disability (3%), 185 adolescents with a mild level of disability (1%), and 216 adolescents with a moderate/severe level of disability (1%). Overall, individuals with disabilities (i.e., In-Home Questionnaire) themselves were more likely than their parents to report that they had limb difficulties, used equipment for their conditions, and needed aides for daily activities (i.e., Parent Survey). However, individuals with disabilities were less likely than their parents to answer that they or others considered themselves to have a disability. This gap decreased as disability severity increased. For example, while the same number (n=83) of individuals with more moderate/severe disability and their parents reported that they considered themselves or their children as disabled, only 5 out of the 517 people with minimal disability and 23 out of the 517 parents answered that they or their child had a disability.
Among individuals with minimal disability (n = 517), the majority thought that they had limb difficulties (177, 34%) and used equipment for their conditions (259, 50%). On the other hand, very few people answered that they needed aides for daily activities (3 people), considered themselves disabled (5 people), and had difficulties walking, standing, holding, and grasping (20 people). There were no subjects with more than 3 body parts affected, blindness, or deafness. For people with mild disability, a higher proportion reported that they had any types of difficulties compared to individuals with minimal disability. Out of 185 people, 119 (64%), 97 (52%), and 46 (25%) responded that they had limb difficulties, used equipment for their conditions, and had difficulties walking, standing, holding, and grasping, respectively. Only a limited number of people considered themselves disabled (14 people). There were no people with blindness or deafness in this category. For individuals with moderate/severe disability (n = 216), 140 (65%), 114 (53%), 101 (47%), and 83 (38%) reported that they had limb difficulties, used equipment for their conditions, had difficulties walking, standing, holding, and grasping, and considered themselves disabled. Unlike the other categories, there were people with blindness (one eye: 16; both eyes: 3) and deafness (23 people) in this category.
Table 1. Descriptive summary of physical disabilities and/or limitations in Wave 1
|
No
|
Minimal
|
Mild
|
Moderate/Severe
|
Total (N)
|
14,783
|
517
|
185
|
216
|
Limb difficulties (In-Home Questionnaire / Parent Survey)
|
0 / 0
|
177 / 46
|
119 / 70
|
140 / 99
|
Use equipment for conditions (In-Home Questionnaire / Parent Survey)
|
0 / 0
|
259 / 0
|
97 / 18
|
114 / 51
|
Need aids for daily activities (In-Home Questionnaire / Parent Survey)
|
0 / 0
|
3 / 0
|
3 / 0
|
33 / 14
|
Self/Others consider disabled (In-Home Questionnaire / Parent Survey)
|
0 / 0
|
5 / 23
|
14 / 33
|
83 / 83
|
Difficulties in walking, standing, holding, grasping (In-Home Questionnaire)
|
0
|
20
|
46
|
101
|
More than 3 body parts affected (Parent Survey)
|
0
|
0
|
11
|
58
|
Blindness (one eye / both eyes)
|
0 / 0
|
0 / 0
|
0 / 0
|
16 / 3
|
Deafness
|
0
|
0
|
0
|
23
|
The subjects’ demographic and socioeconomic information in Wave 4 is summarized in Table 2. This table includes age, race, sex, education level, and income level. Age was consistent across the four disability/limitation statuses, with a mean age of 29 years (range: 28.5-28.9) and a SD of 1.7 years (range: 1.6-1.8). For race and sex, we found a slightly higher percentage of people with disabilities who were White (minimal: 3.6%; mild: 1.4%; moderate/severe: 1.6%) and male (minimal: 3.5%; mild: 1.3%; moderate/severe: 1.3%) compared with their counterparts, but the difference was not large. For education level, people with a high school diploma (minimal: 3.2%; mild: 1.1%; moderate/severe: 1.3%) were less likely to have a disability than those without a high school diploma (minimal: 4.0%; mild: 2.3%; moderate/severe: 2.2%). Similarly, those with high income levels were less likely to have a disability than those with low income levels. This trend was especially evident in the moderate/severe disability category (below/near poverty level: 2.6%; low income: 1.6%; middle income: 1.0%; high income: 0.7%).
Table 2. Descriptive summary of demographic and socioeconomic variables by physical disability and/or limitation in Wave 4
Variables
|
Sub-variables
|
Total
|
No
|
Minimal
|
Mild
|
Moderate/
Severe
|
Total (N)
|
Population (count)
|
15,701
|
14,783
|
517
|
185
|
216
|
Age
|
Mean (year)
|
-
|
28.5
|
28.5
|
28.8
|
28.9
|
Max (year)
|
-
|
34
|
33
|
33
|
33
|
Min (year)
|
-
|
24
|
24
|
25
|
25
|
SD (year)
|
-
|
1.8
|
1.7
|
1.6
|
1.6
|
Race
|
White (%)
|
10,945 (100)
|
10,231 (93.5)
|
393 (3.6)
|
149 (1.4)
|
172 (1.6)
|
Black (%)
|
3,620 (100)
|
3,461(95.6)
|
95(2.6)
|
27 (0.7)
|
37 (1.0)
|
American Indian or Alaska Native (%)
|
155 (100)
|
148 (95.5)
|
5 (3.2)
|
2 (1.3)
|
0 (0.0)
|
Asian or Pacific Islander (%)
|
953 (100)
|
917 (96.2)
|
22 (2.3)
|
7 (0.7)
|
7 (0.7)
|
Sex
|
Male (%)
|
7,349 (100)
|
6,897 (93.8)
|
259 (3.5)
|
95 (1.3)
|
98 (1.3)
|
Female (%)
|
8,352 (100)
|
7,886 (94.4)
|
258 (3.1)
|
90 (1.1)
|
118 (1.4)
|
Education
|
High school diploma (%)
|
14,675 (100)
|
13,845 (94.3)
|
475 (3.2)
|
161 (1.1)
|
194 (1.3)
|
No high school diploma (%)
|
1,021 (100)
|
935 (91.6)
|
41 (4.0)
|
23 (2.3)
|
22 (2.2)
|
Income
|
Below/near poverty level (less than $20K) (%)
|
1,756 (100)
|
1,632 (92.9)
|
57 (3.2)
|
21 (1.2)
|
46 (2.6)
|
Low income ($20K–50K) (%)
|
4,801 (100)
|
4,491 (93.5)
|
167 (3.5)
|
67 (1.4)
|
76 (1.6)
|
Middle income ($5K–150K) (%)
|
7,349 (100)
|
6,965 (94.8)
|
237 (3.2)
|
72 (1.0)
|
75 (1.0)
|
High income (>$150K) (%)
|
756 (100)
|
723 (95.6)
|
18 (2.4)
|
10 (1.3)
|
5 (0.7)
|
Table 3 shows the PA and PI levels of the adolescents (Wave 1) and young adults (Wave 4). In Wave 1, the mean PA level was approximately 3.5 times per week (range: 3.4-3.8) with a SD of 2.1 (range: 2.0-2.1) across the four levels of disability categories. On the other hand, the mean PI level was larger than the mean PA level, showing a mean of approximately 22.0 hours per week (range: 20.9-23.0) with a SD of approximately 22.0 (range: 17.9-22.7). In Wave 4, no large difference was found for the mean PA level (range: 3.4-4.0) except for increases in the maximum values (range: 16.0-21.0). Even though the two survey datasets used different survey questionnaires for PI, we consistently observed decreases in the mean PI level (range: 15.4-19.3). For the differences between Wave 4 and Wave 1, we observed consistent decreases in PA sessions per week ranging from -4.1 to -6.8, while no large change was found from the mean PI hours per week (range: -0.2-0.4) regardless of disability level.
Table 3. Descriptive summary of the physical activity and physical inactivity levels in Waves 1 and 4 by physical disability and/or limitation
Wave 1
|
|
No
|
Minimal
|
Mild
|
Moderate/Severe
|
Physical activity (times per week)
|
Mean
|
3.6
|
3.8
|
3.6
|
3.4
|
Max
|
9.0
|
9.0
|
8.0
|
9.0
|
Min
|
0.0
|
0.0
|
0.0
|
0.0
|
SD
|
2.1
|
2.1
|
2.1
|
2.0
|
Physical inactivity (hours per week)
|
Mean
|
23.0
|
22.5
|
20.9
|
23.5
|
Max
|
282.0
|
200.0
|
159.0
|
110.0
|
Min
|
0.0
|
0.0
|
0.0
|
0.0
|
SD
|
21.6
|
22.7
|
22.1
|
17.9
|
Wave 4
|
|
|
|
|
|
Physical activity (times per week)
|
Mean
|
3.6
|
3.6
|
4.0
|
3.4
|
Max
|
21.0
|
17.0
|
16.0
|
17.0
|
Min
|
0.0
|
0.0
|
0.0
|
0.0
|
SD
|
3.1
|
3.0
|
3.5
|
3.1
|
Physical inactivity (hours per week)
|
Mean
|
16.2
|
17.5
|
15.4
|
19.3
|
Max
|
198.0
|
160.0
|
124.0
|
126.0
|
Min
|
0.0
|
0.0
|
0.0
|
0.0
|
SD
|
16.4
|
18.3
|
15.9
|
20.3
|
Differences between Wave 4 and Wave 1 (Wave 4 - Wave 1)
|
Physical activity (times per week)
|
Mean
|
-6.8
|
-4.8
|
-5.3
|
-4.1
|
Max
|
195
|
112
|
121
|
116
|
Min
|
-268
|
-190
|
-152
|
-86
|
SD
|
24.7
|
25.8
|
25.3
|
25.6
|
Physical inactivity (hours per week)
|
Mean
|
-0.0
|
-0.2
|
0.4
|
-0.0
|
Max
|
18
|
13
|
12
|
15
|
Min
|
-9
|
-9
|
-8
|
-6
|
SD
|
3.4
|
3.4
|
3.6
|
3.1
|
3.2 Associations between changes in PA/PI levels and demographic/socioeconomic variables
Here, we enumerate several statistically significant associations between changes in PA/PI levels and multiple demographic and socioeconomic variables and disability severity. Table 4 exhibits the RRR and p values of each variable in the model.
Table 4. Multinomial logistic regression on changes in PA and PI levels by race, income level, education level, sex, age, and physical disability and/or limitation. Relative risk ratios and p values are shown in parentheses.
|
|
PA difference
(Ref: No change)
|
PI difference
(Ref: No change)
|
Variables
|
Category/units
|
More decreased
|
Decreased
|
Increased
|
More increased
|
More decreased
|
Decreased
|
Increased
|
More increased
|
Race
(Ref: White)
|
African American
|
0.83 (0.27)
|
1.07 (0.27)
|
0.97 (0.67)
|
1.05 (0.67)
|
4.08 (0.00)
***
|
2.37 (0.00)
***
|
1.35 (0.00)
***
|
1.90 (0.00)
***
|
American Indian or Alaska Native
|
1.44 (0.54)
|
0.82 (0.50)
|
0.95 (0.86)
|
1.61 (0.18)
|
3.77 (0.00)
***
|
1.72 (0.08)
*
|
1.37 (0.35)
|
2.43 (0.06)
*
|
Asian or Pacific Islander
|
0.66 (0.22)
|
1.12 (0.31)
|
1.03 (0.77)
|
1.29 (0.12)
|
0.62 (0.15)
|
1.24 (0.13)
|
1.24 (0.13)
|
1.19 (0.53)
|
Income
(Ref: Below or near poverty level)
|
Low
|
0.80 (0.32)
|
1.09 (0.35)
|
1.10 (0.35)
|
0.82 (0.17)
|
0.77 (0.07)
*
|
0.82 (0.05)
**
|
0.74 (0.00)
***
|
0.57 (0.00)
***
|
Middle
|
0.86 (0.50)
|
0.96 (0.68)
|
1.15 (0.16)
|
0.85 (0.23)
|
0.64 (0.00)
***
|
0.66 (0.00)
***
|
0.57 (0.00)
***
|
0.35 (0.00)
***
|
High
|
1.69 (0.08)
*
|
1.17 (0.25)
|
1.18 (0.27)
|
0.61 (0.05)
*
|
0.37 (0.00)
***
|
0.59 (0.00)
***
|
0.50 (0.00)
***
|
0.33 (0.00)
***
|
Education
(Ref: High school diploma)
|
No high school diploma
|
0.79 (0.36)
|
0.78 (0.01)
***
|
1.14 (0.31)
|
1.07 (0.72)
|
0.76 (0.11)
|
0.91 (0.49)
|
0.86 (0.25)
|
0.58 (0.00)
***
|
Sex
(Ref: Male)
|
Female
|
0.38 (0.00)
***
|
0.65 (0.00)
***
|
0.82 (0.00)
***
|
0.55 (0.00)
***
|
0.48 (0.00)
***
|
0.60 (0.00)
***
|
0.65 (0.00)
***
|
0.59 (0.00)
***
|
Age
|
Continuous data
|
0.72 (0.00)
***
|
0.84 (0.00)
***
|
1.06 (0.00)
***
|
1.11 (0.00)
***
|
0.85 (0.00)
***
|
0.89 (0.00)
***
|
1.05 (0.02)
**
|
0.98 (0.46)
|
Disability
(Ref: No disability)
|
Minimal
|
0.96 (0.92)
|
1.29 (0.05)
**
|
0.81 (0.23)
|
0.87 (0.59)
|
0.86 (0.61)
|
0.69 (0.08)
*
|
0.96 (0.83)
|
1.31 (0.37)
|
Mild
|
2.09 (0.11)
|
0.91 (0.71)
|
0.89 (0.66)
|
1.55 (0.17)
|
0.75 (0.58)
|
0.54 (0.12)
|
0.87 (0.67)
|
0.85 (0.78)
|
Moderate/Severe
|
0.00 (0.00)
***
|
0.80 (0.35)
|
0.69 (0.17)
|
0.86 (0.69)
|
0.89 (0.80)
|
1.54 (0.07)
*
|
0.95 (0.86)
|
2.25 (0.02)
**
|
3.2.1 Race
Even though we were not able to observe any significant relationships between PA differences (Wave 4 - Wave 1) and race at the 95% significance level, African American and American Indian or Alaskan Native individuals had a significant relationship with PI differences. In detail, African Americans were more likely to increase (Increased: RRR = 1.35, p value = 0.00; Substantially increased: RRR = 1.90, p value = 0.00) or decrease (Decreased: RRR = 2.37, p value = 0.00; More decreased: RRR = 4.08, p value = 0.00) than maintain their PI levels compared to White individuals. On the other hand, American Indian or Alaskan Native individuals were more likely to decrease (more decreased: RRR = 3.77, p value = 0.00) than maintain their PI levels compared with White individuals.
3.2.2 Income
Income was also one of the important factors deciding PA and PI patterns over the life course. For the PA difference, although not statistically significant at the 95% significance level, we found that all income groups were more likely to increase (Low income: RRR = 1.10, p value = 0.35; Middle income: RRR = 1.15, p value = 0.16; High income: RRR = 1.18, p value = 0.27) their PA levels than maintain their PA levels compared with the group below or near the poverty level. However, we also found that the group below or near the poverty level was more likely to be classified in the “Substantially increased” category (Low income: RRR = 0.82, p value = 0.17; Middle income: RRR = 0.85, p value = 0.23; High income: RRR = 0.61, p value = 0.05). In other words, all income groups tended to increase their PA levels to a certain level and then decrease their PA levels compared to the group below or near the poverty level.
On the other hand, for the PI difference, we found that low-income (Increased: RRR = 0.74, p value = 0.00; Substantially increased: RRR = 0.57, p value = 0.00) groups were less likely to increase than maintain their PI levels compared to the group below or near the poverty level. Interestingly, the middle- (Substantially decreased: RRR = 0.64, p value = 0.00; Decreased: RRR = 0.66, p value = 0.00; Increased: RRR = 0.57, p value = 0.00; Substantially increased: RRR = 0.35, p value = 0.00) and high-income (Substantially decreased: RRR = 0.37, p value = 0.00; Decreased: RRR = 0.59, p value = 0.00; Increased: RRR = 0.50, p value = 0.00; Substantially increased: RRR = 0.33, p value = 0.00) groups were more likely to maintain their PI levels than to decrease or increase their PI levels compared to the group below or near the poverty level.
3.2.3 Education
Individuals without high school diplomas were 0.78 times less likely to decrease their PA levels than maintain their PA levels compared to those with high school diplomas. Although not statistically significant, we found that people without high school diplomas were less likely to decrease their PA levels (Substantially decreased: RRR = 0.79, p value = 0.36; Decreased: RRR = 0.78, p value = 0.01) and more likely to increase their PA time (Increased: RRR = 1.14, p value = 0.31; Substantially increased: RRR = 1.07, p value = 0.72) than maintain their PA levels compared to those with high school diplomas. On the other hand, for PI, we found that those without high school diplomas were less likely to increase their PI levels (Substantially increased: RRR = 0.58, p value = 0.00) than maintain their PI levels compared to those with high school diplomas.
3.2.4 Sex and age
For sex, we found that females were more likely to maintain their PA (More decreased: RRR = 0.38, p value = 0.00; Decreased: RRR = 0.65, p value = 0.00; Increased: RRR = 0.82, p value = 0.00; Substantially increased: RRR = 0.55, p value = 0.00) and PI levels (More decreased: RRR = 0.48, p value = 0.00; Decreased: RRR = 0.60, p value = 0.00; Increased: RRR = 0.65, p value = 0.00; Substantially increased: RRR = 0.59, p value = 0.00) than to increase or decrease their PA levels compared to males. However, we found a different relationship with age. With increases in age, individuals were less likely to decrease their PA levels (More decreased: RRR = 0.72, p value = 0.00; Decreased: RRR = 0.84, p value = 0.00) and more likely to increase their PA levels (Increased: RRR = 1.06, p value = 0.00; Substantially increased: RRR = 1.11, p value = 0.00) than to maintain their PA levels. Similarly, with increases in age, people were less likely to decrease their PI levels (more decreased: RRR = 0.85, p value = 0.00; decreased: RRR = 0.89, p value = 0.00) and more likely to increase their PI levels (increased: RRR = 1.05, p value = 0.02) than to maintain their PA levels.
3.3 Associations between changes in PA/PI levels and physical disability and/or limitation status
We found that individuals with minimal disabilities were more likely to decrease their PA levels (Decreased: RRR = 1.29; p value = 0.05) than to maintain their PA levels compared to those without disabilities. This suggests that the group with the minimal level of disability was 1.29 times more likely to be in the decreased PA group than in the no difference PA group. For PI, we also found that individuals with moderate/severe disabilities were more likely to increase their PI levels (Substantially increased: RRR = 2.25; p value = 0.02) than maintain their PI levels compared to those without disabilities. This indicates that the group with a moderate/severe level of disability was 2.25 times more likely to belong to the substantially increased PI group than in the no difference PI group. However, no statistically significant impact was found for those with mild levels of disability (reference group: general population) in either PA or PI levels.