Racial/Ethnic Composition of the SPORT population
The SPORT population includes 2,011 (86.5%) Whites, 182 (7.8%) Blacks, and 130 (5.6%) Others (50 Hispanic/Latino, 11 American Indian/Alaska Native, 25 Asian, 6 Native Hawaiian/Pacific Islander, 38 More Than One Race). The SPORT population () has a smaller proportion of Blacks (6.13% IDH/ 9.57% SpS/DS) compared to that of the Hospital Referral Regions (HRRs) from which SPORT patients are drawn (17.8%) or the U.S. population as a whole (12.3%). The proportion of patients in the Other category (6.13% IDH/ 5.13% SpS/DS) is slightly higher than that of the hospital referral population (4.7%) but considerably lower than that of the U.S. population as a whole (12.6%).
Characteristics at Baseline
The demographic and medical history characteristics of the SPORT population are compared among the three racial groups in . Age, sex, BMI, education, income, marital status, and work/legal status were significantly associated with racial group. Mean age was lower (p=0.014) for Others (49 years) compared to Whites and Blacks (both 54 years). A greater proportion of Blacks were male (36.8%) than among Whites (52.8%) and Others (51.5%, p<0.001). Median BMI was higher (p<0.001) among Blacks (28.8) and Others (27.4) than among Whites (26.8). Blacks were less likely to have a college or graduate degree (Black: 60.2%, White: 70.6%, Other: 70.0%, p=0.014), more likely to have no job (Black: 40.7%, White: 34.5%, Other: 34.6%) and more likely to earn less than $20,000 per year if they did have a job than Whites and Others (Black: 24.2%, White: 16.2%, Other: 13.8%, p<0.001). Black subjects were more likely (p<0.001) to report having hypertension (51.8%) compared to Whites (28.6%) and Others (24.6%) and were more likely (p<0.001) to report having diabetes (17.0%) than Whites (8.2%) or Others (10.0%). Blacks were also more likely (p=0.039) to have joint problems (46.2%) than Whites (36.6%) and Others (34.6%). Other subjects were more likely (p=0.024) to report stomach problems (25.4%) than either Whites (16.6%) or Blacks (19.8%).
Patient Characteristics by Racial Group
Diagnosis and quality of life characteristics are compared among the racial groups in . There were significant differences in diagnosis among the racial/ethnic categories, with 50.8% of Whites diagnosed with IDH, 25.5% with SpS, and 23.8% with DS compared to 39.0% IDH, 29.1% SpS, 31.9% DS for Blacks, and 54.6% IDH, 27.7% SpS, 17.7% DS for Others (p=0.011). Back symptoms were less bothersome (p=0.001) and less frequent (p<0.001) among White subjects compared to Blacks and Others (p=0.001). Whites had higher median SF-36 physical (p=0.001) and mental (p=0.001) component summary scores and lower median ODI scores (P=0.016) than Blacks or Others. (NOTE: The lower score on ODI indicates less disability, whereas a higher score on the SF-36 means less pain, less mental distress, etc).
Having a Worker’s Compensation claim, time since quitting smoking, history of stroke, osteoporosis, cancer, fibromyalgia, migraine headaches, chronic fatigue syndrome, depression, anxiety/panic disorder, PTSD, alcoholism, drug dependency, heart problems, lung problems, stomach problems, bowel/intestinal problems, liver problems, kidney problems, blood vessel problems, nervous system problems and duration of low back/leg pain were not significantly associated with racial groups.
In univariate analyses (), treatment preferences varied significantly among the racial groups overall (p=0.008). Blacks were less likely to prefer surgical treatment (33.0%) compared to Whites (46.6%) and Others (43.8%). These relationships persisted within each of the diagnosis groups but were less statistically significant. Overall, Others were the group most willing to be randomized (47.7%) compared to Whites (42.9%) and Blacks (45.1%) but this difference was not statistically significant (p=0.50). Among patients diagnosed with SpS/DS, Others were the group most willing to be randomized (54.2%) compared to Whites (46.6%) and Blacks (42.3%), while among patients diagnosed with IDH, Black subjects were more willing (49.3%) to be randomized than Whites (39.3%) or Others (42.3%). None of these differences reached statistical significance.
Univariate Analysis of Treatment Preferences and Willingness to be Randomized Rates by Diagnosis and Racial Group
Treatment preferences adjusted for baseline differences are compared among the racial groups. Black subjects were less likely than Whites or Others to prefer surgical treatment among both IDH (White=51.0%, Black=35.2%, Other=47.9%,) and SpS/DS (White=42.1%, Black=31.5%, Other=39.0%,) patients () We also examined factors which influenced treatment preferences within diagnosis among the racial groups. In adjusted analyses, significant differences between the racial groups were observed for the following factors: Among the IDH patients ability to enjoy usual leisure activities (White=48.0%, Black=33.6%, Other=36.2%, p=0.027); worries about money (White=6.6%, Black=13.2%, Other=1.4%, p=0.007); and risks of surgery (White=23.4%, Black=33.1%, Other=39.0%, p=0.010). For SpS/DS patients, advice or experience of friends (White=5.2%, Black=12.7%, Other=10.5%, p=0.047); ability to work (White=72.2%, Black=60.5%, Other=62.6%, p=0.035); ability to enjoy usual leisure activities (White=53.9%, Black=41.6%, Other=31.4%, p=0.007) ; risk of surgery (White=29.1%, Black=41.7%, Other=37.3%, p=0.034; and non-operative treatment being ineffective (White=25.9%, Black=15.6%, Other=21.1%, p=0.058) varied significantly among the racial groups.
Willingness to be Randomized
The results of multivariate analyses designed to assess the independent effects of race and treatment preference on willingness to be randomized while controlling for baseline differences among the race groups is shown in . In this analysis, race was no longer a significant predictor of willingness to randomize in either IDH (OR=1.13 for Blacks compared to Whites, p=0.66; OR=1.02 for Others, p=0.95) or SpS/DS (OR=0.71 for Blacks, p=0.16; OR=1.44 for Others, p=0.24) patients. Treatment preference remained a significant, strong predictor of willingness to randomize in both diagnostic groups. Compared to patients with a baseline preference for non-operative treatment, those who were unsure were much more likely (OR=3.60 for IDH, p<0.001; OR=5.31 for SpS/DS, p<0.001) to agree to be randomized. Those who preferred surgical treatment were much less likely (OR=0.25 for IDH, p<0.001; OR=0.40 for SpS/DS, p<0.001) to agree to be randomized compared to those who preferred non-operative treatment.
Willingness to be Randomized (Adjusted Odds Ratios) by Racial Group and Treatment Preference at Baseline