Table 4. Factors associated with mitochondrial copy number among African American SAPPHIRE participants.
| Variable | Univariable Analysis | Model 1† | Model 2‡ | Model 3§ | Model 4|| | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| R2* | Unadjusted parameter estimate | P-value | Adjusted parameter estimate | P-value | Adjusted parameter estimate | P-value | Adjusted parameter estimate | P-value | Adjusted parameter estimate | P-value | |
| Asthma status | 0.016 | 18.13 | <0.001 | 19.42 | <0.001 | 34.19 | <0.001 | 18.19 | <0.001 | 33.25 | <0.001 |
| Age (years) | 0.003 | -0.28 | <0.001 | -0.17 | 0.039 | -- | -- | -- | -- | -0.20 | 0.096 |
| Female Sex | <0.001 | 0.17 | 0.937 | 1.68 | 0.447 | -- | -- | -- | -- | -6.54 | 0.048 |
| African Ancestry | 0.003 | 29.64 | <0.001 | 33.97 | <0.001 | -- | -- | -- | -- | 9.44 | 0.483 |
| BMI (kg/m2) | 0.002 | -0.33 | 0.003 | -0.39 | <0.001 | -- | -- | -- | -- | 0.05 | 0.790 |
| Smoking status | <0.001 | 0.36 | 0.879 | -2.93 | 0.219 | -- | -- | -- | -- | 7.00 | 0.058 |
| Percent of predicted FEV1 | <0.001 | -0.04 | 0.452 | 0.05 | 0.383 | -- | -- | -- | -- | -0.09 | 0.253 |
| Total WBC count | 0.133 | -11.70 | <0.001 | -- | -- | -- | -- | -- | -- | -- | -- |
| Neutrophils | 0.120 | -13.79 | <0.001 | -- | -- | -14.58 | <0.001 | -- | -- | -14.36 | <0.001 |
| Monocytes | 0.043 | -87.33 | <0.001 | -- | -- | -13.84 | 0.148 | -- | -- | -18.32 | 0.067 |
| Lymphocytes | 0.033 | -16.62 | <0.001 | -- | -- | -13.14 | <0.001 | -- | -- | -12.67 | <0.001 |
| Eosinophils | 0.003 | -21.91 | 0.013 | -- | -- | -20.21 | 0.014 | -- | -- | -24.34 | 0.004 |
| Platelet count | 0.008 | 0.10 | <0.001 | -- | -- | 0.217 | <0.001 | -- | -- | 0.23 | <0.001 |
| Mitochondrial haplogroup | 0.005 | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| L0 vs West Eurasian | -- | -1.38 | 0.833 | -- | -- | -- | -- | -0.74 | 0.909 | -1.47 | 0.875 |
| L1 vs West Eurasian | -- | 12.58 | 0.014 | -- | -- | -- | -- | 12.98 | 0.010 | 9.47 | 0.218 |
| L2 vs West Eurasian | -- | 8.19 | 0.094 | -- | -- | -- | -- | 8.55 | 0.078 | 6.38 | 0.390 |
| L3 vs West Eurasian | -- | 14.94 | 0.002 | -- | -- | -- | -- | 14.77 | 0.002 | 13.21 | 0.073 |
SAPPHIRE denotes Study of Asthma Phenotypes and Pharmacogenomic Interactions by Race-ethnicity; BMI, body mass index; FEV1, forced expiratory volume at 1 second; and WBC, white blood count.
*The coefficient of determination (R2) represented the percent of the variation in the outcome variable (i.e., mitochondrial copy number) that could be accounted for by each variable in the univariable analyses.
†Model 1 assessed the relationship between mitochondrial copy number in blood leukocytes (dependent variable) and asthma status (main explanatory variable). This model adjusted for patient age in years, sex (female = 1, male = 0), proportion of African ancestry, BMI, smoking status (past or never smoker = 0, active smoker = 1), and percent of predicted FEV1. Complete data were available for 3,675 individuals in Model 1, which had an adjusted R2 = 0.024.
‡Model 2 assessed the relationship between mitochondrial copy number in blood leukocytes (dependent variable) and asthma status (main explanatory variable). This model adjusted for absolute white blood cell counts and platelet counts (in increments of 1000 cells per microliter). Complete data were available for 2,031 individuals in Model 2, which had an adjusted R2 = 0.219.
§Model 3 assessed the relationship between mitochondrial copy number in blood leukocytes (dependent variable) and asthma status (main explanatory variable). This model adjusted for mitochondrial haplogroup, and only individuals with the L0, L1, L2, L3, and West Eurasian haplogroups were included. Complete data were available for 3,523 individuals in Model 3, which had an adjusted R2 = 0.020.
||Model 4 assessed the relationship between mitochondrial copy number in blood leukocytes (dependent variable) and asthma status (main explanatory variable); this model included all of the variables from models 1–3. Complete data were available for 1,942 individuals in Model 4, which had an adjusted R2 = 0.229.