Table 3. Relationship between mitochondria haplogroup and copy number among African American participants in the SAPPHIRE and SAGE II cohorts stratified by asthma status*.
| Mitochondrial haplogroup† | SAPPHIRE cohort | SAGE II cohort | Meta-analysis | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Participants with asthma | Participants without asthma | P-value§ | Participants with asthma | Participants without asthma | P-value§ | Standardized difference (95% CI) | Heterogeneity P-value|| | P-value¶ | |||||
| No. | Mitochondria copy number (mean ± SD)‡ | No. | Mitochondria copy number (mean ± SD) ‡ | No. | Mitochondria copy number (mean ± SD) ‡ | No. | Mitochondria copy number (mean ± SD) ‡ | ||||||
| L0 | 122 | 204.66 ± 53.87 | 42 | 194.09 ± 72.85 | 0.392 | 42 | 232.17 ± 49.65 | 22 | 221.87 ± 74.60 | 0.564 | 0.18 (-0.11–0.47) | 0.988 | 0.233 |
| L1 | 516 | 220.56 ± 60.50 | 166 | 201.44 ± 60.22 | <0.001 | 149 | 232.97 ± 48.13 | 94 | 222.06 ± 58.82 | 0.133 | 0.28 (0.14–0.43) | 0.496 | <0.001 |
| L2 | 826 | 216.40 ± 56.96 | 262 | 196.14 ± 62.65 | <0.001 | 225 | 237.64 ± 59.24 | 145 | 214.73 ± 58.95 | <0.001 | 0.36 (0.24–0.48) | 0.754 | <0.001 |
| L3 | 1110 | 221.65 ± 60.33 | 298 | 205.67 ± 70.11 | <0.001 | 291 | 240.19 ± 66.28 | 174 | 232.89 ± 64.14 | 0.242 | 0.21 (0.10–0.32) | 0.214 | <0.001 |
| East Eurasian | 48 | 222.98 ± 44.89 | 13 | 220.80 ± 45.79 | 0.880 | 32 | 227.06 ± 57.03 | 17 | 212.99 ± 56.99 | 0.417 | 0.15 (-0.27–0.58) | 0.648 | 0.485 |
| West Eurasian | 141 | 208.98 ± 56.32 | 40 | 183.41 ± 58.31 | 0.016 | 61 | 227.25 ± 55.11 | 27 | 221.47 ± 47.55 | 0.619 | 0.32 (0.04–0.60) | 0.245 | 0.024 |
SAPPHIRE denotes the Study of Asthma Phenotypes and Pharmacogenomic Interactions by Race-ethnicity; SAGE II, Study of African Americans, Asthma, Genes, & Environment II; SD, standard deviation; and CI, confidence interval.
*The SAPPHIRE study sample was restricted to participants aged ≥18 years at enrollment and the SAGE II study samples was restricted to participants aged <20 years at enrollment.
†Geographical mitochondrial haplogroup assignments were based on those described by Pereira et al. (Am J Hum Genet. 2009; 84:628–40). Haplogroups L0, L1, L2, and L3 are considered to be African. Given the small number of study individuals with non-African haplogroups, we grouped most of the remaining haplogroups into the broad categories of East Eurasian and West Eurasian.
‡The mitochondrial copy number estimate was for whole blood. It was based on the sequencing read depth ratio between mitochondrial and nuclear DNA isolated from blood leukocytes.
§P-values were calculated using the Welch two sample t-test to compare mitochondrial copy numbers between individuals with and without asthma.
||Assessment of the difference in P-values from the SAPPHIRE and SAGE II cohorts. A P-value<0.05 would signify a statistically significant difference in the P-values between cohorts.
¶Meta-analysis P-value for the standardized difference in mitochondrial copy number between individuals within and without asthma for the SAPPHIRE and SAGE II cohorts combined.