Cumulative probability of incident knee OA at 8 years in subjects from the OAI and CHECK cohorts according to mtDNA haplogroups and results of the extended Cox proportional hazard model
| Variables | Cumulative knee OA incidence at 8 years n (%)* | Adjusted HR | 95% CI† |
|---|---|---|---|
| OAI | |||
| Gender (male) | 0.590 | 0.491 to 0.712‡ | |
| Age | 1.007 | 0.997 to 1.017 | |
| BMI | 1.066 | 1.047 to 1.085‡ | |
| WOMAC (total) | 1.018 | 1.010 to 1.026‡ | |
| Contralateral OA at baseline | 1.593 | 1.328 to 1.900‡ | |
| mtDNA haplogroups (N=2579) | |||
| H (n=1042) | 278 (26.7%) | 1 | |
| UK (n=612) | 154 (25.1%) | 0.908 | 0.727 to 1.131 |
| T (n=275) | 67 (24.3%) | 0.896 | 0.658 to 1.221 |
| J (n=236) | 47 (20.1%) | 0.680 | 0.470 to 0.968‡ |
| Others§ (n=414) | 102 (24.6%) | 0.895 | 0.698 to 1.153 |
| CHECK | |||
| Gender (male) | 0.869 | 0.698 to 1.043 | |
| Age | 1.007 | 0.990 to 1.026 | |
| BMI | 1.005 | 0.987 to 1.025 | |
| WOMAC (total) | 1.006 | 1.001 to 1.012‡ | |
| Contralateral OA at baseline | 1.313 | 1.087 to 1.576‡ | |
| mtDNA haplogroups (N=635) | |||
| H (n=269) | 248 (92.2%) | 1 | |
| UK (n=144) | 126 (87.5%) | 0.849 | 0.682 to 1.035 |
| T (n=68) | 64 (94.1%) | 1.133 | 0.850 to 1.447 |
| J (n=56) | 46 (82.1%) | 0.728 | 0.469 to 0.998‡ |
| Others§ (n=98) | 86 (87.7%) | 0.810 | 0.627 to 1.032 |
*Cumulative incident knee OA rate from baseline to follow-up.
†CIs for the HRs obtained using the bootstrap methodology by the improved percentile method.
‡Statistical significance declared at p≤0.05.
§The group ‘others’ include mtDNA variants with a frequency below 5%.
Bold refers to parameters that reached the statistical significance (p≤0.05).
BMI, body mass index; CHECK, cohort hip and cohort knee; mtDNA, mitochondrial DNA; OA, osteoarthritis; OAI, osteoarthritis initiative, WOMAC, Western Ontario and McMaster Universities Arthritis Index.