Table 2

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

VariablesCumulative knee OA incidence at 8 years
n (%)*
Adjusted HR95% CI†
Gender (male)0.5900.491 to 0.712
Age1.0070.997 to 1.017
BMI1.0661.047 to 1.085
WOMAC (total)1.0181.010 to 1.026
Contralateral OA at baseline1.5931.328 to 1.900
mtDNA haplogroups (N=2579)
 H (n=1042)278 (26.7%)1
 UK (n=612)154 (25.1%)0.9080.727 to 1.131
 T (n=275)67 (24.3%)0.8960.658 to 1.221
 J (n=236)47 (20.1%)0.6800.470 to 0.968
 Others§ (n=414)102 (24.6%)0.8950.698 to 1.153
Gender (male)0.8690.698 to 1.043
Age1.0070.990 to 1.026
BMI1.0050.987 to 1.025
WOMAC (total)1.0061.001 to 1.012
Contralateral OA at baseline1.3131.087 to 1.576
mtDNA haplogroups (N=635)
 H (n=269)248 (92.2%)1
 UK (n=144)126 (87.5%)0.8490.682 to 1.035
 T (n=68)64 (94.1%)1.1330.850 to 1.447
 J (n=56)46 (82.1%)0.7280.469 to 0.998
 Others§ (n=98)86 (87.7%)0.8100.627 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.