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Table 4 Adjusted associations of BMI and activity (occupational/ leisure) at 36, 43, and 53 years with kOA in women

From: Body mass index, occupational activity, and leisure-time physical activity: an exploration of risk factors and modifiers for knee osteoarthritis in the 1946 British birth cohort

  36 years 43 years 53 years
  OR p-value OR p-value OR p-value
Manual occupation 1.85 (1.06, 3.24) 0.031 1.09 (0.66, 1.82) 0.734 1.87 (1.22, 2.86) 0.004
Non-manual occupation Referent   Referent   Referent  
BMI (per z-score) 1.49 (1.16, 1.91) 0.002 1.73 (1.39, 2.15) <0.001 1.92 (1.59, 2.33) <0.001
 p-value for test of interaction   0.691   0.570   0.203
Lifting unlikely 0.89 (0.51, 1.55) 0.681 1.10 (0.67, 1.81) 0.710 0.71 (0.42, 1.19) 0.317
Lifting somewhat likely Referent   Referent   Referent  
Lifting highly likely 0.73 (0.32, 1.66) 0.449 1.09 (0.55, 2.18) 0.070 1.02 (0.51, 2.07) 0.590
BMI (per z-score) 1.80 (1.47, 2.21) <0.001 1.85 (1.52, 2.25) <0.001 1.73 (1.49, 2.24) <0.001
 p-value for test of interaction   0.344   0.580   0.808
Kneeling unlikely 0.74 (0.49, 1.11) 0.143 0.79 (0.52, 1.18) 0.248 0.93 (0.58, 1.51) 0.776
Kneeling somewhat likely Referent   Referent   Referent  
Kneeling highly likely 0.91 (0.45, 1.85) 0.793 0.80 (0.41, 1.59) 0.530 1.23 (0.58, 2.61) 0.582
BMI (per z-score) 1.78 (1.45, 2.18) <0.001 1.83 (1.50, 2.22) <0.001 1.91 (1.29, 2.83) <0.001
 p-value for test of interaction   0.295   0.780   0.405
Sitting unlikely 1.15 (0.72, 1.84) 0.549 0.76 (0.47, 1.24) 0.276 1.29 (0.77, 2.16) 0.343
Sitting somewhat likely Referent   Referent   Referent  
Sitting highly likely 0.56 (0.33, 0.94) 0.029 0.57 (0.36, 0.89) 0.013 0.89 (0.56, 1.43) 0.653
BMI (per z-score) 1.77 (1.45, 2.18) <0.001 1.80 (1.48, 2.19) <0.001 1.48 (1.41, 2.22) <0.001
 p-value for test of interaction   0.292   0.846   0.234
Inactive 1.00 (0.63, 1.60) 0.985 0.73 (0.47, 1.13) 0.153 1.46 (0.87, 2.47) 0.154
Less active Referent   Referent   Referent  
Most active 0.99 (0.61, 1.63) 0.978 0.50 (0.28, 0.91) 0.022 0.67 (0.37, 1.21) 0.184
BMI (per z-score) 1.85 (1.51, 2.25) <0.001 1.82 (1.50, 2.20) <0.001 1.84 (1.52, 2.23) <0.001
 p-value for test of interaction   0.118   0.005   0.414
  1. OR Odds Ratio, BMI Body Mass Index.
  2. Note: separate models were examined for each activity exposure and BMI and coefficients reported are from models without a BMIxActivity interaction, adjusting for potential confounders - education at 26y, income at 53y, childhood social class, family history of arthritis, history of knee injury and health status at 53y. Where there was evidence for an interaction, Figures 1C and 1D show the full stratified odds ratios for BMI and activity in these models.