VETSA1 MRI participants had significantly less average lifetime cigarette use (mean = 16.9 pack-years, SD = 21.6) compared to non-MRI participants (mean = 21.39 pack-years, SD = 2.23, p = 0.001). While MRI participants smoked fewer pack-years compared to non-participants, any bias is expected to attenuate rather than overstate the magnitude of effects reported in this study. Additionally, MRI participants were significantly older (mean = 55.8, SD = 2.6 years) than non-MRI participants (mean = 55.3, SD = 2.4 years, p = 0.0005), but this very small difference is due to the later start of the VETSA1 MRI study compared to the VETSA sample and is unlikely to affect the results.
