Fig 2. Lung T₁ as a function of age and PY for all subjects.

The example line shows the correlation between median lung T₁ and age for smokers (●) and never smokers (○), indicating that lung T₁ shortens with ageing (p<0.01, r = -0.52). The smoking history of the current smokers is visualized with increased size of the dots ($\mathrm{•}$ = 1–10 PY, $\mathrm{•}$ = 11–20 PY, $\mathrm{•}$ = 21–30 PY and $\mathrm{•}$ = 31–40 PY).