Table 2– Comparison of lung function decline and vitamin D status between rapid decliners and slow decliners, matched on date of phlebotomy (to within 60 days) and clinical centre

Characteristic	Rapid decliners	Slow decliners	p-value
Participants	98	98
Rate of FEV₁ decline from Y5 to LT mL·yr⁻¹	-151.6±47.7	-0.28±24.0	<0.0001
Rate of FEV₁ decline from Y5 to LT % pred·yr⁻¹	-4.3±1.2	+0.7±0.7	<0.0001
Y5 25(OH)D levels ng·mL⁻¹	25.0±10.4	25.9±10.2	0.54

Data are presented as n or mean±sd, unless otherwise stated. p-values calculated using paired t-testing. FEV₁: forced expiratory volume in 1 s; Y5: year 5 visit; LT: long-term follow-up visit; % pred: % predicted; 25(OH)D: 25-hydroxyvitamin D.