Table 5

Relationship between serum 25(OH)D concentrations and FEV₁ (n=1197), FVC, FEV₁/FVC and COPD (n=1195)

	FEV₁			FEV₁/FVC
	Regression coefficient (l)^*	95% CI	p Value	Regression coefficient^*	95% CI	p Value
Fifths of 25(OH)D:
1 (lowest)	–	–	–	–	–	–
2	0.027	(−0.057 to 0.111)	0.526	0.008	(−0.007 to 0.022)	0.310
3	−0.053	(−0.138 to 0.031)	0.215	−0.003	(−0.017 to 0.012)	0.729
4	−0.004	(−0.091 to 0.083)	0.936	−0.008	(−0.024 to 0.007)	0.278
5 (highest)	0.008	(−0.081 to 0.098)	0.852	−0.008	(−0.024 to 0.007)	0.296

Effect per quintile increase in 25(OH)D	−0.002	(−0.022 to 0.019)	0.885	−0.003	(−0.007 to 0.000)	0.07

	FVC			COPD
	Regression coefficient (l)^*	95% CI	p Value	OR^*	95% CI	p Value
Fifths of 25(OH)D:
1 (lowest)	–	–	–	–	–	–
2	0.010	(−0.084 to 0.104)	0.831	0.992	(0.544 to 1.811)	0.980
3	−0.058	(−0.152 to 0.037)	0.229	1.230	(0.678 to 2.230)	0.496
4	0.023	(−0.074 to 0.121)	0.640	1.728	(0.959 to 3.114)	0.069
5 (highest)	0.049	(−0.051 to 0.149)	0.336	1.524	(0.824 to 2.819)	0.179

Effect per quintile increase in 25(OH)D	0.011	(−0.012 to 0.034)	0.342	1.151	(1.002 to 1.321)	0.046

↵* Adjusted for smoke in home, smoker status, pack years, age left education, home ownership status, no. of rooms, no. of cars, social class, fat mass, activity score, alcohol, dietary supplement use, birth weight, father's social class at birth, inhaled or oral steroids use and paracetamol use, and season of clinic visit. Age, height and gender were also included in the COPD analyses.
COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; 25(OH)D, 25 hydroxy vitamin D.