Table III.

Risk of severe exacerbation over four years by combination of inhaled corticosteroid use and vitamin D status

	No	Yes	%	Odds ratio1
On inhaled steroids, sufficient vitamin D	162	52	24%	1.0 (reference)
On inhaled steroids, insufficient vitamin D	58	31	35%	1.7 (1.0–2.9)
Not on steroids, sufficient vitamin D	289	158	35%	1.7 (1.2 – 2.5)
Not on steroids, insufficient vitamin D	166	105	39%	2.0 (1.3 – 2.9)

¹Odds ratios are for each stratum in reference to a subject on inhaled corticosteroids with sufficient vitamin D. The Cochran-Armitage two-sided P-value for trend over the four strata is .0009.