RT Journal Article SR Electronic T1 Is low level of vitamin D a marker of poor health, or a cause? JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 1800931 DO 10.1183/13993003.00931-2018 VO 51 IS 6 A1 Om P. Kurmi YR 2018 UL http://erj.ersjournals.com/content/51/6/1800931.abstract AB