Summer is on its way and this means we are exposed to a lot more summer related allergies and with COPD even though there are multiple contributors to COPD such as tobacco smoke, occupational dusts, chemicals and air pollution, vitamin D and sun deficiencies may also play a role. 
Research has demonstrated that the severity of the disease is correlated directly to levels of vitamin D, and other research demonstrates that severe disturbed lung and peripheral muscle functions are more pronounced in COPD patients with vitamin D deficiency. In addition, recent research shows that cardiopulmonary exercise capacity is increased remarkably in people with high vitamin D levels compared to those with low levels. Of course, 90% of vitamin D blood levels are produced by sun exposure.
One may intelligently conclude, based on this information, that a part of the cause for both diseases is a lack of sun-derived vitamin D.
ref: http://sunlightinstitute.org/does-does-sun-exposure-have-an-influence-on-copd/
