Oxidative stress in smokers with and without COPD: what variables are associated?

Oxidative stress induced by cigarette smoke compounds is one of the factors responsible for bronchial inflammation and airway structural remodeling. On the other side, the individual antioxidant capacity is variable and representative of the body's immune defenses' state. The aim of this study is to detect the level of oxidative stress and anti-oxidant capacity in smokers, comparing COPD with non-COPD patients. To determine the variables associated with oxidative stress.

Fifty-four patients were assessed by spirometry and questionnaires such as CAT, mMRC, Fagestrom's. The exhaled carbon monoxide (eCO) was measured in order to assess smoking exposure. Serum vitamin-D level was also detected. All patients underwent treatment for smoking cessation by Cytisine, an alkaloid partial agonist of the nicotinic acetylcholine receptor. The diagnosis of COPD was determined based on FEV1/FVC ratio <70%. Oxidative stress and anti-oxidant capacity were determined on a saliva sample using commercial assays, after the last cigarette smoked. Data were analyzed using non-parametric statistical tests.

In the overall population, the average value of the pack-years index was 40, the Fagestrom's mean value was 5, BMI was 26, exhaled CO (eCO) was 27 ppm. Comparing the two subgroups, COPD and no-CODP, they were comparable in age, Fagestrom's, pack-years. They obviously differed in the functional variables. The d-ROMs value was significantly higher in smokers who had not developed COPD (P<0.01). This group had a lower level of vitamin D than the COPD group (P<0.03), a different value of cigarettes/day (P<0.0001) as well as the value of eCO were detected (P<0.01). In multiregression analysis d-ROMs value is correlated with pack-years and cigarette/day values. d-ROMs, cigarettes/day, vitamin D value were factors affecting COPD.

Our results confirm that tobacco smoking causes oxidative stress, and it is associated with pack-years index and cigarettes/day. COPD patients with a high vitamin D level are protected from oxidative stress.