The effect of smoking-related hyperhomocysteinemia on spirometric declines in chronic obstructive pulmonary disease in elderly Japanese

Smoking is implicated in chronic obstructive pulmonary disease (COPD) and hyperhomocysteinemia. To elucidate the role of hyperhomocysteinemia in COPD, we examined the relationship between plasma total homocysteine (tHcy) and spirometric declines in patients with COPD. We recruited 7 male never-smokers, 16 male control smokers, and 24 male patients with COPD. We investigated whether or not smoking might induce hyperhomocysteinemia in subjects predisposed to COPD, and then prospectively examined the relationship between plasma tHcy concentration and annual decline in FEV1.0 in the COPD group. We found that plasma tHcy concentrations declined among groups in the following order: COPD group > control group > never-smoker group. Furthermore, plasma tHcy concentrations in the COPD group were significantly correlated with %FEV1.0 (rs = 0.46). Also, COPD patients with severe airflow limitation showed a significant decrease in PaO2, which might be involved in the decreased tHcy in those patients. The prospective analysis revealed that plasma tHcy concentration, but not a history of smoking, were significantly correlated with the annual decline in FEV1.0 calculated by the difference in FEV1.0 between the first examination and an examination the following year (rs = 0.40). The present study suggests that smoking might increase plasma tHcy concentrations, leading to spirometric declines in subjects predisposed to COPD.