Blood Collection: During every visit, study personnel will take two 10 ml collection of blood from participants through venipuncture (using standard techniques). Samples will be centrifuged and the serum component will be aliquoted into special tubes (provided by the coordinating site) that contain anti-proteases. They will then be shipped (Fedexed) in regular ice immediately to the Study Coordinating Center (to arrive within 24 hours of blood collection) where they will be frozen in liquid nitrogen and stored in -70ºC freezers until analysis. To avoid delays, no samples will be taken on a Friday or a day preceding holidays. A high-sensitive solid phase enzyme-linked immunosorbent assay (ELISA) to measure serum CRP will be used. The investigators have measured over 4,000 serum samples from the Lung Health Study with this technique. In comparison with nephelometry, another commonly used technique, CRP levels with high-sensitivity ELISA is excellent. The coefficient of variation for CRP in the researchers' laboratory is ~5%. IL-6 and MCP-1 will also be measured using high-sensitivity ELISA assays. The researchers' laboratory has also experience performing these assays using serums collected from COPD patients. The investigators have previously shown that the coefficient of variation for the IL-6 assay to be 4.7% (median; interquartile range, 1.8% to 11.2%) and the MCP-1 assay to be 3.2% (median; interquartile range, 1.5% to 5.9%).