Table 3

Baseline characteristics according to quartiles of CO levels

COLowest (Q1)
(n=9475)
Second (Q2)
(n=9867)
Third (Q3)
(n=11 429)
Highest (Q4)
(n=9005)
P value
AgeMean, SD62.938.6862.108.6961.968.8962.429.19
Men456748.2%450245.6%541647.4%421646.8%0.003
Insurance feeLowest190920.1%245524.9%342229.9%272430.2%<0.001
Second127613.5%172417.5%221119.3%188320.9%
Third451147.6%334533.9%289925.4%223024.8%
Highest177918.8%234323.7%289725.3%216824.1%
UrbanizationHighly105911.2%238024.1%372332.6%480653.4%<0.001
Moderately278629.4%397640.3%382333.4%235426.1%
Boomtown127713.5%141714.4%229720.1%116813.0%
Others435345.9%209421.2%158613.9%6777.5%
AMD*2973.1%2442.5%3733.3%5215.8%<0.001
Alcoholism5195.5%5275.3%5805.1%4234.7%0.081
IHD406842.9%405741.1%446939.1%364440.5%<0.001
COPD306332.3%303330.7%326628.6%255628.4%<0.001
DM233524.6%226022.9%276324.2%222624.7%0.011
Hyperlipidemia401742.4%423843.0%504044.1%409345.5%<0.001
Hypertension672070.9%684069.3%784768.7%623269.2%0.004
  • *Indicating newly diagnosed AMD during follow-up rather than baseline patients with AMD.

  • AMD, age-related macular degeneration; CO, carbon monoxide; COPD, chronic obstructive pulmonary disease; DM, diabetes mellitus; IHD, ischemic heart disease.