Although odds ratios often are calculated from prospective study data, in general, they should not be considered to provide estimates of risk. Estimates of odds ratios or risk ratios that have confidence intervals that include only values greater than 1.0 are considered to be statistically significant and to support a positive association or increased risk, respectively. Studies that include larger numbers of cases have narrower confidence intervals, that is, provide a more precise estimate of association or risk. If the estimated prevalence or incidence rate in the reference group is much lower than for the general population, odds ratios or risk ratios may be inflated and should be interpreted cautiously. Finally, it is important to consider the findings from a single study in the context of the totality of evidence, either qualitatively or quantitatively in a formal meta-analysis.
Smoking is known to depress antioxidants and to alter choroidal blood flow.
Risk ratios of 2.0 or greater were found for 40 to 45 pack-years or more. Hypertension is believed to damage the choroidal vasculature. Fewer data are available for evaluating possible associations of AMD with serum lipid levels and with atherosclerotic carotid artery disease. Findings to date are inconsistent. Odds ratios and risk ratios estimated in most studies have been 2.0 or greater.