Changing area socioeconomic patterns in U.S. cancer mortality, 1950-1998: Part II--Lung and colorectal cancers.

BACKGROUND: Lung cancer and colorectal cancer are leading causes of U.S. cancer mortality. Because mortality rates for many cancers vary by socioeconomic characteristics, we used area socioeconomic indices to examine patterns in U.S. lung and colorectal cancer mortality between 1950 and 1998.
METHODS: A factor-based area socioeconomic index was linked to 1950-1998 county mortality data to generate annual lung and colorectal cancer mortality rates for each area socioeconomic group. Joinpoint regression analysis was used to model and identify statistically significant changes in the mortality trends.
RESULTS: Area socioeconomic patterns in U.S. lung cancer mortality changed dramatically between 1950 and 1998. Men aged 25-64 years and those aged 65 years or older in higher socioeconomic areas generally had higher lung cancer mortality than did those in lower socioeconomic areas during 1950-1964 and 1950-1980, respectively. Area socioeconomic differences in lung cancer mortality began to reverse and widen by the early 1970s for younger men and by the mid-1980s for older men. In 1998, lung cancer mortality was 56% (95% confidence interval [CI] = 49% to 64%) higher for younger men and 38% higher (95% CI = 34% to 43%) for older men in the lowest area socioeconomic group than for the same age groups in the highest area socioeconomic group. Lung cancer mortality among older women in all socioeconomic groups increased sevenfold to eightfold between 1950 and 1998, with higher mortality in higher area socioeconomic groups. The positive socioeconomic gradient in colorectal cancer mortality diminished substantially over time. Although colorectal cancer mortality among women in all area socioeconomic groups showed a consistent downward trend, colorectal cancer mortality among men in low area socioeconomic groups, but not in high area socioeconomic groups, showed an upward trend.
CONCLUSIONS: Socioeconomic gradients in male lung cancer mortality reversed between 1950 and 1998, and those in colorectal cancer mortality narrowed over that time. Area measures may be useful for monitoring socioeconomic disparities in cancer mortality and for identifying areas for potential cancer control interventions.