Urbanicity-related trends in lung cancer mortality in US counties: White females and white males, 1970-1987

Background. The effect of urbanization on age-adjusted lung cancer mortality rates in US counties is investigated, The data come from National Cancer Institute, and urban trends are estimated in time periods 1970-1979 and 1980-1987, for both white males and white females. To account for possibly different gradients in different parts of the country, the 48 contiguous states are divided into seven regions. Methods. A measure of urbanness, urbanicity, is defined and is used to stratify counties. A multiplicative model is proposed that relates county mortality rates to urbanicity. The residuals from this multiplicative model serve as age- and urban-adjusted rates. Results. Urban-rural gradients are significant for nearly all regions for both white males and white females, diminishing slightly in the latter time period for white males but becoming stronger for white females. Conclusions. The age- and urban-adjusted rates may be used in mapping to investigate geographical patterns that remain after removal of the urban factor.