Grauman D J, Tarone R E, Devesa S S, Fraumeni J F
Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD 20892, USA.
J Natl Cancer Inst. 2000 Apr 5;92(7):534-43. doi: 10.1093/jnci/92.7.534.
Mapping techniques can highlight the spatial or temporal variations in rates of cancer mortality. In mapping geographic patterns of cancer mortality, spatial units are grouped into categories defined by specified rate ranges, and then the units in each category are assigned a particular color in the map. We examined the consequences of using different ranging methods when comparing maps over several time intervals.
Maps of mortality rates for cancers of the breast, lung (including the lung, trachea, bronchus, and pleura), and cervix uteri in the United States by county or state economic area are created for different time intervals between 1950 and 1994. Two ranging methods are employed: 1) Ranges are defined for individual time interval by the deciles of rates in that interval (ranging within intervals), and 2) constant ranges for all time intervals are defined by the deciles of rates for the entire 45-year period from 1950 through 1994 (ranging across intervals). The time intervals from 1950 through 1969 and from 1970 through 1994 were chosen to accommodate the availability of detailed county-level population estimates specifically for blacks starting in 1970.
The ranging method has little impact on maps for breast cancer mortality, which changed little over time. For lung cancer, which increased over time, and cervix uteri cancer, which decreased over time, ranging within time intervals shows the geographic variability but does not convey the temporal trends. Trends are evident when ranging across time intervals is employed; however, geographic variability is partially obscured by the predominance of spatial units in the highest rate categories in the recent time intervals for lung cancer and in the early time intervals for cervix uteri cancer.
Ranging within time intervals displays geographic patterns and changes in geographic patterns, regardless of time trends in rates. Ranging across time intervals shows temporal changes in rates but with some loss of information about geographic variability.
制图技术能够突出癌症死亡率的空间或时间变化。在绘制癌症死亡率的地理模式图时，空间单元会被归为按特定死亡率范围定义的类别，然后在地图上为每个类别中的单元赋予一种特定颜色。我们研究了在比较多个时间间隔的地图时使用不同分级方法的后果。
针对1950年至1994年期间的不同时间间隔，绘制了美国按县或州经济区域划分的乳腺癌、肺癌（包括肺、气管、支气管和胸膜）及子宫颈癌死亡率地图。采用了两种分级方法：1）按各个时间间隔内死亡率的十分位数为单个时间间隔定义范围（区间内分级），2）按1950年至1994年整个45年期间死亡率的十分位数为所有时间间隔定义固定范围（跨区间分级）。选择1950年至1969年以及1970年至1994年这两个时间间隔，以适应自1970年起开始提供的详细县级黑人人口估计数据。
分级方法对乳腺癌死亡率地图影响不大，其随时间变化较小。对于随时间增加的肺癌和随时间减少的子宫颈癌，区间内分级显示了地理变异性，但未传达时间趋势。采用跨区间分级时趋势明显；然而，对于肺癌，近期时间间隔内最高死亡率类别的空间单元占主导，对于子宫颈癌，早期时间间隔内最高死亡率类别的空间单元占主导，这部分掩盖了地理变异性。
区间内分级展示了地理模式及地理模式的变化，无论死亡率的时间趋势如何。跨区间分级显示了死亡率的时间变化，但在一定程度上丢失了有关地理变异性的信息。
