Shi Leiyu, Macinko James, Starfield Barbara, Wulu John, Regan Jerri, Politzer Robert
Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
J Am Board Fam Pract. 2003 Sep-Oct;16(5):412-22. doi: 10.3122/jabfm.16.5.412.
This study tests the robustness of the relationships between primary care, income inequality, and population health by (1) assessing the relationship during 4 time periods-1980, 1985, 1990 and 1995; (2) examining the independent effect of components of the primary care physician supply; (3) using 2 different measures of income inequality (Robin Hood index and Gini coefficient); and (4) testing the robustness of the association by using 5-year time-lagged independent variables.
DATA SOURCES/STUDY SETTING: Data are derived from the Compressed Mortality Files, the US Department of Commerce and the Census Bureau, the National Center for Health Statistics, the Centers for Disease Control and Prevention, and the American Medical Association Physician Master File. The unit of analysis was the 50 US states over a 15-year period.
Ecological, cross-sectional design for 4 selected years (1980, 1985, 1990, 1995), and incorporating 5-year time-lagged independent variables. The main outcome measure is age-standardized, all-cause mortality per 100,000 population in all 50 US states in all 4 time periods.
DATA COLLECTION/EXTRACTION METHODS: The study used secondary data from publicly available data sets. The CDC WONDER/PC software was used to obtain mortality data and directly standardize them for age to the 1980 US population. Data used to calculate the income inequality measure came from the US census population and housing summary tapes for the years 1980 to 1995. Counts of the number of households that fell into each income interval along with the total aggregate income and the median household income were obtained for each state. The Gini coefficient for each state was calculated using software developed for this purpose.
In weighted multivariate regressions, both contemporaneous and time-lagged income inequality measures (Gini coefficient, Robin Hood Index) were significantly associated with all-cause mortality (P <.05 for both measures for all time periods). Contemporaneous and time-lagged primary care physician-to-population ratios were significantly associated with lower all-cause mortality (P <.05 for all 4 time periods), whereas specialty care measures were associated with higher mortality (P <.05 for all time periods, except 1990, where P <.1). Among primary care subspecialties, only family medicine was consistently associated with lower mortality (P <.01 for all time periods).
Enhancing primary care, particularly family medicine, even in states with high levels of income inequality, could lead to lower all-cause mortality in those states.
本研究通过以下方式检验初级保健、收入不平等与人群健康之间关系的稳健性：（1）评估1980年、1985年、1990年和1995年这4个时间段内的关系；（2）考察初级保健医生供应各组成部分的独立作用；（3）使用两种不同的收入不平等衡量指标（罗宾汉指数和基尼系数）；（4）通过使用滞后5年的自变量来检验关联的稳健性。
数据来源/研究背景：数据源自压缩死亡率文件、美国商务部、人口普查局、国家卫生统计中心、疾病控制与预防中心以及美国医学协会医生主文件。分析单位是15年间的美国50个州。
针对4个选定年份（1980年、1985年、1990年、1995年）采用生态横断面设计，并纳入滞后5年的自变量。主要结局指标是4个时间段内美国所有50个州每10万人口的年龄标准化全因死亡率。
数据收集/提取方法：本研究使用来自公开可用数据集的二手数据。利用疾病预防控制中心的WONDER/PC软件获取死亡率数据，并将其直接按年龄标准化为1980年的美国人口数据。用于计算收入不平等衡量指标的数据来自1980年至1995年的美国人口普查人口与住房汇总磁带。获取每个州落入每个收入区间的家庭数量、总收入汇总以及家庭收入中位数。使用为此目的开发的软件计算每个州的基尼系数。
在加权多变量回归中，同期和滞后的收入不平等衡量指标（基尼系数、罗宾汉指数）均与全因死亡率显著相关（所有时间段两种指标的P值均<.05）。同期和滞后的初级保健医生与人口比例与较低的全因死亡率显著相关（所有4个时间段的P值均<.05），而专科护理指标与较高的死亡率相关（除1990年P值<.1外，所有时间段的P值均<.05）。在初级保健亚专业中，只有家庭医学始终与较低的死亡率相关（所有时间段的P值均<.01）。
即使在收入不平等程度较高的州，加强初级保健，特别是家庭医学，也可能导致这些州的全因死亡率降低。
