Association of Heart Disease Mortality Rates with Concentrations of Chiropractors and Medical Doctors in the U.S., 2007

摘要

Introduction: It is presumed that as concentration of health care practitioners increases, health outcomes such as heart disease mortality rates (HDMR) decrease. This ecological study compares HDMRs with concentrations of: a) doctors of chiropractic (“DC ratios”) and medical doctors (“MD ratios”).Methods: The ratios were calculated by dividing total population in each state by total numbers of DCs and MDs in each state. The ratios were then compared to heart disease mortality rates using Pearson correlation and multiple linear regression.Results: DC ratios showed stronger associations with decreased HDMR compared to MD ratios. Discussion: Reasons for the stronger DC ratio associations are unclear. Two possible explanations are: a) dietary services that many DCs provide may not be provided generally by MDs, and b) spinal manipulation (also known as “adjustment”) may have, by way of neurological pathways, visceral benefits. Limitations to the study are its ecological design, where populations rather than individuals are studied. The study is intended only as a first step for further research.Conclusion: DC ratios showed stronger associations with decreased HDMR compared to MD ratios in this study. Further research with other designs, such as the case-control design is indicated. Since this is an observational study, causal inference is not claimed. Introduction Obviously many factors affect health, such as socioeconomic factors and genetics. It would seem that the supply of health care practitioners would also affect health. There is some evidence showing that primary care medical doctor supply is related to improved health outcomes 1-2 but the relationship is not as strong compared to socioeconomic factors. 1Other evidence suggests that there is no association between physician supply and mortality rates. 3Such findings appear to be based on ecological designs, where populations rather known individuals are studied. There are few, if any studies comparing: a) DCs and mortality rates to b) MDs and mortality rates. A previous study correlated DC and MD supplies with various health outcomes. 4In that study, the year for the doctor data (2004) was different than the years the outcomes were based on (from 1999-2003). The present study compares DC and MD ratio data for 2005 and heart disease mortality rates (HDMR) for 2007. This outcome was selected because a) it was the top single cause of death for that year 5 and b) there is plausibility in subtle problems of the spine and heart problems. 6-10The purpose of the study is not to determine what the causes or cures are for heart disease, as the main factors for heart disease are already known. The purpose of the study is instead simply to compare the strength of association of DC ratios and HDMR with MD ratios and HDMR. An assumption of the study is that increased concentration of a profession (DC or MD) is directly related to increased services from the profession while an expectation is that their increased concentration results in decreased HDMR.. Methods Age-adjusted HDMR death rates per 100,000 population from 2007 for all 50 states and the District of Columbia (“states”) were obtained. 5 DC 11 and MD 12 data were obtained for 2005 by dividing their respective total state population numbers by state in 2005 (in thousands) 13 by their total practitioner numbers by state. These values are referred to as “DC ratios” and “MD ratios.” As an example regarding how a ratio was calculated, Alabama’s population in thousands was 4,558 (4,558,000) and its DC number was 776. Thus, the DC ratio for Alabama is 4,558,000 / 776 or 5873.7/1 (or simply 5873.7). This means there was one DC to every 5874 persons in the state. The MD number for Alabama was 10,809, making its MD ratio 421.7. Consequently, smaller ratio numbers (e.g., 421.7 versus 5873.7) reflect greater concentration of practitioners. Data analysis consisted of Pearson correlation and linear regression in Stata IC 12.1 (StataCorp, Coll