chiropractic, life expectancy
J Hart. Does Chiropractic “Add Years to Life”? A Second Look. The Internet Journal of Chiropractic. 2012 Volume 1 Number 2.
Introduction: A 2004 study found no evidence to support the claim made in the cliché, “chiropractic adds years to life.” Among the flaws in that study was a comparison of a 26 year period to only a two year period for life expectancies. The present study provides a re-analysis of that data.Methods: Average chiropractor age at death for each of the 26 years from the 2004 study were compared to life expectancy for matching years for a total of 26 comparisons.
Results: Average age for chiropractors was: a) 1.2 years higher than average life expectancy (though not statistically significant, with a small effect size) and b) higher in 17 out of the 26 (65.4%) years compared.Discussion: Flaws in the 2004 study prevent a meaningful conclusion to drawn in the present study. Although the calculations in this study favor the claim made in the cliché, their lack of statistical significance and small effect size prevent also prevent a firm conclusion. Conclusion: The question of whether chiropractic adds years to life would best be answered by a properly designed study.
A study from 2004 1challenged the chiropractic cliché, “chiropractic adds years to life,” and found no evidence to support the claim stated in the cliché. That study obtained age at death for a convenience sample of male chiropractors, presumably Caucasian, from two sources: 1)
This author notes other limitations of the 2004 study. First, it omitted chiropractor deaths due to un-natural causes such as accidents. While this omission may actually inflate the chiropractor ages, it nonetheless prevents a valid comparison to longevity tables that include deaths from all causes. Interestingly, a casual search in
The present study uses the same chiropractor data from the 2004 study with a modification of averaging multiple chiropractor ages at death for a single year. If a particular year had only one chiropractor death, that age was used for that year. This method was used for each of the 26 years included in the 2004 study (1969-1979 and 1989-2003) for a total of 26 comparisons. The author was unable to locate age at death for medical doctors for years matching the chiropractor years used in the 2004 study.
Average life expectancy data (LE) for U.S. white males was obtained from U.S. Census Databases for years 1969-1979, and 1989-2003, 6-7which, as noted previously, were the chiropractor years used in the 2004 study. LE and chiropractor age at death (CA) were compared for differences by subtracting LE from CA, and then noting the number of years that CA was greater than the LE. In addition, differences between these two variables (LE and CA) were analyzed to determine if their difference was statistically significant.
Data analysis was performed in Stata IC 12.1 (StataCorp, College Station, TX). Histogram inspection of the differences between two variables revealed a fairly normal distribution. Consequently, the two variables (LE and CA) were compared using the paired
In more than half of the years, 17 out of the 26 (65.4%), chiropractor age at time of death (CA) was greater than life expectancy for white males in the U.S. (LE) for matching years (Table 1). In addition, average CA was 1.2 years higher than the average LE. Specifically, average CA was 73.1 years of age (SD 7.6) compared to average LE which was 71.9 years of age (SD 2.6), a difference though that was not statistically significant (p = 0.4499). A small effect size (of 0.21) was observed between CA and LE.
No firm conclusions can be made from the present study due to the lack of statistical significance in comparing CA and LE. However, there is weak evidence that CA is greater than LE because: a) the percent of years where CA was greater than LE (65.4%), and b) the effect size, though small (0.21), indicating a small practical difference between CA and LE.
Given the problems with the 2004 study (e.g., non-random sampling of chiropractors, non- sampling of chiropractic patients, and non-matching years for many of the years compared), the findings of that study, and therefore the present study cannot easily be generalized to either the general population of chiropractors or to their patients. Future study should include people (chiropractors and /or non-chiropractors) who are known to be actual patients, to determine the effect, if any, of chiropractic care on life expectancy.
Firm conclusions are not possible in either the present study or the 2004 study for the reasons outlined in this re-analysis. Future research intended to answer the question of whether chiropractic “adds years to life” should, at a minimum, include: a) a sample of chiropractic