Practical Applications
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Methodological differences likely account for the
This study was reviewed and was determined to be exempt from institutional board review by Dartmouth College's Committee for the Protection of Human Subjects.
We were able to very nearly reproduce the findings of Jones et al7 that are reported in Table 1, using weighted data and adjusting for the complex sampling frame of the NHIS. Based on our replication of the Jones et al7 methods and analyses, we found that chiropractic users were significantly less likely than nonusers to have received the pneumococcal vaccine, and we found no significant difference between the 2 groups in having received both flu and pneumococcal vaccines (OR, 0.91; 95% CI,
From our analyses, it is apparent that methodological differences likely account for the previous divergent findings from 2 prior analyses6, 7 that used NHIS data to look at the potential relationship between chiropractic care use and preventive vaccination (Table 1). The 2 studies6, 7 used different CDC criteria and different years of NHIS source data and differed in their selection of comparison groups, in their operationalization of covariate variables, and in their design of regression
We used the 2007 NHIS to further explore the relationship between having used chiropractic care and adult immunization, more specifically, adult influenza immunization. Our study finds that methodological differences vary widely in the literature among previous studies that have explored this relationship. These differences likely explain the divergent findings reported. In addition, the CDC's criteria used to identify adults that are “high priority” for immunization has changed considerably
Smith was supported by Award Number 1K01AT002391 from the National Center for Complementary and Alternative Medicine. Davis was supported by Award Number 1K01AT006162 from the National Center for Complementary and Alternative Medicine.
The views expressed herein do not necessarily represent the views of the National Center for Complementary and Alternative Medicine or the National Institutes of Health.
The authors reported no conflicts of interest. Methodological differences likely account for the Practical Applications
Other analyses mainly focused on vaccination uptake in chiropractic patients. Potentially based on different assessment time points and methodology, those analyses found that patients who had consulted chiropractors were less likely [8], equally likely [9] or even more likely [7] to use influenza vaccination than patients not consulting chiropractors. A comparable pattern with inconsistent results occurred for patients who had consulted non-chiropractic providers of CM.
For example, analyses from NHIS data in the US has drawn contrasting results of the correlation between chiropractic use and the uptake of the influenza vaccine, showing chiropractic use as being correlated with both higher influenza vaccine use (Stokley et al., 2008) and lower vaccine use (Jones et al., 2010) in different studies. Re-analysis of this data by different authors has suggested these differences are dependent on the definition of chiropractic use is employed (i.e. ‘ever used’ versus ‘have used in past 12 months’) and how ‘high-priority’ conditions for vaccination were built into the multiple regression model (Smith and Davis, 2011). Additional re-analysis of this dataset also determined that for high-priority patients there were no significant differences in vaccination uptake between those patients who used chiropractic and those who did not use chiropractic (Davis et al., 2012).
Research was conducted as Associate Professor, Palmer Center for Chiropractic Research, Palmer College of Chiropractic, San Jose, CA.