Kosloff et al. Chiropractic & Manual Therapies (2015) 23:19
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overall sample, or for samples stratified by age. No estimated odds ratio was significant at the 95% confi- dence level. MA data were insufficient to calculate statistical measures of association for hazard periods less than 0 – 14 days for chiropractic visits. When stratified by age, the data were too sparse to calculate measures of association for hazard periods less than 0 – 30 days in the commercial population. The data were too few to analyze associative risk by headache and/or neck pain diagnoses (data not shown). These results showed there is an association existing between PCP visits and VBA stroke incidence regardless of age or length of hazard period. A strong association was found for those visits close to the index date (OR 11.56; 95% CI 6.32-21.21) for all patients with a PCP visit within 0 – 1 day hazard period in the commercial sample. There was an increased risk of VBA stroke asso- ciated with each PCP visit within 30-days prior to the index date for MA patients (OR 1.51; 95% CI 1.32-1.73) and commercial patients (OR 2.01; 95% CI 1.77-2.29). The findings of the secondary analysis showed – that of 1159 stroke cases from commercial population – there were a total of 19 stroke cases associated with chiropractic visits for which 13 (68%) had claims docu- mentation indicating chiropractic SMT was performed. For the control group of the commercial cohort, 62 of 4633 controls had claims of any kind of chiropractic visits and 47 of 4633 controls had claims of SMT. In the commercial control group, 47 of 62 DC visits (76%) in- cluded SMT in the claims data. Only 1 of 2 stroke cases in the MA population included SMT in the claims data. For the MA cohort, 21 of 24 control chiropractic visits (88%) included SMT in the claims data (Table 9). None of the stroke cases in either population included CPT 97140 as a substitute for the more conventionally re- ported chiropractic manipulative treatment procedural codes (98940 – 98942). For the control groups, there were three instances where CPT 97140 was reported without CPT 98940 – 98942 in the commercial population. The CPT code 97140 was not reported in MA control cohort.
Table 2 Age and gender of cases and controls (Medicare) Variable Cases (n = 670) Controls (n = 2680) Age: mean (median) 76.1 (76.2) 76.1 (76.2) Males: n (%) 393 (58.6) 1572 (58.6)
heart disease (ICD-9 410 – 414), disease of pulmonary cir- culation (ICD-9 415 – 417), other forms of heart disease (ICD-9 420 – 429), pure hypercholesterolemia (ICD-9 272.0) and diseases of other endocrine glands (ICD-9 249 – 250). There were statistically significant differences (p = <0.05) between groups for most comorbidities. Greater proportions of comorbid disorders (p = <0.0001) were reported in the commercial and MA cases for hyper- tensive disease, heart disease and endocrine disorders (Table 3). The commercial cases also showed a larger proportion of diseases of pulmonary circulation, which was statistically significant (p = 0.0008). There were no significance differences in pure hypercholesterolemia for either the commercial or MA populations. Overall, cases in both the commercial and MA populations were more likely (p = <0.0001) to have at least one co- morbid condition. Among the commercially insured, 1.6% of stroke cases had visited chiropractors within 30 days of being admit- ted to the hospital, as compared to 1.3% of controls visit- ing chiropractors within 30 days prior to their index date. Of the stroke cases, 18.9% had visited a PCP within 30 days prior to their index date, while only 6.8% of con- trols had visited a PCP (Table 4). The proportion of ex- posures for chiropractic visits was lower in the MA sample within the 30-day hazard period (cases = 0.3%; controls = 0.9%). However, the proportion of exposures for PCP visits was higher, with 21.3% of cases having PCP visits as compared to12.9% for controls (Table 5). The results from the analyses of both the commer- cial population and the MA population were similar (Tables 6, 7 and 8). There was no association between chiropractic visits and VBA stroke found for the
Table 3 Comorbid conditions Conditions n (%)
Commercial
Medicare
Cases (n = 1159)
Controls (n = 4633)
p-value Cases (n = 670)
Controls (n = 2680)
p-value <0.0001 <0.0001
Hypertensive disease
767 (66.2) 300 (25.9)
2078 (44.9)
<0.0001 554 (82.7)
1721 (64.2)
Ischemic heart disease
638 (13.8)
<0.0001 258 (38.5 )
563 (21.0)
Diseases of pulmonary circulation 29 (2.5)
55 (1.2)
0.0008 18 (2.7)
70 (2.6)
0.9140
Other forms of heart disease
357 (30.8)
800 (17.3)
<0.0001 306 (45.7)
713 (26.6)
<0.0001
Pure Hypercholesterolemia
9 (0.8)
24 (0.5)
0.2957 6 (0.9)
26 (1.0)
0.8590
Diseases of other endocrine glands 319 (27.5)
754 (16.3)
<0.0001 285 (42.5) <0.0001 593 (88.5)
740 (27.6)
<0.0001 <0.0001
At least one of the conditions
829 (71.5)
2317 (50.0)
1885 (70.3)
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