Despite the historic emphasis on treatment, prevention and health promotion are receiving increased attention within the US health care system.1 These same health promotion tasks are considered by the National Academy of Science and others as essential components of health services delivered by primary care providers.² Chiropractors are viewed by many as capable of and actively delivering prevention and health promotion in addition to providing other primary care services. ^3–6

Prevention and health promotion activities administered by chiropractors are in 2 general categories: those considered orthodox by the medical community (eg, weight loss, exercise, smoking cessation) and those that are not (eg, soft-tissue and osseous manual procedures and some dietary supplementation). Previous research demonstrates that the orthodox activities used by primary care medical providers are also used by chiropractors. ^7–9 The nontraditional activities that rely on procedures such as spinal manipulation have not been investigated. The concept that chiropractic care is of value in maintaining health and preventing disease began with the work of Palmer.¹⁰ This preventive treatment is traditionally referred to as maintenance care (MC). MC has been defined as “a regimen designed to provide for the patient's continued well-being or for maintaining the optimum state of health while minimizing recurrences of the clinical status.”¹¹ Many chiropractors believe that periodic patient visits permit the doctor to identify joint dysfunction or subluxations and make corrections with spinal manipulation or other manual procedures. These treatments are believed to prevent disease of both neuromusculoskeletal and visceral origin.¹²

The purpose of this research is to explore the primary care prevention and health promotion attitudes and practice patterns of chiropractors, in particular the concept of MC, which has not been investigated in the United States. The study uses a common instrument for health care research, the postal questionnaire, and attempts to evaluate the therapeutic components believed necessary for maintenance patient care, the rationale for its use, what conditions respond most favorably, how frequently it is required, for which patients it is recommended, and its economic impact.

To identify information about chiropractic wellness and health promotion activities and the concept of MC, comprehensive literature reviews were conducted. This literature served the usual functions of assisting in creating the contextual background and search for possible similar work and guided the development of a survey instrument. Multiple online database searches including all years available in all languages were conducted through both Medline and Manual, Alternative, and Natural Index System (formerly Chirolars). Other databases were excluded because they either did not index chiropractic literature or the material indexed was redundant. Several search strategies were developed with the following Medical Subject Headings: chiropractic, health promotion, prevention, primary health care, and physician's practice patterns. In addition, manual searches were conducted through the Chiropractic Research Archives Collection and the Index to Chiropractic Literature as well as a limited manual search and bibliographic tracking. The search identified only a few studies related to the chiropractic physician's practice patterns directed at health promotion and prevention activities. With the exception of the development of a protocol and pilot study by Rupert et al,13 no other studies identified in the literature addressed the possible health promotion role of manipulation/adjustment or other manual procedures used by chiropractors. Although there has been some limited study of MC in Australia and to an even lesser extent in Europe, there has been no similar study in the United States. ^12,14

This descriptive study was conducted with a weighted randomized sample of US licensed chiropractors. A postal survey instrument was then mailed to the selected doctors. Sampling was conducted with the database of the National Directory of Chiropractic.¹⁵ The computerized version of the directory contains nearly 40,000 chiropractors who are in active practice. Unlike the hard copy version that is published annually, the computerized directory is updated continually. This database was used to create printouts and mailing labels based on zip code. Zip codes are created by the US Postal Service, with the first digit representing groups of states and the second and third subdividing the regions into smaller geographic areas. The final 2 digits are randomly assigned by the postal service and represent small post offices in rural areas or postal zones in larger cities.¹⁶ These final 2 numbers are randomly assigned by the postal service in such a manner that selecting a number would ensure selection from all states, with representation from rural areas and small and large cities. Selection with the ending numbers of the zip code would also ensure a “weighting” of the sample based on size of the state. The larger the state the more zip codes are used ending in the same number. The ending numbers to be used for selection from the computerized database were selected by a manual random drawing. This method helped ensure that chiropractors from each state and from rural areas and large cities were included in the mailing (but did not ensure their participation in the study). Such assurances would not have been possible with a pure random sample.

To obtain a sufficient sample size of US chiropractors for a confidence level of 0.05, 390 completed and returned surveys were required. This sample size was calculated in the same manner as described by Hawk and Dusio.⁷ The return rate of previous surveys of the profession has ranged from 20% to 60%. To ensure adequate response with an estimated response rate of approximately 30%, 1500 surveys were prepared and mailed.

Postal questionnaires are a well-established method for research. The chiropractic profession has a history of using these instruments for assessing the health promotion activities of chiropractors. ^7,12,13 No previous research questionnaire had been developed for investigating MC. The instrument used for this study was created by the principal investigator with the available literature on MC and discussions with practitioners. Revisions were made after use in a pilot study. Questionnaires from the medical literature were reviewed; key health promotion strategies, including exercise and smoking cessation, were included to determine if chiropractors believed these to be components of MC. To determine what chiropractors believed MC to be and to prevent biasing that process, no definition of MC was provided with the survey. Issues of questionnaire content, including length, manner of question design, and order of questions, were created with established conventions. ^17–19 The questionnaire developed for this research had a total of 40 questions. The first 5 were demographic questions followed by 35 questions related to MC. Of the 35 MC questions, 28 were developed with a 5-point ordinal Likert scale. With each question related to MC, the doctor could select 1 of the following responses: strongly agree, agree, undecided, disagree, or strongly disagree. The final 7 questions required short fill-in answers. Twenty-three of the questions related to 5 issues:

1. What is the purpose of MC? (6 questions)
2. Does the professional research adequately support MC? (2 questions)
3. What body systems/conditions respond best to MC? (6 questions)
4. What age groups of patients benefit most from MC? (4 questions)
5. What therapeutic interventions constitute MC? (5 questions)

The remaining 12 questions related to usage, economic issues, and other practice patterns.

Once the questionnaire content was established, it was administered to a convenience sample of 24 chiropractors. As a result of this pilot, minor modifications were made to some questions and the layout of the form. The revised questionnaire was kept to a single page with fields that could be checked in response to the Likert scale questions (Appendix 1). A special printed message on the outside of the envelope stated “Please contribute five minutes to professional research.” This notice was added to encourage a response and also to advise that it was not the typical solicitation that floods chiropractic offices. In addition to the questionnaire, a postage-paid envelope was included. To make follow-up possible, a number was assigned to each of the 1500 doctors selected to receive a survey. This number was placed on a master control list of the doctors and was kept by the principal investigator. The number corresponding to each doctor was also placed on the top of the questionnaire. Doctors were advised that their responses would be confidential.

There were 40 data points for each of the 658 returned surveys. This created a possible 25,920 data elements that were entered into a spreadsheet created by the principal investigator with Statistical Product and Service Solutions 7.5 for Windows. The person commissioned to enter these data had a history of accurate work and proofread questionnaire data after entry. In addition, the principal investigator performed a random review of data entry to ensure accuracy. SPSS was then used to create basic descriptive statistics, frequency distribution, tables, and related analysis.

Fig. 1. Purpose of MC.

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Fig. 2. Therapeutic composition of MC.

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Fig. 3. Value of MC for patient subsets by age.

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Fig. 4. Patients' response to MC condition/body system.

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There were 2 questions that addressed research. Only 40.2% agreed that adequate research existed to support the concept of MC and 93.4% agreed there was a need for more research (Fig 5).

Fig. 5. Research status and MC.

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Fig. 6. Miscellaneous questions.

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Based on the response to this survey, 78.7% of chiropractic patients are recommended for MC and 34.4% of those elect to receive these services. These patients average 14.4 visits annually for MC. Chiropractors estimated that 22.9% of their total practice income was generated from MC services (Table 2).

Postal surveys have inherent weaknesses but are a well-established form of biomedical research. One of the specific weaknesses in this study involves requesting chiropractors to provide the number of new patients per month, the percentage of income derived from MC, and other data that are not based on accurate counts and calculations but on estimates. In addition, the response rate (44%), although disappointing, was relatively strong for a chiropractic postal survey. Surveys within the profession rarely result in as much as a 50% response rate; previous survey response rates related to chiropractic and prevention have ranged from 22% to 65%. 7,12 A control number was assigned to each questionnaire to facilitate follow-up of nonrespondents. However, this did not prove effective because many doctors who did respond either obliterated, marked out, or actually tore off the number from the form to ensure anonymity. With the accuracy of written follow-up compromised, a selected follow-up was made by telephone. Eighty-five doctors for whom there was no record of a completed questionnaire were called and asked (1) if they completed the survey, (2) if they did not respond, why, and (3) if they used MC in their practice. Doctors indicated that the most common reason for nonparticipation was that they were too busy. The majority of nonrespondents also reported that they used some form of MC in their practices.

A review of the demographics of chiropractors who completed and returned questionnaires for this study did not vary significantly from other large contemporary surveys, with the exception of sex. The annual survey conducted in 1995 by the American Chiropractic Association reflected a sex mix within the profession of 88% men and 12% women.²⁰ The response to this MC study and previous prevention-related research conducted by Hawk and Dusio 7 both had a slightly higher percentage of female respondents than the national American Chiropractic Association survey (83% male and 17% female; 81% male and 19% female, respectively). Hawk and Dusio 7 indicated that the larger number of female respondents may reflect a bias.⁷ However, a recent medical study suggests that female physicians may have a greater interest in prevention activities than male physicians.²¹ This same phenomenon may in fact be operative within chiropractic and may account for the greater participation of women in this prevention-related survey. The average age of respondents in this study was 41 years compared with an average age of 44 years in the 1995 American Chiropractic Association survey.²⁰

Previous work outside the United States suggests that the use of MC accounts for a significant amount of services rendered by chiropractors. In England, Breen²² noted that after management for conditions like low-back pain, “39% of patients made further visits for maintenance treatment.” The Jamison¹² study of Australian chiropractors found that 62% performed MC on up to one third of their patients; 32% performed MC on 34% to 66% of their patients; and 6% performed MC on 67% to 100% of their patients.²³ This study attempted to address the same issues for chiropractors in the United States. Chiropractors were asked to provide the percentage of their patient load that received MC; the mean response was 34.4%. This suggests that a large percentage of chiropractic care given around the world is directed at prevention and health promotion. Shekelle²⁴ reported that 42.1% of patient visits to chiropractors were for low-back symptoms followed by 10.3% for neck/face symptoms. However, if as this study suggests, 34.4% of patient visits are for the purpose of MC, then preventive services may be the second most common reason for visits to a chiropractor. In addition to this high percentage of patients receiving MC, a much higher number, 78.7% of US patients, receive the recommendation to continue with preventive MC. This strong recommendation to receive preventive services suggests attitudes that are similar to Australian chiropractors: 41% asserted that everybody would benefit from such care, 38% believed that most would benefit, and 14% believed that some patients would benefit.¹²

Despite the emphasis by the US Government on initiatives such as Healthy People 2000,¹ the medical community continues to face many obstacles to providing preventive and health promotion services. ^25–28 With the use of MC to the extent described in this study, the chiropractic physician appears to place more emphasis on, derive more income from, and perhaps commit more patient time to prevention and health promotion purposes than many other health care professionals.

Another Australian study by Webb and Leboeuf¹⁴ found that there was a higher level of MC performed by doctors who had a lower number of new patients per month. The current research confirmed similar practice patterns (although number of MC visits was not ascertained) with a statistically significant inverse relation and correlation (P < .05) between the number of new patients per month and the practice income generated from MC.

In conjunction with the high percentage of patients who have been recommended for MC and the nearly half that comply, there also is a relatively high financial impact with an average 22.9% of all chiropractic income in the United States generated from these services. Based on an annual gross income of $225,783,²⁰ MC accounts for an average annual income of $51,930 per practice. When the 22.9% is viewed in the context of the total revenues of all chiropractors,²⁹ this would equate to $48 million in MC services delivered to US citizens during 1994.

It was not possible to be more specific about how patients paid for MC because of the necessity for reasonable brevity of professional surveys. Because most health insurance policies will not reimburse policyholders for health promotion services, future research should explore the methods of payment for MC.

A few authors have stated or implied that there are serious ethical issues with maintenance programs and that there is an inappropriate financial motive for what is termed “spurious” services. ^22,30 Homola³⁰ states that “It is unfair to patients to allow them to believe that they must have regular spinal adjustments in order to stay healthy.” Two findings from this survey suggest appropriate financial motive to MC services. First, the majority of the respondents (98%) agree that MC is of value for prevention and promoting the health of their patients. Twelve respondents, representing only 1.9% of the responding population, indicated that they never recommended MC. This consensus about the value of MC is remarkable considering the historical disagreement within the profession about so many other issues. In addition to the 98.1% of chiropractors recommending MC to their patients, 98% also agreed with at least 1 of the 6 questions describing the possible health benefits of MC. Chiropractors believe in the value of MC (98%) and therefore 98% recommend its use to their patients. Recommending the use of a procedure without belief in its value would suggest possible financial or other inappropriate motives, but this is not the case with MC. Secondly, 70.5% of chiropractors responded that they did not agree that MC was used for financial gain. Only 8.9% strongly agreed that MC was overused. The belief that MC was overused was significantly negatively correlated (P < .01), with both recommending MC to patients and the belief in the value of MC. Thus doctors who did not believe there was therapeutic value to MC (and did not or rarely recommended its use) were the ones who believed MC might be overused for financial gain.

This survey did find a significant inverse relation (P < .05) between the number of new patients per month and practice income from MC. However, the recommendation to receive MC was not related to practice income. There was also no correlation between income from MC and the doctors' belief that MC was of value in promoting health. These facts suggest that despite the number of new patients per month, chiropractors believe in the value of MC regardless of whether or not they are actually deriving income from MC services in their practices. It is possible that those chiropractors with lower patient loads are simply able to dedicate more time, and thus a higher percentage of their income is generated from MC services. Chiropractors, like all health care providers, must meet financial obligations and must charge for their services. It is reasonable to expect that they would focus on services for which they can expect reimbursement. MC, which is not covered in the United States by most health insurance, Medicare, or worker's compensation programs, is not one of those services. Therefore chiropractors with high volumes of patients with low-back pain and other reimbursable conditions might be less likely to spend as much time on services for which reimbursement is difficult, such as MC.

Previously, no data existed that described the therapeutic constituents of MC. Recently, there has been speculation by authors that chiropractors “keep people well through spinal adjustments”³¹ and that diet, exercise, lifestyle changes, and other prevention-directed activities are not part of the profession's prevention efforts. This view appears inaccurate because this study depicts the preventive MC activities of chiropractors as a combination of interventions that rely heavily on exercise, nutrition, and lifestyle changes. Although most doctors (96.7%) responding did agree that spinal manipulation was an essential component of preventive MC services, the respondents also agreed that exercise was an equally important component (96.1%), followed closely by proper eating (92.8%), patient education (83.6%), and vitamin and supplement usage (67.1%).

To ensure a response from field doctors, the questionnaire was only 1 page. Because of the short length of the questionnaire, there were only 4 age groups of patients listed: children, adolescents, adults, and the aged. The survey described a consensus about the value of MC for all 4 patient groups. This was a consistent response, considering the high percentage of patients recommended to receive MC. In addition, there is a prevalent belief that preventive MC services are helpful in a variety of visceral conditions and musculoskeletal problems. Because of the eclectic nature of the therapies used in MC and because it is standard medical practice to make exercise, nutritional, and other recommendations for many visceral problems, it is not surprising that chiropractors would also address these conditions. It was beyond the scope of this initial study to ascertain to what extent chiropractors believe specific visceral and musculoskeletal conditions benefit specific therapeutic components of MC. Five different purposes for MC were given with this survey. Relatively strong agreement was found for all but 1 (ie, the prevention of subluxation). Slightly more than half of chiropractors believed MC was valuable for this purpose. This response raises questions about the belief system of chiropractors because it relates to prevention and the subluxation concept. If MC cannot prevent subluxation, how is it prevented? Future studies should be directed at exploring wellness and prevention in the context of subluxation.

The 658 doctors who responded to the survey were relatively unaware of the scarce research that supports the use of MC. Forty percent believed that “chiropractic research adequately supports the value of MC” and <7% strongly disagreed with that statement. This misconception exists despite the fact that the deficiency in supporting research has been brought to the profession's attention on many occasions by both the medical community and those involved in chiropractic research. ^32–35 The survey did establish that the overwhelming majority (93.4%) of the profession agreed that there was a need for further research. The research issue questions the education of chiropractors as it relates to MC. Future research should be directed at why there is such a strong belief in the value of the spinal manipulation component of MC among both new and established chiropractors. In what manner is this subject addressed in chiropractic colleges and to what extent does practice experience have an impact on the belief in MC? One reason why chiropractors may believe that adequate research exists is simply because, as this survey suggests, MC includes a wide variety of well-researched health promotion components, including exercise, food supplementation, and diet.