A Critical Review of the Literature

Jon Adams, PhD, Gaery Barbery, MPH, Chi-Wai Lui, PhD

Headache. 2013;53(3):459-473.

Abstract and Introduction

Abstract

Contexts.—An evidence base for complementary and alternative medicine (CAM) consumption within general populations is emerging. However, research data on CAM use for headache disorders remain poorly documented. This paper, constituting the first critical review of literature on this topic, provides a synopsis and evaluation of the research findings on CAM use among patients with headache and migraine.

Methods.—A comprehensive search of literature from 2000 to 2011 in CINAHL, MEDLINE, AMED, and Health Sources was conducted. The search was confined to peer-reviewed articles published in English reporting empirical research findings of CAM use among people with primary headache or migraine.

Results.—The review highlights a substantial level of CAM use among people with headache and migraine. There is also evidence of many headache and migraine sufferers using CAM concurrent to their conventional medicine use. Overall, the existing studies have been methodologically weak and there is a need for further rigorous research employing mixed method designs and utilizing large national samples.

Discussion.—The critical review highlights the substantial prevalence of CAM use among people with headache and migraine as a significant health care delivery issue, and health care professionals should be prepared to inquire and discuss possible CAM use with their patients during consultations. Health care providers should also pay attention to the possible adverse effects of CAM or interactions between CAM and conventional medical treatments among headache and migraine patients.

Introduction

The use of complementary and alternative medicine (CAM) – a diverse group of health care practices and products not traditionally associated with the medical profession or medical curriculum ^[1] – has increasingly become a mainstream health care activity in Western societies. ^[2–6] In recent years, CAM has become an issue of growing importance for health care practitioners as well as policy makers. ^[1,7,8]

Over recent decades, an evidence base for CAM consumption within general populations has emerged. ^[9–13] However, research data on CAM use for specific health or clinical conditions remain less well documented, and the use of CAM specifically for headache and migraine is no exception. This paper provides the first critical, systematic examination of the evidence base of this crucial health care issue, synthesizing empirical research findings and highlighting a number of gaps and challenges facing future research in this increasingly important practice area.

Headache and Migraine: The Significance of Exploring CAM Use

Headache and migraine is a very common health condition, and according to the International Headache Society, the percentage of the global adult population with an active general headache disorder is 46%, with 11% suffering from migraines, 42% suffering tension-type headaches, and 3% suffering chronic daily headache. ^[14] A systematic review has identified the global prevalence of chronic migraine at 0–5.1%, with estimates typically in the range of 1.4–2.2% of the general population. ^[15] The impact of headache disorders is substantial, and the World Health Organization ranks headache disorders as some of the most disabling conditions for both men and women. ^[14] Given the substantial effect of headache and migraine on the quality of life of the sufferer and the significant disruption to work, family, and social duties, ^[16–18] it is imperative that all effective headache and migraine treatments be explored and researched.

Conventional medical intervention for headache and migraine often involves pharmacological treatment. Acetaminophen (paracetamol), acetylsalicylic acid (aspirin), dipyrone, derivatives of ergot fungus, chlorpromazine, triptans (Imitrex/Imigran, et al), and non-steroidal anti-inflammatories are the most commonly prescribed drugs for the acute treatment of headache and migraine. ^[19] Tricyclic antidepressants, β-blockers, and anti-epilepsy drugs are the most commonly prescribed and best evidence-based classes of pharmacologic preventative interventions for episodic migraine. ^[20] Despite many patients reporting benefits from these drug treatments, the pharmacological interventions are not without their limitations or side effects. For instance, amitriptyline, one of the most widely used preventive antimigraine agents, has side effects ranging from drowsiness, dry mouth, constipation, and weight gain to the possibility of precipitating cardiac arrhythmias, seizures, or exacerbating closed-angle glaucoma. ^[19] In addition, headache and migraine are often long term, with relapses and remissions that create continuing distress and disruption to patients’ daily lives. ^[16]

The treatment of headache and migraine is one area of health care where CAM treatment shows some promise. ^[21–28] Nevertheless, the benefits and risks of CAM in treating and managing headache and migraine disorders remain contested, and a recent systematic assessment of the evidence base of CAM treatment for primary headache found that the overall quality of research of CAM approaches still lags behind studies of conventional medical approaches to primary headache. ^[29]

Results from large cohort/population studies suggest that CAM use is common among headache and migraine patients. For instance, a US study on symptoms and conditions among CAM users in a large military cohort (n = 86,131) suggested that about 10% of the respondents reported the problem of migraine headache and the study suggested this condition is more likely to be reported by CAM users than by people not using CAM. ^[30] Analysis of the US National Health Interview Survey (n = 31,044) also identified headache as one of the most common health problems experienced by CAM users. ^[31] While these studies highlight a relationship between CAM use and headache disorders, they provided little information on the patterns of and motivations for CAM use among people with headache and migraine.

Although evidence of CAM use for headache and migraine is emerging, there has been no review or synthesis of CAM user characteristics, perceptions, or motivations among headache and migraine sufferers. Such a review is essential in order to provide important insights for health practitioners and policy-makers with regard to the safety and continuity of care for patients – an issue pronounced by the fact that CAM users appear not to disclose such use to their conventional doctors. Previous studies reveal that a lack of general practitioner (GP) interest in their patients’ use of CAM or the patients’ perception that CAM use is not an important issue that should be raised with their doctor are the 2 major factors contributing to nondisclosure of CAM. ^[32–34] In response, this paper provides the first synopsis and evaluation of the research findings on CAM use among patients with headache and migraine as identified from recent international empirical literature. Specifically, this paper aims to: (1) identify the relevant studies that examine the use of CAM among people with headaches; (2) analyze the quality of these studies; and (3) summarize the key findings from these studies using theme-based analysis.

Methods

Design

The aim of the review is to examine the current prevalence, pattern, and details of CAM use among people with headache and migraine. A comprehensive search of the literature between 2000 and 2011 was undertaken in line with the exponential growth in CAM use and growing research attention upon this topic over the past decade. The CINAHL, MEDLINE, Health Source, and AMED databases were searched, using the following key terms and phrases: complementary medicine/therapy, alternative medicine/therapy, natural medicine/therapy, holistic medicine/therapy, headache, primary headache, migraine, cephalalgia, cephalgia, cranial pain, and hemicrania. The CINAHL, MEDLINE, and Health Source are 3 of the most popular, comprehensive databases for health and medicine scholarship. The AMED database was also chosen as an authoritative resource on allied health and complementary medicine scholarship. The database search was confined to peer-reviewed articles published in English.

To ensure all relevant international literature was identified, the authors also conducted hand searches in prominent headache and migraine journals including Headache, Cephalalgia, and Journal of Headache and Pain. Relevant works were also identified by examining bibliographies of publications.

The search results were imported into Endnote, ^[35] a bibliographic management system software program, with all duplicated items removed. The remaining titles and their abstracts were screened and assessed independently by 2 authors who employed the following criteria to identify relevant studies for inclusion in the review: Peer-reviewed, research-based papers reporting new empirical findings focusing upon either CAM use among people with primary headache or migraine, or CAM use among a broader population or general population where CAM use among headache and/or migraine patients was clearly identifiable and extractable.

Those papers identified as individual case reports or CAM clinical trials were excluded from the review. In those circumstances where the abstract was deemed to not provide sufficient information, the full article was retrieved and examined prior to a final decision regarding inclusion or exclusion status.

Search Outcomes

The initial search identified 565 papers, and a total of 14 articles met the selection criteria. Two of these 14 articles ^[36,37] were subsequently eliminated due to the reporting of the findings of surveys that were already covered elsewhere. ^[38,39] As a result, a total of 12 papers were included in this review. The Figure reports the literature search process, and summarizes the basic details of the included papers.

 

 

Quality Appraisal

In order to appraise the quality of the papers identified for review, the authors employed a quality scoring system () drawing upon quality assessment tools previously used for assessing prevalence studies on low back pain ^[50] and CAM use among cancer patients. ^[51,52]The use of these established analytical tools allowed for systematic comparison and evaluation of the CAM surveys reviewed.

Two authors assigned scores to the studies separately; the results were then compared and disagreements and differences resolved by discussion. reports the quality score of each individual study.

Results

The context and findings of the 12 papers were extracted, grouped, and summarized using an integrative review approach. ^[53,54] The data extracted were synthesized using the following themes: the prevalence of CAM use, user profile and predictors of use, motivation and perception of CAM use, and referral and disclosure of CAM use.

The Prevalence of CAM Use

The 12 papers selected for review reported a wide range of prevalence rates for CAM use among people with headache and migraine (refer to ). For instance, an analysis of national health survey data identified 50% of US adults with migraines or severe headaches as using at least one CAM over the past 12-month period. ^[39] A similar analysis in Canada discovered that 19% of people with migraine visited a CAM practitioner in the last 12 months. ^[43] A large cross-sectional cohort study among patients of tertiary headache centers in Austria and Germany found that 82% of the respondents had used CAM at some stage in their lifetime. ^[38] Three studies conducted in Italy on patients with different types of headache disorders reported CAM use rates of 31% (among patients with migraine), 40% (among patients with chronic tension-type headaches), and 29% (among patients with cluster headaches). ^[44–46] Meanwhile, another survey of adults in Croatia identified 28% of respondents with headache disorders had used CAM (lifetime prevalence). ^[49] Despite these variations in findings, the studies do indicate relatively substantial prevalence of CAM use among people suffering from headache and migraine.

There are several factors that may account for the differences in reported prevalence of CAM use. First of all, the differences may reflect variations in study or sample design with different studies targeting different populations or types of headache/migraine patients. For instance, patients in the general population may be different from patients presenting in headache-specific clinics. In addition, studies have adopted different definitions of CAM which may also contribute to the differences in reported prevalence rates. For example, Rossi et al ^[44] defined CAM as “a wide range of pharmaceutical-type and non-pharmacological therapies that do not, on the whole, fall within the sphere of conventional medicine.” In contrast, Lambert et al ^[42] adopt a definition of CAM in their study that was “essentially respondent-defined,” and Metcalfe et al ^[43] confined their analysis of CAM use to visits to CAM practitioners. Finally, the variation in ways of measuring CAM use (eg, lifetime use or use in the past year) is another factor that renders the interpretation and comparison of prevalence estimates between studies of a particular challenge.

Acupuncture, massage, chiropractic, and homeopathy were the most common therapies reported as used by those suffering from headache and migraine in the studies reviewed. The findings of a large national representative survey suggested that mind–body therapies such as meditation, breathing exercise, and yoga were the most common CAM used by US respondents with migraines or severe headaches. ^[39] There is evidence that a majority of CAM users seek CAM concurrent with (ranged from 7% to 30%) or following (ranged from 64% to 93%) a GP visit. ^[42,44–46] In contrast, only a small proportion of respondents (ranging from 5% to 19%) used CAM before they visited a doctor. ^[42,44–46] Lambert et al ^[42] also found that 80% of their study respondents did not relinquish their use of prescribed medications while consuming CAM. Together, these results suggest that CAM is likely used as a complementary (alongside) rather than an alternative treatment (as a replacement) to conventional medicine among people with headache and migraine.

CAM User Profile and Predictors of CAM Use

The sociodemographic characteristics of headache and migraine sufferers who use CAM are similar to the profile of CAM users identified in the general population. ^[9,12] Specifically, people with headache and migraine who use CAM are more likely to be female,^{[38,39,42,44–48]} be married, ^[44–46,48] have a higher education level, ^{[38,39,42,44–46,48]} report a higher annual income, ^{[38,39,44–46]} and be full-time employed. ^[42,44–47]

Research evidence indicates that the seriousness of headache conditions (in terms of number of headache days, duration of headache treatment, or frequency of GP/specialist consulted) is an important factor that determines CAM consumption; people with more severe headache conditions are more likely to use CAM. ^[38,43–46] Lambert et al ^[42] also found that a Headache Impact Test score − a widely used tool to measure the impact of headaches on a person’s ability to function on the job, at home, at school, and in social situations − is of significance as a predictor of CAM use. In addition, analysis of data from the 2007 National Health Interview Survey indicates that other health conditions or lifestyle characteristics such as a history of anxiety, joint or low back pain, and alcohol use are independently associated with higher CAM use among patients with migraines or severe headaches. ^[39]

Motivations for and Perceptions of CAM Use

summarizes the findings regarding motivations and perceptions of CAM use from the 12 studies selected for review. Wells et al ^[39] identified that headache and migraine patients who employed CAM perceived conventional treatment as ineffective more often than those who did not use CAM, and a national representative survey in the USA revealed that 39% of those people who consulted a doctor and used CAM considered CAM as more effective than conventional medicine in treating headache. ^[41] However, findings from other studies indicate that only a small portion of headache and migraine patients sought CAM in response to a bad experience or dissatisfaction with their conventional treatment. ^{[38,42,44–46]}

The most common reasons for CAM use as identified by Gaul et al ^[38] were “to leave nothing undone” (64%) and “to be active against the disease” (56%). This study also found that other considerations like “anxiety of side effects [of conventional treatments]” (20%) and “request for a therapy without side effects” (31%) were also important in headache and migraine patients seeking CAM. Lambert et al ^[42] found that 48% of their respondents chose to use CAM “as a last resort.” The 3 Italian studies by Rossi et al ^[44–46] identified a belief among patients that CAM was “potentially beneficial for headache” (about 45%) or CAM was “safer and [with] less side effects [than conventional treatments]” (about 27%) as major reasons for CAM use. In contrast, the analysis of the US national health survey data reveals that while nearly half of adults with migraines or severe headaches use CAM, only about 5% of them use CAM to specifically treat their headache/migraine symptoms. Instead, the main reasons of using CAM as reported in this study were “general wellness/disease prevention” and “to improve/enhance energy.” ^[39]

Previous study findings indicate that perceptions of CAM effectiveness are mixed among headache and migraine patients who are CAM users. Lambert et al ^[42] explain that 60% of respondents report CAM as reducing/greatly reducing their headache and 58% were satisfied with the therapy used. von Peter et al ^[48] also found that 60% of the headache patient population interviewed perceived CAM as of potential benefit for the treatment and relief of headache.

However, the 3 surveys conducted by Rossi et al ^[44–46] reveal that over half of respondents (ranging from 57% to 59%) experienced CAM as ineffective in the treatment of their headache disorders and this was particularly the case among those with migraine (73.1% reporting CAM as being ineffective). ^[44] In addition, about 5% of respondents in 2 of these Italian studies reported CAM treatment as resulting in a deterioration of their condition. ^[44,46] Finally, Vukovic et al ^[49] report that satisfaction with CAM varied among patients suffering from different kinds of headache conditions, with 39% of patients with migraine, 60% of patients with tension-type headache, and 41% of patients with probable migraine and tension-type headache reporting satisfaction with their CAM treatment.

Referral to and Disclosure of CAM Use

A review of the research literature identifies 3 key sources utilized by people with headache and migraine to gain information about CAM. A substantial proportion of headache and migraine patients using CAM (ranging from 41% to 72%) obtain information about CAM from their acquaintances or relatives. ^[42,44–46] The patients’ doctor or nurse was the second common referral source through which headache and migraine patients became familiar with CAM (ranging from 16% to 34%) and a relatively small proportion of headache and migraine patients (ranging from 4% to 20%) relied solely upon their own judgment with regard to using these treatments. ^[42,44–46]

In line with findings from studies of general CAM users, ^[32] headache and migraine patients utilizing CAM do not commonly inform their doctor or nurse about such CAM use. Wells et al ^[39] discovered that although CAM users with migraine or headache had a higher disclosure rate than those without migraine or headache, less than half (47%) discuss their CAM use with their conventional health care provider(s). The 3 surveys conducted in Italy by Rossi et al ^[44–46] identify over 60% of respondents as failing to disclose their CAM use to their conventional doctor. Meanwhile, Soon et al ^[47] reveal that only 16% of headache and migraine patients in Singapore using CAM informed their doctor or specialist about such use.

In contrast, Lambert et al, ^[42] examining headache and migraine patients in the UK, report 58% of their respondents as disclosing CAM use to their doctor or nurse. However, the same survey also discovered that 80% of respondents report their doctor or nurse as never inquiring or initiating discussion with them about CAM use. Rossi et al ^[44] also questioned their respondents about their reasons for failing to inform conventional doctors about their CAM use. In response, 37% of the migraine patients reported that their doctors never ask for this information and 50% of them considered CAM use as a matter either “not important for the doctor to know” or “none of the doctor’s business.”

Discussion

This paper provides the first critical, comprehensive review of the evidence base of CAM use and users among people suffering from headache and migraine. The use of CAM among patients with headache and migraine is an issue that has increasingly attracted the attention of practitioners and researchers over the past decade, ^[28,55,56] as reflected by the review findings with the bulk of empirical studies (10 out of the 12 studies identified over the last 11 years) having been published since 2005.

Although the evidence base focused upon CAM use among headache and migraine patients has begun to emerge, the ability of this review to generalize from studies or compare findings across studies remains difficult with variations in research design and the definition of CAM employed between studies of particular challenge. This is a problem that also plagues the assessment of clinical outcomes of CAM therapies on treating primary headache. ^[29] In addition, this review is confined to English language publications and the omission of non-English materials may introduce some bias.

Despite these limitations, the evidence identified and examined in this review does, nevertheless, suggest a substantial level of CAM use among people with headache and migraine. There is also evidence of many headache and migraine sufferers using CAM concurrent to their conventional medicine use (as a complement rather than alternative), a finding consistent with survey results of CAM use in the broader general population. ^[9,57]

The frequent use of a range of CAM among people with headache and migraine warrants further investigation. There is evidence that many people use CAM as a follow-up treatment or last resort in an attempt to relieve their headache and migraine symptoms. In contrast, recent findings of a large national health survey indicate that only a small proportion of people with migraines and severe headaches use CAM specifically for the treatment of their headache conditions. ^[39] The coexistence of a high CAM usage with the fact that a substantial proportion of users consider CAM ineffective in treating their headache symptoms is also interesting. ^[44–46] In short, the role of CAM in treating headache and migraine symptoms or helping patients to cope with their distress in their everyday lives remains unclear. There is a need for further in-depth qualitative studies on the motivations, experiences, and perceptions of CAM use among headache and migraine sufferers.

The prevalence of CAM use among headache and migraine patients also has implications for conventional health care providers. Because the prevalence rate of CAM is high among headache and migraine patients and a substantial percentage of these patients appear to not disclose their CAM use to conventional practitioners, health care professionals should be prepared to inquire and discuss with their patients about possible CAM use. Relevant health care providers should also pay attention to the possible adverse effects of CAM or interactions between CAM and conventional medical treatments among headache and migraine patients. This is important given a very small minority of headache and migraine patients who utilize CAM report deterioration in their condition. ^[44,46]

In light of this review, it is possible to identify areas for future research attention pertaining to headache and migraine patients and CAM use. As the quality scores reported in indicate, the studies examining this topic to date have been methodologically weak. Only 2 of the studies attracted a sample size over 500, with only one of them employing a nationally representative sample. As such, there is a pressing need for rigorous studies examining this important field of CAM use and user research, employing mixed method designs and utilizing large and/or representative national samples where possible.

Meanwhile, given that all previous research have utilized cross-sectional study design, there is also a need for longitudinal studies to examine changes in CAM use in accordance with changes in conventional treatments and severity of the headache disorders and throughout different stages of the headache and migraine patient’s illness and treatment journey.

While remaining mindful of cultural contexts and variations in CAM, researchers are also recommended to adopt a common taxonomy or classification of CAM practices/exposures in self-reported descriptive surveys of CAM use for headache and migraine where possible.^[58] This will help address challenges resulting from rapid developments regarding evidence and institutional approvals. For example, Petasites hybridus, or butterbur root, was recently found to have level A evidence for proof of benefit in episodic migraine by the Quality Standards Subcommittee of the American Academy of Neurology and the American Headache Society. ^[20] As the evidence base demonstrates, the use and satisfaction with CAM varies among patients suffering from different kinds of headache and migraine. ^[49] Future research will benefit from differentiating and/or targeting patients suffering from different and specific types or severities of headache and migraine. Together, these design features will strengthen the evidence base of CAM use on this topic and provide a much better picture of CAM consumption for the treatment of headache and migraine.

Conclusion

The use of CAM appears to constitute a treatment option considered and employed by a substantial proportion of patients suffering from headache and migraine. This review has provided essential insights into the prevalence and details of CAM use and related issues among headache and migraine patients with implications for practitioners (both conventional and CAM) and health policy makers. It is recommended that further research utilizing both quantitative and qualitative methods be undertaken to address a number of important issues still requiring attention and essential to helping a range of stakeholders provide effective, safe, and responsive care and services for those suffering from headache and migraine.