Epidemiological Research Designs

Epidemiological research is conducted to study the risk factors leading to disease or prevention (here, I use the word disease generically, as it could also mean a condition, such as low back pain). Epidemiologic designs are used because some questions cannot be answered by conducting clinical trials. For example, the best way to determine if smoking causes lung cancer would be to devise a clinical trial in which we randomize people into 2 groups, one who will smoke 3 packs of cigarettes per day for 5 years and one that does not smoke. At the end of the study, we could then compare cancer rates. But of course this is not ethical in any possible way. Rather, the epidemiological designs observe people as they live their lives, looking to see whether or not a risk factor may lead to a disease (or perhaps, in some case, to prevention. For example, does being active reduce the risk of heart disease).

There are three designs that are used in such studies. In order of increasing complexity, they are cross-sectional studies, case-control studies and cohort studies. They each work differently.

Cross-sectional studies: These look at the association of risk to disease. This kind of study is conducted at one point in time, the present. The most common form of cross-sectional study is a survey, in which we might ask a group of people if, for example, they have low back pain. Some percentage will say yes. We can also ask if they have a short leg. Some will say yes. What we cannot say is that these two are related in any way; this would require a more complex study. But we can demonstrate an association.

Case-control studies: Here, we begin with two groups of people in a population: those who have a condition of interest (i.e. cirrhosis) known as cases, and those who do not, known as controls. We then go “backward in time” reviewing their medical history to see if there is a higher exposure to a risk factor (i.e. heavy drinking) in the cases compared to the controls. In such studies, we can calculate an odds ration; that is, a comparison of the odds of developing a condition in the exposed group to the unexposed group. We cannot calculate risk because risk involves newly diagnosed cases, and we begin here with people already diagnosed.

Cohort studies: In the final and most complex kind of study, a cohort study follows a population of people forward in time to determine whether or not an exposure to a risk factor leads to a higher rate of a condition of interest. An example of a cohort study is the famous Framingham study, in which the people of Framingham, MA have been followed for nearly half a century to study the risk factors for cardiovascular disease. At the outset, no one has the condition; over time, as people live their lives, some will develop it. We then look at exposure to risk and compare the rate of disease in the group that was exposed to the group that was not. Because we are now looking for new diagnoses of disease, we can calculate actual risk rates and thus also a risk ratio: the risk of developing the condition in the exposed group divided by the risk in the unexposed group. This also allows us to determine incidence (number of new cases per population).

All of these designs are elegant in their own way, are less often seen in chiropractic, but are powerful tools for studying the relationship between risk and disease.

After Break Special: Three New Papers

Given we are all just returning from spring break, here are three new papers for you to peruse.

Oliver K, Innvar S, Lorenc T, Woodman J, Thomas J. A systematic review of barriers to and facilitators of the use of evidence by policymakers. BMC Health Services Research 2014, 14:2  doi:10.1186/1472-6963-14-2

ABSTRACT

Background: The gap between research and practice or policy is often described as a problem. To identify new barriers of and facilitators to the use of evidence by policymakers, and assess the state of research in this area, we updated a systematic review.

Methods: Systematic review. We searched online databases including Medline, Embase, SocSci Abstracts, CDS, DARE, Psychlit, Cochrane Library, NHSEED, HTA, PAIS, IBSS (Search dates: July 2000 - September 2012). Studies were included if they were primary research or systematic reviews about factors affecting the use of evidence in policy. Studies were coded to extract data on methods, topic, focus, results and population.

Results: 145 new studies were identified, of which over half were published after 2010. Thirteen systematic reviews were included. Compared with the original review, a much wider range of policy topics was found. Although still primarily in the health field, studies were also drawn from criminal justice, traffic policy, drug policy, and partnership working. The most frequently reported barriers to evidence uptake were poor access to good quality relevant research, and lack of timely research output. The most frequently reported facilitators were collaboration between researchers and policymakers, and improved relationships and skills. There is an increasing amount of research into new models of knowledge transfer, and evaluations of interventions such as knowledge brokerage.

Conclusions: Timely access to good quality and relevant research evidence, collaborations with policymakers and relationship- and skills-building with policymakers are reported to be the most important factors in influencing the use of evidence. Although investigations into the use of evidence have spread beyond the health field and into more countries, the main barriers and facilitators remained the same as in the earlier review. Few studies provide clear definitions of policy, evidence or policymaker. Nor are empirical data about policy processes or implementation of policy widely available. It is therefore difficult to describe the role of evidence and other factors influencing policy. Future research and policy priorities should aim to illuminate these concepts and processes, target the factors identified in this review, and consider new methods of overcoming the barriers described.

Kloek CJJ, Tol J, Veenhof C, van der Wulp I, Swinkels ICS. Dutch General Practitioners’ weight management policy for overweight and obese patients. BMC Obesity 2014, 1:2  doi:10.1186/2052-9538-1-2

ABSTRACT

Background: General practitioners (GPs) can play an important role in both the prevention and management of overweight and obesity. Current general practice guidelines in the Netherlands allow room for GPs to execute their own weight management policy.

Objective: To examine GPs’ current weight management policy and the factors associated with this policy.

Methods: 800 Dutch GPs were asked to complete a questionnaire in December 2012. The questionnaire items were based on the Dutch Obesity Standard for GPs. The data were analyzed by means of descriptive statistics and multiple linear regression analyses in 2013.

Results: In total, 307 GPs (39.0%) responded. Most respondents (82.9%) considered weight management as part of their responsibility for providing care. GPs aged <48 25="" 47.7="" a="" average="" bmi="" comorbidities="" compared="" dietitian="" discussed="" frequent.="" frequently="" gps="" is="" kg="" less="" m="" management="" moderately="" next="" obese="" of="" on="" or="" overweight="" patients.="" patients="" preferably="" professional="" refer="" reported="" sup="" the="" to="" weight-related="" weight="" with="" without="" years="">2

were less likely to refer obese patients. In addition, GPs who had frequent contact with a dietitian were more likely to refer obese patients. Conclusions: In the context of General Practice and preventive medicine, GPs’ discussion of weight and the variety of obesity-determinants with their moderately overweight patients deserves more attention, especially from younger GPs. Strengthening interdisciplinary collaboration between GPs and dietitians could increase the referral percentage for dietary treatment.

McClymont H, Gow J, Perry C. The role of information search in seeking alternative treatment for back pain: a qualitative analysis. Chiropr Man Ther 2014, 22:16  doi:10.1186/2045-709X-22-16

ABSTRACT

Background: Health consumers have moved away from a reliance on medical practitioner advice to more independent decision processes and so their information search processes have subsequently widened. This study examined how persons with back pain searched for alternative treatment types and service providers. That is, what information do they seek and how; what sources do they use and why; and by what means do they search for it?

Methods: 12 persons with back pain were interviewed. The method used was convergent interviewing. This involved a series of semi-structured questions to obtain open-ended answers. The interviewer analysed the responses and refined the questions after each interview, to converge on the dominant factors influencing decisions about treatment patterns.

Results: Persons with back pain mainly search their memories and use word of mouth (their doctor and friends) for information about potential treatments and service providers. Their search is generally limited due to personal, provider-related and information-supply reasons. However, they did want in-depth information about the alternative treatments and providers in an attempt to establish apriori their efficacy in treating their specific back problems. They searched different sources depending on the type of information they required.

Conclusions: The findings differ from previous studies about the types of information health consumers require when searching for information about alternative or mainstream healthcare services. The results have identified for the first time that limited information availability was only one of three categories of reasons identified about why persons with back pain do not search for more information particularly from external non-personal sources.

 

The Purpose and Processes of Evaluation

In Mary Weiner’s book “Learner-Centered Teaching” (1) there is a chapter that addresses the purpose and processes of evaluation. It notes that, as has always been the case, grading students is necessary and that students place great importance upon their grades. This is not surprising. But perhaps we need to look at this from a slightly different perspective: this may be an opportunity to help students learn. We should acknowledge the importance of grades, but harness their power to help in learning. To that end, Weimer offers some thoughts.

1.       First she suggests we harness the power of grades to motivate students. She notes that grades energize students. And she notes we can use that motivation for productive outcomes. We can do this be letting students know that learning matters more than grades. They still call the person who graduated last in your class “Doctor.” Meaning, later in life, whether you got an A or a B in a class may mean little.

2.       She next suggests we make the evaluation experience less stressful. The ability to harness grades to advance learning can be seriously diminished by increasing the stress associated with earning them. If I overhear one complaint in walking through the halls, it is about the stress people anticipate when facing certain examinations in the program. While stress can be good and useful for motivation, too much can be counterproductive to learning.

3.       She then states that evaluation should be used only to assess learning. It should not be used to help advance personal hidden agendas. An example of a hidden agenda is writing a harder test simply because you do not feel your students are taking your class seriously enough. If more than half a class fails an examination, it likely means the instructor is not doing a good job at explaining material, may not know how to write a good test, or that the test is simply be used for something other than enhancing learning.

4.       A final recommendation is to focus more on formative feedback. Are we suing our tests for this purpose. We may cover them in class, but are we doing so to meet a KPA or to truly help students understand what they missed and learn from that? How do we use the test to help them learn, fi we do not discuss it at all?

This is just food for thought and another way to look at an important question.

References

1.       Weimer M. Learner-centered teaching, second edition. San Francisco, CA; JOssey-Bass, 2013

New from Biomed Central

Nousiainen P, Merras-Salmio L, Aalto K, Kolho K. Complementary and alternative medicine use in adolescents with inflammatory bowel disease and juvenile idiopathic arthritis. BMC Compl Alternative Med 2014, 14:124 doi:10.1186/1472-6882-14-124

ABSTRACT

Background: The use of complementary alternative medicine (CAM) is potentially prevalent among paediatric patients with chronic diseases but with variable rates among different age groups, diseases and countries. There are no recent reports on CAM use among paediatric patients with inflammatory bowel disease (IBD) and juvenile idiopathic arthritis (JIA) in Europe. We hypothesized that CAM use associates with a more severe disease in paediatric IBD and JIA.

Methods: A cross-sectional questionnaire study among adolescent outpatients with IBD and JIA addressing the frequency and type of CAM use during the past year. The patients were recruited at the Children's Hospital, University of Helsinki, Finland.

Results: Of the 147 respondents, 97 had IBD (Crohn's disease: n = 46; median age 15.5, disease duration 3.4 years) and 50 had JIA (median age 13.8, disease duration 6.9 years). During the past 12 months, 48% regularly used CAM while 81% reported occasional CAM use. Compared to patients with JIA, the use of CAM in IBD patients tended to be more frequent. The most commonly used CAM included probiotics, multivitamins, and mineral and trace element supplements. Self-imposed dietary restrictions were common, involving 27.6% of the non-CAM users but 64.8% of all CAM users. Disease activity was associated with CAM use in JIA but not in IBD.

Conclusions: CAM use is frequent among adolescents with IBD and JIA and associates with self-imposed dietary restrictions. Reassuringly, adherence to disease modifying drugs is good in young CAM users. In JIA, patients with active disease used more frequently CAM than patients with inactive disease. As CAM use is frequent, physicians should familiarise themselves with the basic concepts of CAM. The potential pharmacological interaction or the toxicity of certain CAM products warrants awareness and hence physicians should actively ask their patients about CAM use.

Muller A. Teaching lesbian, gay, bisexual and transgender health in a South African health sciences faculty: addressing the gap. BMC Med Educ 2013, 13:174 doi:10.1186/1472-6920-13-174

ABSTRACT

Background: People who identity as lesbian, gay, bisexual and transgender (LGBT) have specific health needs. Sexual orientation and gender identity are social determinants of health, as homophobia and heteronormativity persist as prejudices in society. LGBT patients often experience discrimination and prejudice in health care settings. While recent South African policies recognise the need for providing LGBT specific health care, no curricula for teaching about LGBT health related issues exist in South African health sciences faculties. This study aimed to determine the extent to which LGBT health related content is taught in the University of Cape Town’s medical curriculum.

Methods: A curriculum mapping exercise was conducted through an online survey of all academic staff at the UCT health sciences faculty, determining LGBT health related content, pedagogical methodology and assessment.
Results: 127 academics, across 31 divisions and research units in the Faculty of Health Sciences, responded to the survey, of which 93 completed the questionnaire. Ten taught some content related to LGBT health in the MBChB curriculum. No LGBT health related content was taught in the allied health sciences curricula. The MBChB curriculum provided no opportunity for students to challenge their own attitudes towards LGBT patients, and key LGBT health topics such as safer sex, mental health, substance abuse and adolescent health were not addressed.

Conclusion: At present, UCTs health sciences curricula do not adequately address LGBT specific health issues. Where LGBT health related content is taught in the MBChB curriculum, it is largely discretionary, unsystematic and not incorporated into the overarching structure. Coordinated initiatives to integrate LGBT health related content into all health sciences curricula should be supported, and follow an approach that challenges students to develop professional attitudes and behaviour concerning care for patients from LGBT backgrounds, as well as providing them with specific LGBT health knowledge. Educating health professions students on the health needs of LGBT people is essential to improving this population’s health by providing competent and non-judgmental care.

Clar C, Tsertsvadze A, Coiurt R, Lewando Hundt G, Clarke A, Sutcliffe P. Clinical effectiveness of manual therapy for the management of musculoskeletal and non-musculoskeletal conditions: systematic review and update of UK evidence report. Chiropractic & Manual Therapies 2014, 22:12 doi:10.1186/2045-709X-22-12

ABSTRACT

Background: This systematic review updated and extended the "UK evidence report" by Bronfort et al. (Chiropr Osteopath 18:3, 2010) with respect to conditions/interventions that received an 'inconclusive? or 'negative? evidence rating or were not covered in the report.

Methods: A literature search of more than 10 general medical and specialised databases was conducted in August 2011 and updated in March 2013. Systematic reviews, primary comparative studies and qualitative studies of patients with musculoskeletal or non-musculoskeletal conditions treated with manual therapy and reporting clinical outcomes were included. Study quality was assessed using standardised instruments, studies were summarised, and the results were compared against the evidence ratings of Bronfort. These were either confirmed, updated, or new categories not assessed by Bronfort were added.

Results: 25,539 records were found; 178 new and additional studies were identified, of which 72 were systematic reviews, 96 were randomised controlled trials, and 10 were non-randomised primary studies. Most 'inconclusive? or 'moderate? evidence ratings of the UK evidence report were confirmed. Evidence ratings changed in a positive direction from inconclusive to moderate evidence ratings in only three cases (manipulation/mobilisation [with exercise] for rotator cuff disorder; spinal mobilisation for cervicogenic headache; and mobilisation for miscellaneous headache). In addition, evidence was identified on a large number of non-musculoskeletal conditions not previously considered; most of this evidence was rated as inconclusive.

Conclusions: Overall, there was limited high quality evidence for the effectiveness of manual therapy. Most reviewed evidence was of low to moderate quality and inconsistent due to substantial methodological and clinical diversity. Areas requiring further research are highlighted.