Chapter 1: Introduction and background
Since the previous systematic review search was carried out in 2007 by Hall et al. (2009) several new studies reporting on factors affecting adherence to a GFD have been published This update to Hall et al.’s (2009) systematic review identified 21 new studies. In this section, I present a brief discussion of the results of this systematic review. A fuller discussion of the results will be presented in the discussion chapter of this thesis along with the results of my concept mapping study.
In the systematic review by Hall et al. (2009) levels of strict adherence to a GFD was found to vary considerably (range = 42% to 91% adherence). In my update to Hall et al.’s (2009) review, I also found that adherence to a GFD was variable (range = 44.2% to 100% adherence). However, the one study that reported 100% adherence had an inclusion criterion that only allowed adherent participants to be recruited (Sey et al., 2011). Two other studies reported high levels of adherence to a GFD at 98% (Lee et al. 2012) and 96% (Black & Orfila, 2011). However, Lee et al. (2012) highlighted the fact that participants had over-estimated their level of adherence with a ‘surprising number’ later admitting to dietary transgressions. Similarly, a study by Leffler et al. (2008), which was included in the systematic review by Hall et al. (2009) found that participants tended to over-report their level of adherence to a GFD. It is likely that this over-estimation of adherence also occurred in other studies included in this systematic review. Further, it
is known that members of CD advocacy groups tend to be better at adhering to a GFD (Leffler et al., 2008). As several of the studies included in this and the previous systematic review recruited participants from coeliac advocacy groups, it is possible that the levels of adherence presented here are lower than those seen in the wider population of adults with CD. In addition, individuals who volunteer to take part in research may be more likely to be adherent to a GFD. Therefore, the true rates of non-adherence may be far higher than is reported in this systematic review.
This systematic review found no consistent relationship between adherence and demographic factors, which supports the findings from the previous systematic review by Hall et al. (2009). Education, age, gender, social class, employment status, marital status and ethnicity do not appear to be associated with adherence to a GFD. Further evidence is needed in relation to the association between smoking and adherence to a GFD.
Studies have examined a number of factors relating to knowledge and understanding in relation to adherence to a GFD. Being knowledgeable about the GFD and understanding the consequences of no-adherence appear to be associated with better adherence. However, no association was found between adherence to a GFD and understanding or reading food labels. There may be a need for better education in relation to CD and the GFD.
Personality traits and self-efficacy were associated with adherence to a GFD. Developing patients’ organisational skills, teaching them the skills
needed to confidently ask for GFF when eating away from the home may help to improve adherence to a GFD.
Interestingly, having trust in others to prepare GFF was associated with poorer adherence. The authors suggest this is related to being less vigilant in relation to avoiding gluten (Sainsbury et al., 2011).
Factors relating to illness and symptoms vary in their association with adherence to a GFD. No association was found between adherence and time since diagnosis, age at diagnosis, the presence of symptoms at diagnosis or the presence of symptoms when gluten is consumed. One study from the previous systematic review by Hall et al. (2009) reported that diagnostic delay was associated with adherence to a GFD. However, this is based on just one study and more evidence is needed.
Having an additional food intolerance may be associated with better adherence to a GFD. However, the reason for the association with adherence is not reported and further research is needed. Investigations into the association between body weight and adherence to a GFD suggest that obesity is linked with poorer adherence. This evidence is based on just one study, however, the study was judged to be of high quality and it included a large population (n=1018).
The provision of GFF on prescription in the UK is thought to make it easier for people with CD to follow a GFD (Coeliac UK 2013d). One UK study
reported that receiving GFF on prescription was associated with better adherence to a GFD. Although this evidence is based on just one study (n=287), it does support Coeliac UK’s argument against the recent cutbacks in prescribed GFF (Coeliac UK 2013b).
No association was found between adherence to a GFD and the duration of the GFD or perceiving the GFD to be difficult.
Healthcare professionals are responsible for providing the patients with information and advice at the time of CD diagnosis and it is recommended that patients are regularly reviewed after this time. The regularity of follow- up with healthcare professionals was associated with better adherence in this review and it is possible that healthcare for people with CD may need to improve in order to increase adherence to a GFD. This review did not find strong evidence of an association between adherence and satisfaction with the information received from healthcare professionals or attendance at a coeliac clinic.
Coeliac support groups are available in several countries and this systematic review provides strong evidence that membership to a support group is associated with better adherence to a GFD. However, the direction of causality is not known and it is possible that those people who are better at sticking to a GFD are more likely to join a coeliac support group than those who are non-adherent.
Travelling and eating away from the home can be problematic for people with CD and the evidence from my review shows that eating away from home is linked with poorer adherence. Poor awareness of CD by staff in restaurants (Karajeh et al., 2005) and poor availability of GFF when eating away from the home can make adherence to a GFD difficult. People with CD were reported to have difficulties with adhering to a GFD because it is restrictive with limited choice. These findings suggest that better provision of GFF is needed for people with CD when eating outside of the home. However, the availability of GFF was a factor that was not associated to adherence to a GFD.
Although it is claimed that the quality of GFF has improved in recent years, evidence from this systematic review highlights the ongoing dissatisfaction with the taste and texture of GFF and this is linked with poorer adherence. Olsson et al. (2008) found that the poor sensory qualities of GFF was linked with non-adherence in Australian adolescents. Patients are often unwilling to give up their favourite gluten-inclusive foods because they taste better than comparable GF products (Stuckey, 2008).
One of the barriers to adherence to a GFD may be the high cost of substitute gluten-free foods (Cureton 2007). The cost of speciality GFF is usually more expensive than gluten-inclusive equivalent foods (Lee et al., 2007) and the high price of GFF has been found to be associated with non- adherence to a GFD. In the UK, prescribed GFF is provided to patients with a CD diagnosis and this is believed to bring the cost of a GFD in line with a
gluten-inclusive diet. In this systematic review, one study that reported the high cost of GFF as a barrier to adherence was conducted in the UK. The other new studies that associated cost with adherence were conducted in the USA where GFF is not provided through the healthcare system.
Adhering to a GFD in the face of psychological problems, may be particularly challenging, however, the link between psychological symptoms and GFD adherence is tenuous. Contradictory evidence exists in relation to the association between depression and anxiety and adherence to a GFD. Although some studies found depression and anxiety to be related to poorer GFD adherence, the direction of causality is unknown.
Although several studies have reported on the relationship between QoL and adherence to a GFD, the evidence is contradictory and more research is needed.
This systematic review has some limitations. Nine different countries were represented in the studies included in this review. It is likely that people with CD will experience different problems associated with following a GFD depending on the country in which they the live. For example, some countries may provide better healthcare and resources for CD patients and this may affect the types of problems faced by people trying to follow a GFD. In the UK, GFF is provided on prescription, and this mitigates some of the costs associated with following a GFD. Furthermore, the availability
of GFF is likely to vary between countries. These differences could explain some of the conflicting findings reported in this systematic review.
Another limitation is the differences between how adherence to a GFD is assessed and defined. This makes it difficult to make comparisons between studies. The reliability of the methods of measuring adherence to a GFD was generally poor. Self-reported adherence is not regarded as a reliable measure, however, this method was used in several of the studies included in this and the previous systematic review. There is a requirement for further research to identify the true levels of adherence to a GFD using more reliable means of assessment. In addition agreement on what constitutes adherence to a GFD is needed.
Much of the research into the factors affecting adherence to a GFD in coeliac patients has produced conflicting results. In summary, this systematic review found that the factors affecting adherence to a GFD include knowledge and understanding of CD and the GFD, self-efficacy, organisational skills, the presence of additional food intolerances, body weight, the provision of GFF on prescription, membership of a coeliac advocacy group, eating away from the home and the cost and quality of GFF. I have been unable to find conclusive evidence about many of the factors reported in relation to adherence to a GFD and further studies are required. Additionally the relative importance of these factors to dietary adherence is not clear, thus making targeting of an adherence intervention
difficult, as it is impossible to currently know which factors have the greatest impact on adherence behaviours.
Chapter 3: Methods
“The best way to have a good idea is to have a lot of ideas”
Concept mapping is a mixed methods participatory approach that allows the views of participants from multiple stakeholder groups to be explored. In this study, participants were recruited from three stakeholder groups who were experienced in coeliac disease (CD): adults with CD; adults who live with them (household members); and healthcare professionals who work with adult coeliac patients.
In the first part of this chapter I provide a rationale for selecting concept mapping as an effective method for investigating the factors affecting adherence to a gluten-free diet (GFD). Comparisons are made between concept mapping and alternative methods that were considered for this study. In the remainder of this chapter I explain how the six-step concept mapping process was used to plan the study, gather and analyse the data and in interpreting the results.