Factors affecting adherence to a gluten-free diet

In document Gluten-free diet adherence in adult coeliac disease: Exploring multiple perspectives (Page 90-115)

Chapter 1: Introduction and background

2.4 Results

2.4.4 Factors affecting adherence to a gluten-free diet

This update to the systematic review by Hall et al. (2009) has identified a number of new factors associated with adherence to a GFD. The studies included in this update varied in the number of adherence factors they identified. Appendix 3 shows a list of the factors with details of the studies that identified each adherence factor. Hall et al. (2009) grouped the factors associated with adherence to a GFD identified in their study into six themes. In the following six sections, I present the results of my update of Hall et al. (2009) systematic review using the same six themes. I have also included the results of the systematic review by Hall et al. (2009) to provide an overall summary of the evidence.

Tables 2.5 to 2.10 show the results of my analysis along with the results of the quality assessment for each study included in this review. I have reported the quality of the papers used in Hall et al.’s (2009) systematic review as moderate/high which reflects the decision by the authors to exclude papers that were judged to be of poor quality from their review. I have included papers from my update to Hall et al.’s (2009) systematic review that I judged to be of low quality, however, I have taken into account the limitations of these studies when interpreting the results.

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Sociodemographic factors

Table 2.5 shows the results of the analysis for studies that report on sociodemographic factors in relation to adherence to a GFD. All of the studies that assessed sociodemographic factors were judged to be of moderate or high quality except for one low quality study (Lee et al 2012). The results of this study were in line with all of the other new studies results which report that gender is not associated with adherence to a GFD, so it was judged that the result was probably trustworthy.

Hall et al. (2009) identified two studies that reported education as a factor that was associated with adherence to a GFD, but five where it was not. I identified a further two studies, one reported better adherence in people with a university education (Barratt et al. (2011) but the other study (Hall et al., 2013) found no association. Therefore, education does not have a consistent relationship with adherence to a GFD.

Age was identified by Hall et al. (2009) as a factor that was associated with adherence in three studies, and not associated in a further seven studies. I identified three more studies which found an association with age (n=1124), and four that did not (n=3437). The three studies that found an association between age and adherence to a GFD, all reported that older age was associated with better adherence. Overall, age does not appear to have a consistent relationship with adherence.

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Hall et al. (2009) identified just one study that associated gender with adherence and seven studies that did not. I identified a further five studies (n= 4745) that showed no association of gender with adherence. Overall, the evidence suggests that gender is not associated with adherence to a GFD.

No association was found between social class and adherence to a GFD in two studies included in the systematic review by Hall et al. (2009). I identified one more study that showed an association with having an affluent background. Social class does not appear to have a consistent relationship with adherence.

Hall et al. (2009) identified one study (n=234) that showed an association with urban living with adherence. I identified no further studies that examined this factor. Overall, there is weak evidence for an association of urban living with adherence.

Hall et al. (2009) identified two studies that showed no association of employment status with adherence, and I did not identify any additional studies. Therefore overall there is evidence that employment status is not associated with adherence.

One study (n=154) identified in the systematic review by Hall et al. (2009) showed marital status was associated with adherence. I identified one more study (n=255) that showed no association between marital status and

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adherence. Therefore, marital status does not have a consistent relationship with adherence to a GFD.

Hall et al. (2009) identified one study (n=87) that showed ethnicity was associated with adherence, but I identified one larger study (n=679) that showed no such association. Therefore overall it is unlikely that ethnicity is associated with adherence to a GFD.

Finally I identified one study (n=204) that showed smoking status was associated with adherence. This single study provides weak evidence that non-smokers have better adherence to a GFD. Overall there is little evidence that any of the sociodemographic factors associate with adherence behaviours.

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Table 2.5 Sociodemographic factors (including results from Hall et al.’s

(2009) systematic review)

Authors Adherence factor Number of

participants in studies that show an association with adherence

Number of participants in studies that did not show an association with adherence

Assessment of quality

Hall et al., 2009 Education 2/71 (n=971) 5/71 (n=566) Moderate/High Barratt et al., 2011 Education (university

education is

associated with better adherence)

n = 573 Moderate

Hall et al., 2013 Education n=287 Moderate Hall et al., 2009 Age 3/101 (n=673) 7/101 (n =1132) Moderate/High Barratt et al., 2011 Age n=573 Moderate Casellas et al. 2012 Age n=1898 High Ford, 2012 Age (older age is

associated with better adherence)

n=228 Moderate

Hall et al., 2013 Age n=287 Moderate Hopman, 2009 Age (older age is

associated with better adherence)

n=53 Moderate

Kabbani et al., 2012 Age n=679 High Kurppa, 2012 Age (older age is

associated with better adherence)

n=843 High

Hall et al., 2009 Gender 1/71 (n=128) 6/71 (n=1806) Moderate/High Barratt, 2011 Gender n=573 Moderate Hall, 2013 Gender n=287 Moderate Hutchinson, 2010 Gender n=284 High Kabbani et al., 2012 Gender n=679 High Lee et al., 2012 Gender n=2922) Low Hall et al., 2009 Social

Class/socioeconomic status

2/21 (n=282) Moderate/High Barratt et al., 2011 An affluent

background/wealthy achievers show better adherence

n=573 Moderate

Hall et al., 2009 Urban residence 1/11 (n=234) Moderate/High Hall et al., 2009 Employment status /

Occupation

2/21 (n=544) Moderate/High Hall et al., 2009 Marital status 1/11 n=154 Moderate/High Barratt et al., 2011 Marital status n=225 Moderate Hall et al., 2009 Ethnicity 1/11 (n=87) Moderate/High Kabbani, 2012 Ethnicity n=679 High

Errichello, 2010 Non-smokers had better adherence

n=204 Moderate

Note:

1. The figures shown here indicate the number of studies included in the systematic review by Hall et

al. (2009) in relation to a particular adherence factor. For example, for ‘Education’ two out of seven

(2/7) studies from the Hall et al. (2009) systematic review showed an association between education and adherence to a GFD and five out of seven (5/7) studies showed no association between adherence

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Knowledge, attitudes and beliefs

Table 2.6 shows the results of the analysis for studies that report on knowledge, attitudes and beliefs in relation to adherence to a GFD. All of the factors relating to knowledge, attitudes and belief were identified in just five out of the 21 studies included in this systematic review update. There may be issues of the same or similar factors being labelled differently by different authors. I have grouped factors together in a way that seemed logical to me.

Hall et al. (2009) and I both identified one study each that identified knowledge and understanding of a GFD as being associated with better adherence. One new study showed that improved awareness and understanding were believed to make adherence to a GFD easier. Therefore, it appears that knowledge and understanding is associated with better adherence to a GFD.

Hall et al. (2009) identified two studies that investigated the association between reading food labels and adherence to a GFD. One of these studies was associated with adherence to a GFD and the other was not. In my update, I found one further study (N=278, low quality) that found reading food labels to be associated with better adherence to a GFD.

Hall et al. (2009) found a study showing an association between adherence to a GFD and beliefs about the harm of exposure to gluten. Two new studies

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showed evidence of association between worry about the long term impact of the disease with adherence and another new study showed no association. One new study showed an association between having a low belief in the cyclical nature of CD and better adherence to a GFD. Overall, it appears that beliefs about the seriousness of the consequences of non-adherence are associated with adherence to a GFD.

A high quality study by Edwards-George (2009) (N=154) examined personality traits and found that higher conscientiousness, values, order, self-discipline and deliberation traits were all associated with better adherence. Another study by Sainsbury (2013a), which was larger (n=390) but of moderate quality, identified that intention to adhere, task orientated coping and emotion orientated coping were all associated with improved adherence to a GFD. Overall, it appears that personality trait, intention and coping style are associated with adherence to a GFD.

Two new studies showed that self-efficacy was associated with better adherence. This may also be related to one study that showed that being prepared and organised was associated with better adherence. Additionally, a low quality study (N=278) (Sainsbury et al., 2011) showed that having the confidence to ask about contamination is associated with improved adherence. Trusting other people to prepare their food was associated with poorer adherence.

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Overall knowledge, attitudes and beliefs are usually associated with adherence. However, reading food labels is unlikely to be associated with adherence.

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Table 2.6 Knowledge, attitudes and beliefs (including results from Hall et

al.’s (2009) systematic review)

Authors Adherence factor Number of

participants in studies that show an association with adherence Number of participants in studies that did not show an association with adherence Assessment of quality

Hall et al., 2009 Understanding of gluten-free food

1/11 (n=154) Moderate/High Sainsbury et al.,

2011

Knowledge of gluten-free ingredients was associated with better adherence

n=278 Low

Hall et al., 2013 Improved awareness and understanding was linked with better adherence

n=287 Moderate

Hall et al., 2009 Understanding and use of food labelling

1/21 (n=87) 1/21 (n=234) Moderate/High Sainsbury et al.,

2011

Reading food labels was associated with better adherence

n=278 Low

Hall et al., 2009 Beliefs about harm from exposure to gluten

1/11 (n=154) Moderate/High Ford, 2012 Belief in the serious

consequences of non- adherence was associated with better adherence

n=288 Moderate

Hall et al., 2013 Worry about the long-term impact of gluten consumption was associated with better adherence

n=287 Moderate

Sainsbury et al., 2011

Worry about the long-term impact of gluten consumption

n=278 Low

Ford et al., 2012 Weaker belief in the cyclical nature of coeliac disease was associated with better adherence

n=288 Moderate

Edwards- George, 2009

Higher conscientiousness was associated with better adherence

n=154 High

Edwards- George, 2009

Higher values trait was associated with better adherence

n=154 High

Edwards- George, 2009

Higher order trait was associated with better adherence

n=154 High

Edwards- George, 2009

Higher self-discipline trait was associated with better adherence

n=154 High

Edwards- George, 2009

Higher deliberation trait was associated with better adherence

n=154 High

Sainsbury et al., 2013a

Intention to adhere was associated with better adherence

n=390 Moderate

Sainsbury et al., 2013a

Task oriented coping (problem solving) was associated with better adherence

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Sainsbury et al., 2013a

Emotion oriented coping (feeling anxious or blaming oneself) was associated with better adherence

n=390 Moderate

Ford, 2012 Higher self-efficacy was associated with better adherence

n=288 Moderate

Hall et al., 2013 Higher self-efficacy was associated with better adherence

n=287 Moderate

Sainsbury et al., 2011

Being prepared and organised was associated with better adherence

n=278 Low

Sainsbury et al., 2011

Confidence to ask questions about contamination was associated with better adherence

n=278 Low

Sainsbury et al., 2011

Having trust in others to prepare GFF was associated with poorer adherence

n=278 Low

Note:

1. Figures shown here indicate the number of studies included in the systematic review by Hall et al. (2009) in relation to a particular adherence factor. For example, for ‘Understanding of gluten-free food’ one study out of one (1/1) from the Hall et al. (2009) systematic review showed an association between understanding of gluten-free food and adherence to a gluten-free diet

Illness and symptom factors

Table 2.7 shows the results of the analysis for studies that report on illness and symptom factors in relation to adherence to a GFD.

I identified two new studies examining time since CD diagnosis in relation to adherence, however, neither of these studies found an association with adherence to a GFD. Hall et al. (2009) found one small study (N=76) (out of three) that reported an association between adherence to a GFD and time since CD diagnosis. Overall, it is likely that time since CD diagnosis is not associated with adherence.

Hall et al. (2009) reported that most studies in their systematic review found no association between age at diagnosis and adherence to a GFD. I

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identified three new studies with more disparate results. Two of these studies reported that diagnosis at an older age was associated with better adherence to a GFD. There are now three studies that found an association, and six that found no association between age at diagnosis and adherence. So overall there is no strong evidence that age at diagnosis is associated with adherence to a GFD.

Two studies in the review by Hall et al. (2009) found the presence of symptoms at diagnosis to be associated with adherence to a GFD and one study that did not find an association. I found three new studies relating to symptoms at diagnosis which showed no association with adherence to a GFD. Overall, symptoms at diagnosis is now a factor with inconsistent evidence to support it.

Diagnostic delay was reported to be associated with adherence in one study (n=300) that was included in the review by Hall et al. (2009). I did not identify any further studies for this factor.

Hall et al. (2009) identified inconsistent evidence regarding whether having CD symptoms was associated with adherence. I identified three further studies that were also inconsistent in their results. One of these three studies showed no association with the presence of symptoms at diagnosis (n=278). One study reported poorer adherence in individuals who had experienced symptoms in the past four weeks (n=154) and one study showed better

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adherence in individuals who experience severe symptoms if gluten is consumed (n=390). In total four studies identified an association between CD symptoms and adherence to a GFD and five studies did not find an association, therefore, the evidence is inconclusive.

The presence of additional food intolerances was found to be associated with better adherence in one study in Hall et al.’s (2009) systematic review. I identified one further study that also found this association (Edwards- George et al., 2009).

I identified one large (n=1018) high quality study that reported an association between body weight and adherence to a GFD. This study showed that having a normal body weight was associated with better adherence, whilst being overweight was associated with non-adherence.

Overall, the level of symptoms, whether they led to a diagnosis, the time the person has had a diagnosis for CD, and at what age they received the diagnosis were not associated with adherence. The association between diagnostic delay and adherence to a GFD was evident in one study in the systematic review by Hall et al. (2009). There are two small studies that suggest that having additional food intolerances may be associated with adherence. One study that suggests that a patient’s body weight is associated with adherence.

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Table 2.7 Illness and symptom factors (including results from Hall et al.’s

(2009) systematic review)

Authors Adherence factor Number of

participants in studies that show an association with adherence Number of participants in studies that did not show an association with adherence Assessment of quality Hall et al., 2009

Time since diagnosis 1/31 (n=76)2 2/31 (n=230)2 Moderate/High Barratt et al.,

2011

Time since diagnosis n573 Moderate

Hall et al., 2013

Time since diagnosis n=287 Moderate

Hall et al., 2009

Age at diagnosis 1/61 (n=29)2 5/61 (n=1284)2 Moderate/High Hall et al.,

2013

Age at diagnosis (those diagnosed as adults had better adherence)

n=287 Moderate

Hopman, 2009

Age at diagnosis (those diagnosed at an older age had better adherence)

n=53 Moderate

Hutchinson, 2010

Age at diagnosis n=284 High

Hall et al., 2009 Presence of symptoms at diagnosis 2/31 (n=454)2 1/3 (n=154)2 Moderate/High Barratt et al., 2011 Presence of symptoms at diagnosis n=573 Moderate

Paavola, 2012 Screen detected/ symptom detected

n=576 High

Kabbani, 2012 Type of symptoms present at diagnosis (gastrointestinal or extra-gastrointestinal)

n=679 High

Hall et al., 2009

Diagnostic delay 1/11 (n=300)2 Moderate/High Hall et al.

(2009)

Coeliac disease symptoms experienced

2/61 (n=590)2 4/61 (n=642)2 Moderate/High Edwards-

George (2009)

Symptoms experienced in the 4 weeks prior to the study was associated with poorer adherence

n=154 High

Sainsbury et al., 2011

Coeliac disease symptoms experienced

n=278 Low

Sainsbury et al., 2013a

Higher severity of symptoms was associated with better adherence

n=390 Moderate

Hall et al., 2009

Presence of additional food intolerances was associated with better adherence

1/11 (n=154)2 Moderate/High Edwards

George et al.., 2009

Presence of additional food intolerances was associated with better adherence

n=154 High

Kabbani, 2012 Body weight (obesity higher in non-adherent group; normal BMI is higher in adherent group)

n=1018 High

Note:

1. The figures shown here indicate the number of studies included in the systematic review by Hall et

al. (2009) in relation to a particular adherence factor. For example, for ‘Time since diagnosis’ one out

of three (1/3) studies from the Hall et al. (2009) systematic review showed an association between time since diagnosis and adherence to a gluten-free diet and two out of three (2/3) showed no association between adherence and time since diagnosis.

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Healthcare treatment factors

Table 2.8 shows the results of the analysis for studies that report on healthcare treatment factors in relation to adherence to a GFD. Hall et al. (2009) identified five studies that showed disparate results regarding the duration of following a GFD with adherence. Although there were four studies showing no association, the total number of participants in these studies (n=385) was not substantially larger than the one study that showed an association (n=200). I identified no further studies for this factor.

I identified two new studies that showed that people who believe that following a GFD is difficult was associated with adherence, however, the results of these two studies were conflicting. One study (n=2922) found poorer adherence in those who believed the GFD was difficult to follow, whereas the other study (n=278) found poorer adherence in individuals who believe it is not difficult to eat a nutritionally balanced GFD. Hall et al. (2009) found one small (n=73) study that showed no association between adherence and perception of difficulty in following the GFD. Although my two new studies were large (total N= 3200) their quality was low and the conflicting findings lead me to conclude that there appears to be no association between perceived difficulty in following a GFD being associated with adherence.

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Receiving GFF on prescription was a new factor that one moderate quality study by Hall et al. (2013) identified as being associated with better adherence to a GFD (N=287).

In their systematic review, Hall et al. (2009) found inconsistent support for satisfaction with information from a healthcare provider being associated with adherence. I found no new studies in relation to this factor.

I identified one new study that showed no association between attendance at a coeliac clinic and adherence to a GFD (n=413). This finding is in contrast to Hall et al. (2009) who found one study that showed an association between attendance at a coeliac clinic and adherence to a GFD (n=99). Overall there is inconsistent support to show that this factor is associated with adherence to a GFD.

The regularity of follow-up was shown by Hall et al. (2009) to have inconsistent support for its association with adherence. I identified one more study that showed an association with adherence, and overall the balance of evidence does appear to be tending towards there being an association. In total, three studies (total N=764) reported an association between adherence and the regularity of follow-up and one study (N=207) did not find an association.

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I identified one more study that showed that membership of a coeliac support group is associated with better adherence, which is in concordance with the two studies reported in the systematic review by Hall et al. (2009).

Overall I have identified inconsistent support for duration of GFD, difficulty

In document Gluten-free diet adherence in adult coeliac disease: Exploring multiple perspectives (Page 90-115)