CD patients suffer from more symptoms and consume more health care before diagnosis and initiated gluten-free diet than they do afterwards. However, we did not observe a difference in the risk of developing other immune-mediated diseases after initiated treatment with a gluten-free diet.
This study is one of the largest of its kind and it has a high response rate. Its unique contribution is that it compares the situation before and after initiation of a gluten-free diet, including symptoms and health care consumption, which adds valuable information about individual and societal costs of untreated CD.
Our retrospective approach involves the risk of recall bias. We observed a similar pattern for symptom relief, health care visits, and missed working days when restricting our analysis to screened and recently diagnosed (2005–2009) CD patients. There was not a significant reduction in hospitalization days for the recently diagnosed (2005–2009) CD patients. This could indicate an improved situation due to earlier diagnosis, which we have reported earlier in the same population , or it might be due to problems remembering hospitalization days if diagnosed earlier than 2005. In an attempt to assess if the risk of developing associated immune-mediated diseases is affected by a gluten-free diet, we assumed that if fewer were diagnosed with the related disease after the CD diagnosis this would indicate a protective effect. The patient is likely to remember which disease was diagnosed first, but if there is a delay in diagnosis for one of the diseases the association could still be incorrect. A causal relation cannot be determined with certainty by a cross-sectional questionnaire study. An examination of hospital files would have been a valuable addition in this respect, but that was not within the scope of this study.
Retrospectively reported symptoms prior to a CD diagnosis have been studied previously , as have symptoms at the time of CD diagnosis [22–25]. Most studies have reported symptoms at the time of diagnosis that were obtained from medical records, making comparisons with our results difficult. Our main interest was to detect experienced changes in symptoms after initiated treatment with a gluten-free diet. Previously, similar comparisons were done for a more limited number of symptoms by Murray and colleagues in the United States, showing a similar positive pattern for investigated symptoms after initiated treatment for CD . Also Ukkola with colleagues showed an improvement in symptoms after initiated treatment with a gluten-free diet for Finnish CD patients . Little is known about the added costs of CD for individuals and society. Although many participants had their CD for a long time, and therefore were considerably older today, their health consumption was significantly lower today than prior to the CD diagnosis, indicating a decreased need for health care after initiated treatment with a gluten-free diet.
There is a well-known association between CD and other immune-mediated diseases . A protective effect of a gluten-free diet was proposed more than a decade ago [16, 28], but later studies have shown conflicting results [15, 18]. In our study 25% of the individuals reported associated immune-mediated diseases. The prevalences of autoimmune thyroid disease and diabetes mellitus type 1 were similar to figures previously reported in a Swedish CD population study based on patient chart reviews . Our results could not verify or reject a risk reduction effect of a gluten-free diet on the development of any of the associated immune-mediated diseases that were studied. Further studies are needed to investigate this relationship.
In a previous publication based on the same study population and questionnaire, we reported that there is a long delay until CD diagnosis and that CD patients experience a poor health-related quality of life that is significantly improved after initiation of a gluten-free diet . Considering this and the results of the present study, there is a strong implication that greater effort must be made to diagnose CD earlier to decrease the burden of both poorer health-related quality of life and CD-related symptoms. This would also result in economic savings for society in terms of a reduction in health care consumption and missed working days.
Recent studies have indicated that the extent of symptoms that patients detected through a population-based CD screening might have may be similar to that of non-CD persons [29, 30]. The screening-detected cases in our study were mainly from risk groups. They reported the same positive effect of symptom relief after diagnosis and initiated treatment with a gluten-free diet as the CD patients who had their primary investigation due to symptoms.