Short summary

Chronic inflammatory diseases (CID) - including Crohn's disease and ulcerative colitis, rheumatoid arthritis, axial spondyloarthritis, psoriatic arthritis, psoriasis and multiple sclerosis are diseases of the immune system that have some shared genetic and environmental predisposing factors, but still little is known on the effects of lifestyle as a prognostic factor on disease risk. This observational study will contribute to preexisting research on lifestyle factors by identifying diet factors associated with risk of developing CID, using prospective register data.

Rationale

The peak of disease-onset of CIDs is in the adult phase of life. The diseases have high impact on the patients and their families life quality due to lack of causative treatment and on the society due to absence from work and health care economy due to lack of preventative measures.

There are many potential mechanisms whereby environment such as diet may affect the immune system either directly or indirectly via e.g. the activity and composition of the gut microbiome. For example, low intake of fibre (which could otherwise serve as nutrient for the microbes) may lead to the microbial metabolism of mucus and to decrease of the intestinal mucus layer. A high intake of red and processed meat (containing organic sulphur and sulphate additives) may render the mucus layer penetrable to e.g. bacteria by reducing the disulphide bonds in the mucus network. Thus, microbes may reach the epithelium and activate the immune system.

The primary purpose of this study is to investigate the impact of low fibre/ high red and processed meat intake on risk of CID in the "Diet, Health and Cancer" (DHC) cohort.

The hypothesis is that "the risk of CID will be significantly higher among those with a low fibre/high red and processed meat intake compared to those with a high fibre/low red and processed meat intake." Based on previous research on a shared etiology in CIDs we hypothesize that "the postulated causality between low fibre/high red and processed meat intake and risk of developing CID is applicable for each of the CID-diagnoses."

The study design is a cohort study with prospective register data follows up. We will use the Danish cohort "Diet, Health and Cancer" (DHC), and combine data from the DHC cohort with Danish national registers (the National Patient Registry (NPR), the Danish Civil Registration Register, and The Danish National Prescription Registry). For this study we will extract data from NPR from 1993 to March 2018. The outcome CID is defined as at least one of the following diseases; inflammatory bowel disease (IBD), psoriasis/psoriatic arthritis, rheumatoid arthritis/ankylosing arthritis, or multiple sclerosis, during the follow-up period. The exposure is defined as high fiber intake and high red and processed meat intake and were collected at enrolment of the DHC cohort using questionnaires and interviews. 

Description of the cohort

The DCH Study is an ongoing Danish cohort study designed to investigate the relation between diet, lifestyle and disease risk. The cohort consists of 57,053 persons, recruited between December 1993 and May 1997. All the subjects (50 to 64 years of age) gave detailed information on diet (food frequency questionnaire) and other lifestyle data together with biological samples. Blood samples, anthropometric measures and questionnaire data on diet and lifestyle were collected at study entry.

The study will use data from all of the 57,053 participants in the DHC study with no CID diagnosis at entry. The number of persons developing a CID (defined as at least one of the mentioned CIDs) during follow up (1993/1997 - 2018) and the number of persons not developing a CID will be investigated. 

Data and biological material

Questionnaire data on diet and other lifestyle data will be retrieved from the DHC study data. Register data on CID diagnoses, medication and treatment will be retrieved from the National Patient Registry (NPR) and The Danish National Prescription Registry, and follow-up information on death and immigration will be retrieved from the Danish Civil Registration Register.

Collaborating researchers and departments

University of Southern Denmark

• Professor Vibeke Andersen, PhD, MD

Odense University Hospital, Odense Patient data Explorative Network (OPEN)

• Associate Professor Katrine Hass Rubin, PhD

Danish Cancer Society

• Professor Anne Tjønneland

Aarhus University

• Master student Nathalie Fogh Rasmussen

Publications associated with the project

Rubin KH, Rasmussen NF, Petersen I, Kopp TI, Stenager E, Magyari M, Hetland ML, Bygum A, Glintborg B, Andersen V. Intake of dietary fibre, red and processed meat and risk of late-onset Chronic Inflammatory Diseases: A prospective Danish study on the "diet, cancer and health" cohort. Int J Med Sci. 2020 Sep 9;17(16):2487-2495. doi: 10.7150/ijms.49314. PMID: 33029091; PMCID: PMC7532485.

Rubin KH, Rasmussen NF, Petersen I, et al. Intake of dietary fibre, red and processed meat and risk of late-onset Chronic Inflammatory Diseases: A prospective Danish study on the "diet, cancer and health" cohort. Int J Med Sci. 2020;17(16):2487-2495. Published 2020 Sep 9. doi:10.7150/ijms.49314

Rasmussen, N.F., Bech, B.H., Rubin, K.H. et al. Associations between participation in, intensity of, and time spent on leisure time physical activity and risk of inflammatory bowel disease among older adults (PA-IBD): a prospective cohort study. BMC Public Health 21, 634 (2021). https://doi.org/10.1186/s12889-021-10492-7