Interactions between time trends in dietary behaviors and the socio-economic environment, and cancer risk in the E3N cohort study

  • Topic: Combination of Cancers
  • Institution: Centre for Research in Epidemiology and Population Health
  • Country: France
  • Status: Ongoing

Scientific abstract

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Background

Associations between dietary habits and cancer have been extensively investigated. However, while some associations between dietary factors and cancer risk are classified between “certain” to “lack of evidence” by World Cancer Research Fund International’s CUP meta-analyses, there is still too little strong evidence for consistent associations. In parallel, there is an increasing interest for food patterns in nutritional epidemiology. The two most frequent reported a posteriori dietary patterns are the “Western” and the “Prudent” patterns, which have respectively been positively and inversely associated with cancer risk. Most studies so far have focused on specific cancer sites and only few studies have longitudinal data that enable to study the influence of dietary changes on the risk of developing cancer risk or after a cancer diagnosis. Finally, in terms of methodology, most studies derived dietary patterns from principal component and factor analyses, which provide non mutually exclusive patterns. On the other hand, the socio-economic status has been recognised to influence dietary behaviours, but also to be associated with heterogeneity in cancer risk. Thus studying the interaction of the socio-economic environment with the evolution of dietary habits over time on risk of incident cancer or after a cancer diagnosis, is of major interest.

Hypothesis and objectives

Our two main hypotheses are:

  1. Changes in dietary patterns affect cancer risk, and are influenced by socio-economic factors.
  2. Cancer occurrence may affect dietary behaviours, and differentially according to the socio-economic status.

Therefore, based on data from the large prospective E3N cohort study, our objectives are:

  1. To study dietary habits evolution over time (12 years) according to the socio-economic status.
  2. To test the interactions between dietary habits evolution and the socio-economic environment on the risk of developing cancer.
  3. To test the differences of dietary evolutions between women who had a cancer diagnosis and cancer-free women according to the socio-economic environment.

Settings and methods

The E3N cohort study has been prospectively recording data on exposure and disease outcomes in ca.100 000 women since 1990. Women filled in two detailed meal-based food frequency questionnaires in 1993 and 2005 (N=58 385). We will investigate changes in dietary behaviours between 1993 and 2005 according to available information on the socio-economic status (eg. education, residence, etc.). Dietary patterns will be identified both by classical methods and by innovative statistical methods such as latent class and transition analyses for building up mutually exclusive patterns. We will first study twelve-year changes in dietary behaviours in relation with subsequent cancer risk according to the socio-economic status. We will then compare changes in dietary patterns between women who had a cancer diagnosed between the two diet questionnaires and cancer-free women, according to the socio-economic status. Hazard ratios (HRs) for cancer and 95% confidence intervals (CIs) will be calculated using Cox proportional hazards regression models.

Impact

This project is a unique opportunity to identify optimal dietary behaviours to minimise cancer risk, taking into account the socio-economic background, as well as to identify major changes in dietary behaviours after cancer diagnosis, in order to adjust primary and secondary prevention advice.

Plain language abstract

Background

The relationship between dietary habits and cancer are not totally well-understood and there is a need of additional large prospective studies to address this issue so that dietary recommendations such as those provided by World Cancer Research Fund (WCRF) can be updated. Historically, nutrition has mainly been studied in terms of specific food or food groups but recently, more and more studies have considered nutrition overall, in terms of dietary patterns. Two patterns are largely characterised in the literature: the “Western pattern”, characterised by a high consumption of processed foods, sweetened beverages, and meat, and the “Prudent pattern”, characterised by a high consumption of fruits, vegetables, fish, etc. It is established that people having a strong adherence to the western pattern are more at risk of cancer, unlike to those following the prudent pattern. In most studies, specific cancer sites have been studied. There is a need of an overview of the associations between dietary patterns and both overall cancer risk and by most frequent sites. Furthermore existing studies have some limitations. First, only a few studies have a food data collection repeated over time that enables the study of changes in dietary behaviours over time and its influence on cancer risk and/or dietary changes after cancer diagnosis. In addition, the traditional statistics used to derive food patterns have some limitations. So we suggest the use of innovative methodology. Moreover, we expect that the socio-economic status will influence both the evolution of the dietary behaviours over time and cancer risk, so we will systematically evaluate the “diet-cancer” relationship in different strata defined by key socio-economic indexes.

Aims and objectives

Based on data from the large prospective E3N cohort study, we will perform three types of analysis: 1) we will study dietary habits evolution over time (12 years) according to socio-economic status; 2) we will study how changes in dietary patterns affect cancer risk, in different sub-populations defined by socio-economic factors; 3) we will study how cancer occurrence affects dietary behaviours evolution, and differentially according to the socio-economic status.

How it will be done

The E3N cohort study has been prospectively recording data on exposure and disease outcomes in 100,000 women since 1990. About 60,000 of them have filled in two detailed meal-based food frequency questionnaires in 1993 and 2005. We will then investigate changes in dietary behaviours between 1993 and 2005 according to available information on the socio-economic status (e.g. education, residence, etc.). Dietary patterns will be identified by innovative statistical methods (LCA, LTA) for building up mutually exclusive patterns. We will first study twelve-year changes in dietary behaviours in relation with subsequent cancer risk according to the socio-economic status. We will also compare changes in dietary patterns between women who had a cancer diagnosed between the two diet questionnaires and cancer-free women, according to the socio-economic status.

Potential impact

This project is a unique opportunity to identify optimal dietary behaviours to minimise cancer risk, taking into account the socio-economic background, as well as to identify major changes in dietary behaviours after cancer diagnosis, in order to adjust prevention advice.