Mis-reporting, previous health status and health status of family may seriously bias the association between food patterns and disease

Abstract

Background: Food pattern analyses are popular tools in the study of associations between diet and health. However, there is a need for further evaluation of this methodology. The aim of the present cross-sectional study was to evaluate the relationship between food pattern groups (FPG) and existing health, and to identify factors influencing this relationship.

Methods: The inhabitants of Västerbotten County in northern Sweden are invited to health check-ups when they turn 30, 40, 50, and 60 years of age. The present study includes data collected from almost 60,000 individuals between 1992 and 2005. Associations between FPG (established using K-means cluster analyses) and health were analyzed separately in men and women.

Results: The health status of the participants and their close family and reporting accuracy differed significantly between men and women and among FPG. Crude regression analyses, with the high fat FPG as reference, showed increased risks for several health outcomes for all other FPGs in both sexes. However, when limiting analysis to individuals without previous ill-health and with adequate energy intake reports, most of the risks instead showed a trend towards protective effects.

Conclusions: Food pattern classifications reflect both eating habits and other own and family health related factors, a finding important to remember and to adjust for before singling out the diet as a primary cause for present and future health problems. Appropriate exclusions are suggested to avoid biases and attenuated associations in nutrition epidemiology.

Figure 1

Relation between food patterns groups (FPGs) among women and risk of being diagnosed with IFG/IGT/diabetes. Multivariate regression analysis of relation between food patterns groups (FPGs) and risk of being diagnosed with IFG/IGT/diabetes at the health check-up among women in the whole population (crude - top), and among only the Previously Healthy Adequate Reporters (crude - middle and adjusted - bottom), in northern Sweden, 1992-2005. (OR and 95% CI). "High fat" FPG used as reference group. Abbreviations: BMI = body mass index, kg/m²; CI = confidence interval; IFG = impaired fasting glucose; IGT = impaired glucose tolerance; OR = odds ratio; Significantly increased risk marked with red (solid line) and significantly decreased risk with green (dashed line). ¹Adjusted for previously being told about high blood pressure (but not taking medication), family history of ill health, age, BMI, education, cohabiting status, living area, physical leisure activity, smoking, snuff use, alcohol use.