Spurious associations in oral epidemiological research: the case of dental flossing and obesity

Abstracts on this page have been chosen and edited by Dr Trevor Watts

Abstract

An association between flossing behaviour and body mass index (BMI) illustrates that behavioural factors are a major confounder in studies alleging causal relationships between dental disease and systemic diseases.

Main

Hujoel PP, Cunha-Cruz J et al. J Clin Periodontol 2006; 33: 520–523

In some periodicals, people have been advised to floss more so as to lose weight. If single factors are isolated from the complexity of an individual's health-related behaviour, there may be serious misinterpretation of associations. Smoking usually cannot be fully taken into account, and therefore studies are advised in never-smokers. However, there may be other significant confounders. In this study, 1,497 subjects attending a periodontal specialist were asked to complete a questionnaire on flossing and various health parameters.

Respective significant odds ratios for lack of flossing and being overweight (BMI: 25-30), obese (30-40) or morbidly obese (40+), were 1.5, 2.0 and 22.5 when adjusted only for age and gender, similar when also adjusted for diabetes, smoking and periodontal condition, and in never smokers (none morbidly obese) were 2.3 and 2.7. The authors discuss the unlikelihood of a causal relationship, and account for the association in terms of overall health behaviour.