A cross-sectional analysis demonstrated the healthy volunteer effect in smokers

J Clin Epidemiol. 2005 Apr;58(4):378-82. doi: 10.1016/j.jclinepi.2004.10.013.


Objective: This cross-sectional descriptive analysis sought to determine if a healthy volunteer effect can be demonstrated among smokers selected to participate in a dietary intervention trial.

Study design and setting: Body mass index (BMI), body fat, physical activity, dietary intake, and plasma concentration of antioxidant nutrients and carotenoids were assessed cross-sectionally, at the time of enrollment into a dietary intervention trial, among 136 adult smokers.

Results: Mean BMI was below national age- and gender-specific averages as was prevalence of overweight and obesity. Physical activity was reported to average 15.4 h/wk. Compared with other sample populations of smokers, our smokers reported lower total fat and cholesterol intakes, higher vitamin C and beta-carotene intakes, and generally equal vitamin E intakes. Plasma ascorbic acid, alpha-tocopherol, alpha- and beta-carotene, and beta-cryptoxanthin concentrations were higher than those of smokers surveyed by NHANES III.

Conclusion: These findings suggest that a "healthy volunteer effect" can be described among adult smokers. Future dietary intervention trials among smokers should cautiously estimate sample size because smokers electing to participate may report healthier dietary patterns than other smokers. Screening criteria regarding baseline micronutrient status of smokers should be evaluated given that intervention effects may be dependent on overall health status.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Antioxidants / analysis*
  • Ascorbic Acid / administration & dosage
  • Ascorbic Acid / blood
  • Bias
  • Body Mass Index
  • Carotenoids / blood
  • Diet
  • Dietary Fats / administration & dosage
  • Female
  • Health Status
  • Humans
  • Male
  • Micronutrients / blood
  • Middle Aged
  • Smoking / blood*
  • Smoking / epidemiology
  • Vitamin E / administration & dosage
  • beta Carotene / administration & dosage


  • Antioxidants
  • Dietary Fats
  • Micronutrients
  • beta Carotene
  • Vitamin E
  • Carotenoids
  • Ascorbic Acid