Psychometric properties of brief indexes designed to measure social-cognitive predictors of smoking initiation.

BACKGROUND: Constructing indexes which measure factors that may predict smoking initiation is essential for planning prevention programs. Our aim was to examine the criterion-related construct validity of brief psychological indexes of attitude, social influence and self-efficacy to be used in future studies for predicting smoking initiation in adolescents. METHODS: Five indexes were evaluated using cross-sectional data on 4819 adolescents age 13 in a random sample of schools in six Danish counties. Item analyses were performed with the graphical log-linear Rasch model, a modification of the Rasch model that allows for differential item functioning and positive local dependence. RESULTS: The three indexes social influence-norms, social influence-pressure and attitude showed acceptable deviations from the Rasch model, while the two indexes self-efficacy and social influence-behavior were invalidated by negative local dependence. CONCLUSION: Of the five tested indexes, three (social influence-norms, social influence-pressure and attitude) showed acceptable criterion-related construct validity and may be considered unbiased representations of the theory-based factors if statistical analyses are appropriately adjusted. The results of this population-based study show that the graphical log-linear Rasch model is useful for evaluating health-related behavior indexes and identifying problems, which can be dealt with when using the indexes in future studies.

Personality traits, health behavior, and risk for cancer: a prospective study of Swedish twin court.

BACKGROUND: The authors conducted a prospective investigation into the relation between personality traits and the risk for cancer. METHODS: The study cohort consisted of 29,595 Swedish twins from the national Swedish Twin Registry who were ages 15-48 years at time of entry. In 1973, the twins completed a questionnaire eliciting information on personality traits and health behavior. The Eysenck Personality Inventory was used to measure neuroticism and extroversion as two personality dimensions. A Cox proportional hazards model was used to estimate hazard ratios and 95% confidence intervals for extroversion and neuroticism separately as well as for their joint effect, and conditional logistic regression analyses were conducted to estimate the relation between personality traits and risks for cancer in twin pairs who were discordant for cancer. All analyses were conducted for six etiologically different groups of cancers: hormone-related organ cancers, virus-related and immune-related cancers, digestive organ cancers (excluding liver), respiratory organ cancers, cancers in other sites, and all cancer sites. RESULTS: Follow-up in the Swedish Cancer Registry for 1974-1999 revealed 1898 incidents of primary cancer. The authors found no significant association between neuroticism, extroversion, their joint effects and the risk for any cancer group. CONCLUSIONS: The current results did not support the hypothesis that certain personality traits are associated with cancer risk.