Does stage of change modify the effectiveness of an educational intervention to improve diet among family members of hospitalized cardiovascular disease patients?

Abstract

Objective: The purpose of this study was to evaluate whether effectiveness of a special intervention to improve diet vs a control intervention differs by readiness to reduce dietary saturated fat based on the Transtheoretical Model Stages of Change among family members of hospitalized cardiovascular disease patients.

Design: Stages of change (ie, precontemplation, contemplation, preparation, action, maintenance) were assessed by standardized questionnaire. Diet was measured by Block 98 Food Frequency Questionnaire at baseline and 1 year in participants in the Family Intervention Trial for Heart Health (n=501; 36% racial/ethnic minorities; 66% female). Therapeutic Lifestyle Change diet education was provided to each special intervention subject tailored to baseline stage of change.

Statistical analyses: Multivariable linear regression was used to examine whether the effect of the intervention was modified by stage of change.

Results: Baseline saturated fat and cholesterol intakes were lower among those in maintenance stage vs others (9.9% vs 11.2% kcal; P<0.0001 and 112.2 vs 129.7 mg/1,000 kcal; P=0.0003, respectively). Overall, change in the percentage of calories from saturated fat from baseline to 1 year was -0.7 in the special intervention vs -0.4 in the control intervention (P=0.18). Among participants in contemplation, greater reductions in saturated fat (-2.1% vs +0.3% kcal; P=0.04) and cholesterol (-34.0 vs +32.6 mg/1,000 kcal; P=0.01) were seen in the special intervention vs control intervention. The special intervention was more likely than control intervention to achieve new adherence to a diet of <10% saturated fat/<300 mg cholesterol at 1 year among those not in maintenance stage (30% vs 15%; P=0.03). Control intervention participants were more likely than special intervention to revert to lower levels on the stage of change continuum from baseline to 1 year (17% vs 7%; P=0.002).

Conclusion: Effectiveness of an intervention to lower saturated fat varies by baseline stage of change among family members of hospitalized cardiovascular patients. This can be important to consider when designing research or clinical diet interventions.