Noncompliance in lifestyle intervention studies: the instrumental variable method provides insight into the bias.

Objective: In lifestyle intervention trials, participants of the control group often change their behavior despite the request to maintain their usual lifestyle pattern. These changes in the control group and changes in addition to the intended in the intervention group can lead to undesirable confounding effects.

Study Design And Setting: We address several considerations for study design to prevent noncompliance or minimize its effects.

Behavioral changes after a 1-yr exercise program and predictors of maintenance.

Purpose: Public health strategies attempt to stimulate participation in physical activity, aiming at permanent behavior change. We assessed the sustained effect of participating in an exercise program on physical activity behavior 1 yr after completion of the program. Furthermore, we aimed to identify factors that predict sustained exercise participation.

Sudden death in persons younger than 40 years of age: incidence and causes.

Background: The problem of sudden death in the young is currently debated and measures for prevention are being evaluated worldwide. Information on the incidence and causes of sudden (cardiac) death in the young (1-40 years) is essential for the development of these preventive strategies.

Methods: Incidence estimates and causes of death were determined using death certificate data of out-of-hospital sudden deaths recorded by Statistics Netherlands from 1996 to 2006.

Validity of the modified Baecke questionnaire: comparison with energy expenditure according to the doubly labeled water method.

Background: In epidemiological research, physical activity is usually assessed by questionnaires. Questionnaires are suitable for large study populations since they are relatively inexpensive and not very time consuming. However, questionnaire information is by definition subjective and prone to recall bias, especially among elderly subjects.