Predictors of adherence in the Women's Health Initiative Calcium and Vitamin D Trial

UMMS Affiliation

Department of Medicine, Division of Preventive and Behavioral Medicine

Publication Date


Document Type



Aged; Attitude to Health; Calcium, Dietary; *Dietary Supplements; Double-Blind Method; Female; Forecasting; Humans; Longitudinal Studies; Medication Adherence; Middle Aged; Postmenopause; Risk Factors; Vitamin D; *Women's Health


Life Sciences | Medicine and Health Sciences | Women's Studies


The authors analyzed data from the Women's Health Initiative (WHI) Calcium and Vitamin D Supplementation Trial (CaD) to learn more about factors affecting adherence to clinical trial study pills (both active and placebo). Most participants (36,282 postmenopausal women aged 50-79 years) enrolled in CaD 1 year after joining either a hormone trial or the dietary modification trial of WHI. The WHI researchers measured adherence to study pills by weighing the amount of remaining pills at an annual study visit; adherence was primarily defined as taking > or = 80% of the pills. The authors in this study examined a number of behavioral, demographic, procedural, and treatment variables for association with study pill adherence. They found that relatively simple procedures (ie, phone contact early in the study [4 weeks post randomization] and direct social contact) later in the trial may improve adherence. Also, at baseline, past pill-use experiences, personal supplement use, and relevant symptoms may be predictive of adherence in a supplement trial.

DOI of Published Version



Behav Med. 2009 Winter;34(4):145-55. Link to article on publisher's site

Journal/Book/Conference Title

Behavioral medicine (Washington, D.C.)

Related Resources

Link to Article in PubMed

PubMed ID