The Evolution of the WHI 80+ Cohort.

BACKGROUND

The Women's Health Initiative has collected data on the aging process of postmenopausal women for over two decades, including data on many women who have achieved age 80 years and older. However, there has not been any previous effort to characterize the 80+ cohort and to identify associated retention factors.

METHODS

We include all women at baseline of the Women's Health Initiative who would be at least 80 years of age as of September 17, 2012. We summarize retention rates during the study and across two re-enrollment campaigns as well as the demographic and health-related characteristics that predicted retention. Further, we describe the longitudinal change from baseline in the women identified as members of the 80+ cohort.

RESULTS

Retention rates were lower during each of two re-enrollment periods (74% and 83% retained during re-enrollment periods 1 and 2, respectively) than during the first and second data collection periods (90% each). Women who were retained were more likely to be white, educated, and healthier at baseline. Women age 80 and older saw modest changes in body mass index and depression burden, despite lower physical activity and increased cardiovascular disease.

CONCLUSIONS

The characteristics of women who were retained in the 80+ cohort differ in significant ways compared with their peers at baseline. Identifying the characteristics associated with attrition in older cohorts is important because aging and worsening health has a negative impact on study attrition. Strategies should be implemented to improve retention rates among less healthy older adults.