Derivation and external validation of a risk score for clinically important declines in health and function among two longitudinal cohorts of women in the mid-life

OBJECTIVES: Women in mid-life often develop chronic conditions and experience declines in physical health and function. Identifying factors associated with declines provides opportunity for targeted interventions. We derived and externally validated a risk score for clinically important declines over 10 years among women ages 55-65 using the Physical Component Summary Score (PCS) of the SF-36. DESIGN: Derivation and validation of a risk score. SETTING: Two longitudinal cohorts from sites in the USA were used. PARTICIPANTS: Women from the Study of Women's Health Across the Nation (SWAN) and women from the Women's Health Initiative (WHI) Observational Study and/or clinical trials. OUTCOME MEASURES: A clinically important decline over 10 years among women ages 55-65 using the PCS of the SF-36 predictors was measured at the beginning of the 10 years of follow-up. RESULTS: Seven factors-lower educational attainment, smoking, higher body mass index, history of cardiovascular disease, history of osteoarthritis, depressive symptoms and baseline PCS level-were found to be significant predictors of PCS decline among women in SWAN with an area under the curve (AUC)=0.71 and a Brier Score=0.14. The same factors were associated with a decline in PCS in WHI with an AUC=0.64 and a Brier Score=0.18. Regression coefficients from the SWAN analysis were used to estimate risk scores for PCS decline in both cohorts. Using a threshold of a 30% probability of a significant decline, the risk score created a binary test with a specificity between 89%-93% and an accuracy of 73%-79%. CONCLUSIONS: Seven clinical variables were used to create a valid risk score for PCS declines that was replicated in an external cohort. The risk score provides a method for identifying women at high risk for a significant mid-life PCS decline.