Age
Biro, F. M., Greenspan, L. C., Galvez, M. P., Pinney, S. M., Teitelbaum, S., Windham, G. C., ... & Kushi, L. H. (2013). Onset of breast development in a longitudinal cohort. Pediatrics, 132(6), 1019-1027.
Research question: Does age of the onset of breast development (Thelarche) vary by race/ethnicity and BMI?
Study sample: 1200 girls 6 to 8 years of age living in San Francisco Bay Area, Cincinnati, and New York City from the Breast Cancer and the Environment Research Program (BCERP).
Longitudinal design: Semi-annual or annual visits from date of enrollment (between 2004 and 2008) through March 2012. Mean follow-up was 4.3 years.
Analysis: Kaplan-Meier analyses were used to describe age at onset of breast maturation
Time since enrollment
Browner, W. S., Pressman, A. R., Nevitt, M. C., & Cummings, S. R. (1996). Mortality following fractures in older women: the study of osteoporotic fractures. Archives of internal medicine, 156(14), 1521-1525.
Research question(s): Does mortality increase after fractures?
Study sample: Women 65 years of age or older who had bilateral hip replacement in the Study of Osteoporotic Fractures (SOF).
Longitudinal design: Baseline measurements were taken and participants or their proxy returned a postcard every 4 months reporting the occurrence of fractures. Death certificates and hospital discharge summaries were reviewed for women who died in order to determine if any fractures had occurred since the last follow-up.
Analysis: Multivariable proportional hazards models were used to determine association between fractures and age-adjusted mortality.
Time since diagnosis
Tzeng, H. E., Muo, C. H., Chen, H. T., Hwang, W. L., Hsu, H. C., & Tsai, C. H. (2015). Tamoxifen use reduces the risk of osteoporotic fractures in women with breast cancer in Asia: a nationwide population-based cohort study. BMC musculoskeletal disorders, 16(1), 123.
Research question: Is Tamoxifen use associated with Osteoporotic fractures?
Study sample: 75488 women with breast cancer with no prior history of fractures from the Longitudinal Health Insurance Database for Catastrophic Illness Patients in 2000-2011.
Longitudinal design: Women were followed from date of diagnosis of breast cancer (index date) to the date a hip, vertebrate or wrist fracture occurred.
Analysis: Cox proportional hazards model with time-dependent covariates to estimate risk of a fracture.