The influence of duration of breastfeeding on bone mass in postmenopausal women of different age groups.

This study examines the influence of duration of breastfeeding on bone mineral density (BMD) and investigates the relationship between duration of breastfeeding and bone mass at four sites in postmenopausal women of different ages. A total of 509 postmenopausal women aged 45-86 years were included in the study. Patients were divided into three groups: never breastfed (n=67), < 96 months (n=157) and > or = 96 months (n=285); they were further classified into two age groups, 40-59 years (n=233) and 60-80 years (n=276). In all patients and in the 40-59 year age group, BMD of the spine was found to be significantly lower in the never-breastfed group, while BMD of the trochanter was significantly lower in the > or = 96 month breastfeeding group. BMD of the spine and femur tended to decrease with longer breastfeeding in all groups, while BMD of the spine and trochanter tended to decrease with longer breastfeeding in the 40-59 year group. Of patients in the 60-80 year group who had never breastfed, spinal BMD was significantly higher than that of the > or = 96 month group, while in the > or = 96 month group trochanter BMD was significantly lower than in other groups. In the never-breastfed group, ward's triangle BMD was significantly higher than that of other groups. There was a significant correlation between duration of breastfeeding and BMD of the spine, neck, trochanter and ward's triangle. The study suggests that duration of breastfeeding has an effect on BMD, and extended breastfeeding leads to lower BMD.