METHODS

Three hundred and three postmenopausal women, admitted to the Osteoporosis Unit of the Physical Medicine and Rehabilitation Department of Trakya University were included in the study. The study was approved by the Ethical Committee of the Trakya University Medical Faculty. The detailed demographic history of all patients was recorded. A structured interview was used to obtain information on reproductive histories of all the patients. BMD values, duration of breast-feeding, age at menarche, age at first pregnancy, number of pregnancies and number of abortions were recorded (Table 1). The sample consisted of patients who experienced menopause over the age of 40, and patients with early or secondary menopause were excluded from the sample. The postmenopausal patients were divided into four groups on the basis of the number of pregnancies; nullipare (n= 24), one or two parities (n= 136), three or four parities (n= 106), and five or more parities (n= 37)(Table 2). The patients were also grouped on the basis of number of abortions; no abortion (n= 124), one or two abortions (n= 122), three or four abortions (n= 43) and five or more abortions (n= 14). Total duration of breast feeding of the patients was recorded in months. Measurements of bone mass were performed by dual-energy X-ray absorptiometry (DEXA),(Norland XR 36, Norland Medical Systems Inc., Fort Atkinson, WI USA) at the lumbar spine, femoral neck, trochanter and Ward’s triangle (an area just distal to the intersection of these two sets of trabeculae in the femoral neck). Statistical analysis was performed using SPSS 10.0 software. The demographic findings were reported in terms of the mean and the standard deviation values. Between groups comparisons were conducted using presence of increased risk of osteoporosis in women (Kritz-Silverstein and Barrett-Connor 1993). Several determinants such as genetic predisposition, some reproductive factors and life style may, as well, play a role in the development of primary osteoporosis. Some of the reproductive factors that may have an effect on peak bone mass and bone loss, are age at menarche, age at first pregnancy, number of pregnancies and duration of breast feeding. Previous studies have shown a positive correlation between age at menopause and BMD, and a negative correlation between age at menarche and BMD (Kritz-Silverstein and Barrett-Connor 1993; Forsmo et al. 2001). Menarche may be having a stimulating effect on the development of bone by increasing the osteoblastic activity via accompanying the unsettled estrogen (Jaffe and Dell’Acqua 1985; Ito et al. 1995). The underlying mechanism regarding the effects of age at menarche on bone development and the density has not been completely explained, yet. However, a number of studies have been carried out investigating the relation between BMD and age at menopause and the length of the reproductive period (Osei-Hyiaman et al. 1998).

Findings about the relation between parity and BMD are controversial (Gur et al. 2003). Evidence shows that pregnancy at an earlier age, as both the mother’s and the fetus’s skeletons are concurrently maturing, may result in lower bone density and increased risk for perimenopausal bone loss (Sowers 2001). Breast-feeding may pause a significant stress on calcium metabolism and, consequently, have an impact on the bone metabolism. The duration and frequency of breast feeding are of the most significant factors affecting BMD and bone metabolism. Long-term breast feeding is associated with increased bone loss (Melton et al. 1993; DeSantiago et al. 1999; Glerean and Plantalech 2000; Popivanov and …