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Abstract
A longitudinal study was performed in a population based cohort of 173 men and 143 women aged 61-73 years, who had been born in Hertfordshire and who were still living there. These individuals were unique, because their birth records had been preserved. The principle objective of this study was to establish rates of bone loss at lumbar spine and proximal femur over a four year period, and to relate these loss rates to body build, adult lifestyle, hormonal status and growth in the first year of life. Baseline bone densitometry had been performed at both femoral neck and lumbar spine using a QDR 1000 instrument. Height and weight were recorded, and venous blood samples taken for measurement of parathyroid hormone, 25 hydroxyvitamin D, oestradiol, testosterone, SHBG and osteocalcin. Overnight urine samples were collected for measurement of Type I collagen cross linked N-telopeptide. Follow-up bone densitometry was performed four years later. Women lost bone at all sites; this ranged from 0.20%/year at the lumbar spine to 1.43%/year at the femoral trochanter. By contrast, men lost only 0.20%/year at the trochanteric region, and gained bone at the lumbar spine (0.33%/year) and at Wards triangle (0.27%/year) over the 4 year period. Lower baseline BMI and a greater rate of loss of adiposity over the follow-up period were both associated with significantly (p<0.05) greater bone loss. Other lifestyle factors protective against bone loss (after adjustment for BMI) included alcohol consumption at the femoral neck among women and physical activity at the lumbar spine among men. Gonadal steroids, calcitropic hormones and biochemical indices of bone turnover were not predictors of bone loss. Growth in infancy was correlated more strongly with skeletal size and mineral content at baseline than with bone loss rate.
