OSTEOPOROSIS ( Low birth weight babies have a lower bone mass which persists throughout their lives )

The strength of a bone depends on its size and the density of the calcium salts within it. This ‘bone mass’ reaches a peak in early adult life and thereafter gradually declines. The risk of osteoporotic fractures, that occur in the hip, spine or forearm, therefore depends on the peak bone mass attained and the subsequent rate of loss. Low birth weight babies have a lower bone mass which persists throughout their lives. People who were small at birth or who did not thrive during infancy also have life-long alterations in two hormones, growth hormone and cortisol, which influence bone mass. These alterations lead both to lower peak bone mass and to more rapid loss of bone mass with age.

The risk of an osteoporotic fracture is higher in older people who are frail. Slow growth in the womb and during the first few months after birth is accompanied by a reduction in the amount of muscle that is laid down. This is a lifelong problem because little new muscle is made after that age, and therefore people who had low birthweight tend to have low muscle mass through their lives. In old age their weakness can be measured by the reduced strength of their hand grip; and by their being readily fatigued by simple repetitive movements. They are less fit, a term which includes the body’s strength, flexibility and endurance. Within a group of people, the least fit have at least twice the death rates at each age compared to the most fit.