Osteoporosis is a condition that affects the structure of bones as we age. Healthy young bone is rather like the inside of a Crunchie bar – a dense network of solid material around lots of tiny holes. As we age, the holes get bigger and the solid material shrinks – more like an Aero! Eventually, the density falls so low that bones become weak and liable to fracture easily: this is osteoporosis. The size and shape of bone also contributes to risk of fracture.
People who have large, dense bones in middle-age can weather age-related bone loss without reaching the critically low levels that define osteoporosis. The challenge we face is to ensure that as many people as possible reach middle age with such healthy bones.
Research into osteoporosis needs state-of-the-art images of bone that show its size, shape and structure in great detail – and these images need to be repeated to examine changes over time. With this in mind, many of the HCS participants have had their bones studied in great detail using a range of techniques such as x-rays, DXA, pQCT and high resolution pQCT scanning (see the ‘Key Findings’ section on ‘Bone Imaging Techniques’ for more detail).
Work in Hertfordshire has demonstrated that influences acting before birth and in infancy affect later bone health:
- Men and women who were bigger at birth and at one year of age had bigger, denser bones in later life (1, 2).
- Infant growth affects the shape of bones as well; smaller babies grew up to have more vulnerable hip joints than bigger babies, due to differences in the shape of their leg-bone (3).
- pQCT scans can estimate the amount of stress a bone could withstand before breaking. We used these scans to show that people who were bigger at birth and at age one had stronger bones (4).
- Using DNA from blood tests, we showed that genetic differences in the way we handle Vitamin D affect bone density more in babies who are small at birth than in bigger ones (5). This is important because people who have low levels of Vitamin D are more likely to fracture than those whose levels are high.
This suggests that in order to improve bone health in future generations of older people, we need to act while they’re young – or even before they’re born. We are carrying out trials in pregnant women to see if taking vitamin D supplements strengthens their babies’ bones. If it does, we expect supplementation to become a standard part of maternity care.
- Dennison EM, Syddall HE, Sayer AA, Gilbody HJ, Cooper C. Birth Weight and Weight at 1 Year Are Independent Determinants of Bone Mass in the Seventh Decade: The Hertfordshire Cohort Study. PediatrRes. 2005;57:582-6.
- Cooper C, Javaid MK, Taylor P, Walker-Bone K, Dennison E, Arden N. The fetal origins of osteoporotic fracture. Calcif Tissue Int. 2002;70:391-4.
- Javaid MK, Lekamwasam S, Clark J, Dennison EM, Syddall HE, Loveridge N, et al. Infant growth influences proximal femoral geometry in adulthood. J Bone MinerRes. 2006;21:508-12.
- Oliver H, Jameson KA, Sayer AA, Cooper C, Dennison EM. Growth in early life predicts bone strength in late adulthood: The Hertfordshire Cohort Study. Bone. 2007;41(3):400-5.
- Dennison EM, Arden NK, Keen RW, Syddall H, Day IN, Spector TD, et al. Birthweight, vitamin D receptor genotype and the programming of osteoporosis. Paediatr Perinat Epidemiol. 2001;15:211-9.