Bone Mineral Density and Hip Axis Length in Singapore’s Multiracial Population James C. H. Goh*, Siew Leng Low, and Shamal DasDe Department of Orthopaedic Surgery, National University of Singapore, Singapore Abstract Ethnic differences in bone density and hip geometry are known to exist, even within the same population. A recent study in Singapore showed that there were significant racial differences in hip fracture rates, with Chinese having the highest incidence of hip fractures. The aim of this study was to compare the bone mineral density (BMD) and hip axis length in Chinese, Malay, and Indian women. A total of 1575 women aged 20–59 yr were recruited, of which 77.6% (1222) were Chinese, 7.7% (122) Malays, and 14.7% (231) Indians. There was no significant difference in peak BMD of both lumbar spine and femoral neck among the three ethnic groups. However, in the older age group (50–59 yr), both Chinese and Malay women had significantly lower femoral neck BMD compared to Indian women. There was no significant loss in BMD of the lumbar spine between the second and fifth decades in all the three races. Between the second and fifth decade, Chinese and Malay women had significant bone loss in the femoral neck of 6.6% and 8.2%, respectively, whereas Indian women did not show any significant bone loss. Chinese women had significantly longer hip axis length compared to either Malay or Indian women (9.87 ± 0.52 cm vs 9.67 ± 0.49 cm; p < 0.005; and 9.69 ± 0.55 cm, p < 0.05, respectively). The initial findings suggest racial differences in bone density and hip geom- etry exist in the local community. Future research should include prospective, longitudinal studies to determine the age-related bone loss in these three racial groups. It is also important to investigate the differences of spine and hip fracture rates and their relationship with bone density and hip axis length. Key Words: Bone density; hip axis length; Chinese; Malay; Indian. Introduction Osteoporosis is becoming increasingly common in Asia as the population ages. It has been projected that 50% of all hip fractures in the world will occur in Asia (1). A recent study in Singapore showed that between 1960 and 1990, there was a fivefold increase in hip fracture rates in women (2). The study concluded that there were significant racial differences in hip fracture incidence rates, with Chinese having the highest inci- dence of hip fractures. One of the major risk factors for a hip fracture is low bone density and this suggests that there might be racial differences in bone mineral density (BMD) among the three races. The latest population census data showed the ethnic distri- bution in this country consists of 77% Chinese, 14% Malays, and 7.6% Indians. However, BMD studies in Singapore have been limited to the Chinese population, with no data reported on the other two ethnic groups (3,4). Peak BMD is one of the major determinants of BMD at older age and is used for T- score calculation. In the local population, it has not been estab- lished if Malay and Indian women have similar peak BMD compared to Chinese women. Apart from bone density, geometry of the hip (e.g., the shorter hip axis length) in Asians might account for the lower incidence of hip fractures compared to Caucasians (5,6). The hip geometry in Singapore women has not been studied and it Journal of Clinical Densitometry, vol. 7, no. 4, 406–412, 2004 © Copyright 2004 by Humana Press Inc. All rights of any nature whatsoever reserved. 1094-6950/04/7:406–412/$25.00 Original Article Received 04/30/03; Revised 04/20/04; Accepted 04/20/04 * Address correspondence to James Goh, Ph.D., Associate Professor, Department of Orthopaedic Surgery, National University of Singapore, Lower Kent Ridge Road, Singapore 119074. E-mail: dosgohj@nus.edu.sg 406