PHILADELPHIA, PA -- November 1, 2000 -- Women who are older or who have a high body mass index are at greater risk of developing hip osteoarthritis, leading to total hip replacement, according to a prospective analysis.

The findings were presented at the 64th Annual Scientific Meeting of the American College of Rheumatology (ACR) in Philadelphia, Pennsylvania.

The general risk factors for osteoarthritis (OA) in women (age, increased body mass index [BMI], physical activity and post-menopausal hormone replacement use) have previously not been well established specifically for hip OA.

Researchers from United States and Germany, led by Elizabeth W. Karlson, MD, of the rheumatology/immunology department at Brigham and Women's Hospital, Boston, Massachusetts, analysed the Nurses' Health Study to establish specific correlations for risk.

From the study, a cohort of women was chosen who had hip OA that was severe enough to require total hip replacement. From the original longitudinal cohort (121,700 women), 567 women reported having had a total hip replacement on questionnaires from 1990-1998, and had primary hip OA exclusive of rheumatoid arthritis (RA), congenital hip dysplasia, fracture or avascular necrosis.

Logistical regression models were used to assess the relationship of potential risk factors and primary hip OA leading to total hip replacement.

Age was significantly associated with an increased risk of hip OA, noted Dr. Karlson. Using five-year age categories, the highest quintile of age was associated with the highest relative risk (RR) of hip OA (RR = 38.6).

Increasing BMI was associated with increasing risk of hip OA; the highest quintile of BMI (over 35) was associated with an RR of 2.6. Additionally, the highest quintile of BMI at age 18 was associated with an even higher RR of 5.8.

There was no association between hip OA and recreational physical activity, nor with pre- or post-menopausal hormone use in this cohort.