Osteoarthrosis of the knee in men and women in association with overweight, smoking, and hormone therapy

Objectives-The aim was to examine the relation between osteoarthrosis of the knee leading to prosthetic surgery among men and women and overweight, smoking, and hormone therapy. Methods-A case-referent study was performed with a study base of all men and women, born 1921-1938, living in 14 counties in Sweden during 1991-95. The cases (n=625) were identified through the Swedish Knee Arthroplasty Register. The referents (n=548) were randomly selected through the central population register from the same counties. Detailed information on general health status, height, weight, smoking habits, medication, use of hormones, specific physical loads from occupation and housework, and sports activities was collected by a telephone interview and a postal questionnaire. The cases were classified in terms of high, medium or low/non-exposure to the factors studied, according to the distribution of variables among the referents. Results-Women with high body mass index (BMI) at the age of 40 had a relative risk of 9.2 (95%CI 5.3, 16.0) of developing severe knee osteoarthrosis later in life, and for men at the same age the relative risk was 3.9 (95%CI 2.3, 6.4). Smokers were less likely to develop severe knee osteoarthrosis compared with nonsmokers. Oestrogen therapy for women over 50 showed an increased relative risk of 1.8 (95%CI 1.2, 2.6), while use of oral contraceptives did not influence the risk. Conclusion-Overweight is a risk factor for knee osteoarthrosis leading to prosthetic surgery in men and women, with the strongest relation for women. Oestrogen therapy after 50 increased the relative risk, while smoking decreased it.