THE TROMSO STUDY - PHYSICAL-ACTIVITY AND THE INCIDENCE OF FRACTURES IN A MIDDLE-AGED POPULATION

We have studied the relation of occupational and recreational physical activity to fractures at different locations. All men born between 19 25 and 1959 and all women born between 1930 and 1959 in the city of Tr omso were invited to participate in surveys in 1979-1980 and 1986-1987 (The Tromso Study). Of 16,676 invited persons, 12,270 (73.6%) attende d both surveys. All nonvertebral fractures (n = 1435) sustained from 1 988 to 1995 were registered in the only hospital in the area. Average age in the middle of the follow-up period (December 31, 1991) was 47.3 years among men and 45.1 years among women, ranging from 32 to 66 yea rs. Fracture incidence increased with age at all locations among women , but it decreased with or was independent of age among men. Low-energ etic fractures constituted 74.4% of all fractures among women and 55.2 % among men. When stratifying by fracture location, the most physicall y active persons among those 45 years or older suffered fewer fracture s in the weight-bearing skeleton (relative risk [RR] 0.6, confidence i nterval [CI] 0.4-0.9, age-adjusted), but not in the non-weight-bearing skeleton (RR 1.0, CI 0.7-1.2, age-adjusted) compared with sedentary p ersons. The relative risk of a low-energetic fracture in the weight-be aring skeleton among the most physically active middle-aged was 0.3 (C I 0.1- 0.7) among men and 0.9 (CI 0.4-1.8) among women compared with t he sedentary when adjusted for age, body mass index, body height, toba cco smoking, and alcohol and milk consumption. It seems that the benef icial effect on the skeleton of weight-bearing activity is reflected a lso in the incidence of fractures at different sites.