Fracture Incidence With 6-9 Years of Daily School Physical Activity: Lower Relative Fracture Risk at the End of the Intervention But Not After.

Fractures pose a significant burden on society, making prevention strategies important. One approach is to increase physical activity (PA), which may enhance bone mass and muscle strength, thereby lowering fracture risk. A total of 3476 children who began 1st grade (mean age 7 years) between 1998 and 2012 in four Swedish schools were included. The intervention group was 1328 children from one school who received daily school PA (200 min/week, 5 lessons/week) for a mean of 6.9 (SD 1.3) years. Controls were 2148 age-matched children in three schools who received the Swedish standard of PA (60 min/week, 1-2 lessons/week). Fractures were identified in the regional radiographic archives. Participants were followed until death or study end (2024-08-31). Participants who migrated from the region were excluded during periods away. This resulted in a mean follow-up period of 8.2 (SD 4.3) years after the intervention. We used incidence rate ratios (IRRs) to express differences between groups. We identified 1278 fractures in 1225 events. IRR (intervention group compared to controls) was in lower primary (ages 7-9) 1.22 (95% confidence interval (CI) 0.93-1.60), in upper primary (ages 10-12) 1.14 (95% CI 0.91-1.43), and in lower secondary (ages 13-15) 0.78 (95% CI 0.61-0.99). After the intervention (ages 16-30), IRR was 1.04 (95% CI 0.85-1.27). The study indicates that daily school PA initiated at age 7 is associated with a lower relative fracture risk at the end of the intervention (ages 13-15) but not after termination of the intervention. Our data indicate that daily school PA may possibly be one method to decrease fracture risk during peak fracture incidence at growth.