Midlife physical activity, BMI, and hip fracture risk five decades later in men: a NOREPOS study

Research on hip fracture prevention in men is limited. In men, physical activity and body mass index were independently and jointly associated with hip fracture risk, with the highest risk among inactive and thin men. Promoting exercise and healthy weight in midlife may reduce fracture burden and support healthy ageing.

Hip fractures predominantly affect older people with frailty. The incidence increases with age, and the number is expected to increase substantially due to population aging. Physical inactivity and low body mass index (BMI) are key modifiable risk factors for hip fractures. This study aimed to explore the associations of physical activity and BMI with long-term hip fracture risk in men.

This prospective cohort study included 12,900 men aged 40-49 years from the Oslo study 1972-1973. A questionnaire assessed physical activity, whereas height and weight were measured. Hip fractures were identified through linkage to a national database. Cox regression calculated adjusted hazard ratios (HR) with 95% confidence intervals (CI) for hip fracture according to physical activity level. A secondary analysis examined a composite variable combining activity level (inactive/active) and BMI (< 22/22-24.9/ ≥ 25 kg/m²).

During 195,384 person-years of follow-up, 1542 men (12%) sustained a hip fracture at a median age of 82 years. Inactive men had a 38% higher risk (HR 1.38 [95% CI 1.16-1.63]) than active men. Active men had a lower hip fracture risk across all categories of BMI, while the greatest risk was found in inactive men with a BMI < 22 kg/m², HR 1.79 [95% CI 1.36-2.35] compared to active men with a BMI ≥ 25.

Physical inactivity and low BMI in midlife were independently associated with increased long-term hip fracture risk. Inactive and thin men had the greatest risk, suggesting that maintaining physical activity in mid-life is important for healthy ageing and independence.