The roles of adulthood behavioural factors and familial influences in bone density among men

Abstract

BACKGROUND: A primary strategy in osteoporosis prevention is advice on exercise, smoking, and calcium intake, although its practical value is unclear. AIM: To investigate the roles of such factors on bone density (BMD) after considering the influences of familial aggregation (combined effects of genetics and familial influences) in Finnish men 35-69 years old. METHODS: We selected 105 male monozygotic twin pairs, with discordance in suspected determinants. RESULTS: Dietary calcium was associated with BMD of the femoral neck; and body weight and lifetime frequency of endurance and ball game sport activities were associated with both femoral neck and lumbar BMD. Occupational loading and smoking were associated with neither. However, age and familial aggregation explained 73% of the variance of BMD in both the femoral neck and lumbar spine; calcium intake explained 1% in femoral neck and lifetime exercise 1% in lumbar spine. CONCLUSIONS: The effects of dietary calcium and physical activity that are not 'embedded' in the familial influences had very modest effects on the variance of BMD. Thus our chances of influencing BMD in later adulthood by targeting behavioural habits are likely to be limited. Interventions focused on childhood and the family unit may achieve more beneficial long-term results.