Effect of self-reported walking difficulty on bone mass and bone resorption marker in Japanese people aged 40 years and over

Background: This study aimed to examine the association of walking difficulty with bone mass or bone turnover among community-dwelling Japanese people aged 40 years and older. Methods: We studied 1097 community-dwelling Japanese people aged 40 years and older (379 men and 718 women) who were invited to participate in periodic health examinations in 2006-2009. Walking difficulty was defined as having difficulty walking 100 m on a level surface (self-administered questionnaire). Calcaneal stiffness index (bone mass) was measured by quantitative ultrasound. Spot urine samples were collected, and urinary N-terminal cross-linking telopeptide of type I collagen (NTx) was measured. Values were corrected for creatinine (Cre) concentration. Results: The prevalence of walking difficulty was significantly higher in women than in men (7.4 vs. 3.4 %, p = 0.011) and significantly increased with age in men (p for trend = 0.02) and women (p for trend <0.001). In univariate analysis, men and women with walking difficulty were older (p < 0.001) and had a lower stiffness index (p < 0.001), compared with those without walking difficulty. Among women, individuals with walking difficulty had significantly higher urinary NTx/Cre than those without walking difficulty (p < 0.001); however, this was not so among men (p = 0.39). Multiple regression analysis adjusted for age, weight, and menopausal status showed a significant association between walking difficulty and lower stiffness index in men (p = 0.004) and women (p = 0.005). In women, walking difficulty was significantly associated with higher NTx/Cre (p = 0.001), but not in men (p = 0.35). Conclusions: Walking difficulty may contribute to low bone mass in both sexes but might cause high bone turnover in women only.