Cross-sectional associations between accelerometer-measured physical activity and hip bone mineral density: the Tromsø Study 2015-2016.

Positive associations between physical activity and bone health have been found in population-based studies, however, mostly based on self-reported physical activity. Therefore, we investigated the association between accelerometer-measured physical activity, measured in steps per day and minutes of moderate to vigorous physical activity (MVPA) per day, and total hip areal BMD (aBMD) measured by DXA in a general population, utilizing multiple regression models. The study participants, 1560 women and 1177 men aged 40-84 yr, were part of the seventh survey of the Tromsø Study (2015-2016). In both genders, we found a positive association between the number of daily steps and aBMD adjusted for age, BMI, and smoking status (P < .001). In women, an increase of 1000 steps per day was associated with 0.005 g/cm2 higher aBMD. For men, a polynomial curve indicated a positive association with aBMD up to 5000 steps per day, plateauing between 5000 and 14 000 steps, and then increasing again. Additionally, MVPA duration was positively associated with aBMD in both women (P < .001) and men (P = .004) when adjusted for age, BMI, and smoking status. Specifically, each 60-min increase in daily MVPA was associated with 0.028 and 0.023 g/cm2 higher aBMD in women and men, respectively. Despite positive associations, the clinical impact of physical activity on aBMD in this general population of adults and older adults was relatively small, and a large increase in daily MVPA might not be achievable for most individuals. Therefore, further longitudinal population-based studies incorporating device-based measures of physical activity could add more clarity to these relationships.

A 15-year follow-up study of hip bone mineral density and associations with leisure time physical activity. The Tromsø Study 2001-2016.

AIMS: The aim was to investigate the long-term association between leisure time physical activity and hip areal bone mineral density (aBMD), in addition to change in hip aBMD over time, in 32-86 years old women and men. METHODS: Data were retrieved from the 2001, 2007-2008, and 2015-2016 surveys of the Tromsø Study, a longitudinal population study in Norway. Leisure time physical activity was assessed by the four-level Saltin-Grimby Physical Activity Level Scale which refers to physical exertion in the past twelve months. Hip aBMD was assessed by Dual-Energy X-ray Absorptiometry. Linear Mixed Model analysis was used to examine long-term associations between physical activity and hip aBMD (n = 6324). In addition, the annual change in hip aBMD was analyzed in a subsample of 3199 participants. RESULTS: Physical activity was significantly and positively associated with total hip aBMD in the overall cohort (p<0.005). Participants who reported vigorous activity had 28.20 mg/cm2 higher aBMD than those who were inactive (95% CI 14.71; 41.69, controlled for confounders), and even light physical activity was associated with higher aBMD than inactivity (8.32 mg/cm2, 95% CI 4.89; 11.76). Associations between physical activity and femoral neck aBMD yielded similar results. Hip aBMD decreased with age in both sexes, although more prominently in women. From 2001 to 2007-2008, aBMD changed by -5.76 mg/cm2 per year (95% CI -6.08; -5.44) in women, and -2.31 mg/cm2 (95% CI -2.69; -1.93), in men. From 2007-2008 to 2015-2016, the change was -4.45 mg/cm2 per year (95% CI -4.84; -4.06) in women, and -1.45 mg/cm2 (95% CI -1.92; -0.98) in men. CONCLUSIONS: In this cohort of adult men and women, physical activity levels were positively associated with hip aBMD in a dose-response relationship. Hip aBMD decreased with age, although more pronounced in women than men.

A cross-sectional and 6-year follow-up study of associations between leisure time physical activity and vertebral fracture in adults.

INTRODUCTION: Vertebral fractures are common osteoporotic fractures, affecting 2-46% of the population, causing morbidity and increased risk of mortality. Physical activity has beneficial effects for bone health, including increased bone mineral density and reduced hip fractures. However, evidence concerning prevention of vertebral fractures is scarce. Therefore, the aim of this study was to investigate the association between leisure time physical activity and vertebral fracture risk. METHODS: The data were retrieved from the 2001 and 2007-2008 surveys of the Tromsø Study, a longitudinal population study in Norway. A total of 1904 participants (1030 women and 874 men, age 38-87 yr and 40-87 yr respectively) were included in the cross-sectional analysis (2007-2008). Prospective follow-up data (2001 to 2007) on physical activity were available for 1131 participants (636 women and 495 men, age 32-69 yr and 33-69 yr respectively). Physical activity was assessed by a questionnaire and vertebral fracture by lateral vertebral fracture assessment from dual-energy x-ray absorptiometry scans. Logistic regression was used to examine associations between physical activity and vertebral fracture. RESULTS: After controlling for confounders (age, height, weight, smoking, osteoporosis, osteoporosis medication, left hip total bone mineral density, and use of hormones in women only), no cross-sectional associations between physical activity levels and vertebral fracture were observed, OR 1.13 (95% CI: 0.59-2.13), for moderately active women and 1.44 (0.61-3.42) for highly active women, compared with sedentary women. In men, the respective ORs were 1.74 (95% CI: 0.91-3.35) and 1.64 (0.78-3.41). In the prospective analyses, OR for vertebral fracture in women with reduced physical activity was 0.81 (95% CI: 0.18-3.62), 1.24 (95% CI: 0.29-5.26) for increased physical activity and 1.54 (95% CI: 0.43-5.50) for active unchanged physical activity pattern, compared with sedentary unchanged physical activity. In men, the respective ORs were 2.05 (95% CI: 0.57-7.42), 2.23 (95% CI: 0.63-7.87), and 1.81 (95% CI: 0.54-6.02). Subanalyses of women and men ≥50 yr showed similar results. CONCLUSIONS: Our findings suggest that physical activity does not play a major role in preventing vertebral fractures in Norwegian adults. Future studies may benefit from data on incident vertebral fracture, and objectively measured physical activity.