Postmenopausal Weight Change and Incidence of Fracture
Objectives To determine associations between postmenopausal change in body weight and incidence of fracture and associations between voluntary and involuntary weight loss and risk of fracture.
Design Post hoc analysis of data from the Women’s Health Initiative Observational Study and Clinical Trials.
Setting 40 clinical centers in the United States.
Participants 120 566 postmenopausal women, aged 50-79 at baseline (1993-98), followed through 2013 (mean fracture follow-up duration 11 years from baseline).
Exposures Annualized percentage change in measured body weight from baseline to year 3, classified as stable (<5% change), weight loss (≥5%), or weight gain (≥5%). Self assessment of whether weight loss was intentional or unintentional. Cox proportional hazards regression models were adjusted for age, race/ethnicity, baseline body mass index (BMI), smoking, alcohol intake, level of physical activity, energy expenditure, calcium and vitamin D intake, physical function score, oophorectomy, hysterectomy, previous fracture, comorbidity score, and drug use.
Main outcomes Incident self reported fractures of the upper limbs, lower limbs, and central body; hip fractures confirmed by medical records.
Results Mean participant age was 63.3. Mean annualized percent weight change was 0.30% (95% confidence interval 0.28 to 0.32). Overall, 79 279 (65.6%) had stable weight; 18 266 (15.2%) lost weight; and 23 021 (19.0%) gained weight. Compared with stable weight, weight loss was associated with a 65% higher incidence rates of fracture in hip (adjusted hazard ratio 1.65, 95% confidence interval 1.49 to 1.82), upper limb (1.09, 1.03 to 1.16), and central body (1.30, 1.20 to 1.39); weight gain was associated with higher incidence rates of fracture in upper limb (1.10, 1.05 to 1.18) and lower limb (1.18, 1.12 to 1.25). Compared with stable weight, unintentional weight loss was associated with a 33% higher incidence rates of hip fracture (1.33, 1.19 to 1.47) and increased incidence rates of vertebral fracture (1.16, 1.06 to 1.26); intentional weight loss was associated with increased incidence rates of lower limb fracture (1.11, 1.05 to 1.17) and decreased incidence of hip fracture (0.85, 0.76 to 0.95).
Conclusions Weight gain, weight loss, and intentional weight loss are associated with increased incidence of fracture, but associations differ by fracture location. Clinicians should be aware of fracture patterns after weight gain and weight loss.
The influence of body weight on the risk of fracture is complex. Low body weight is considered a risk factor for osteoporotic fracture. There is, however, increasing recognition that a high proportion of postmenopausal women with low trauma fractures are obese. Moreover, beyond low body weight per se, change in body weight can have an important influence on risk of fracture. For example, longitudinal studies of postmenopausal white women in the United States have found that weight loss increases the risk of subsequent hip and other frailty fractures. Similar studies of postmenopausal non-white women are lacking, yet differences in body weight distributions and absolute risk of fracture8 across racial groups are striking.
There is also a paucity of information on whether the influence of weight change on subsequent risk of fracture varies by anatomical site. In longitudinal studies of white women aged ≥65, weight loss measured in various ways (over four years or since maximum weight or since age 50) was associated with an increased risk of hip fracture, whereas weight gain since age 25 was associated with a higher risk of ankle fracture. No longitudinal studies, however, have focused specifically on how weight change can differentially influence upper limb, lower limb, hip, and central body fractures among postmenopausal white or non-white women in the US. Also, few studies have considered the reason for underlying weight loss in the analysis of associations between weight loss and fractures. This distinction might be important because serious illness could be an underlying cause of both involuntary weight loss and osteoporosis. In one study, associations between weight loss and increased risk of frailty fracture were significant only among women reporting involuntary, but not voluntary weight loss, whereas in another study, voluntary and involuntary weight loss among overweight women were each associated with similar (2.5-fold) increases in risk of hip fracture. Neither of those two studies adjusted for baseline weight or body mass index (BMI).
We investigated associations between change in body weight (baseline to third annual visit) and subsequent incidence of fracture classified by anatomical region (for example, upper limb, lower limb, central body) among postmenopausal women and to what extent self reported voluntary and involuntary weight loss are associated with increased incidence of fracture. We hypothesized that associations between weight loss and increased fracture incidence would be more pronounced for hip fractures than for limb fractures because of the potential loss in soft tissue padding around the hip that could counteract traumatic forces. We also hypothesized that even voluntary weight loss would be associated with an increased incidence of hip fracture. We further postulated that weight gain would increase the incidence of limb fractures, as the upper and lower extremities have little overlying soft tissue to absorb the increased impact resulting from weight gain and because of poor neuromuscular conditioning.
Abstract and Introduction
Abstract
Objectives To determine associations between postmenopausal change in body weight and incidence of fracture and associations between voluntary and involuntary weight loss and risk of fracture.
Design Post hoc analysis of data from the Women’s Health Initiative Observational Study and Clinical Trials.
Setting 40 clinical centers in the United States.
Participants 120 566 postmenopausal women, aged 50-79 at baseline (1993-98), followed through 2013 (mean fracture follow-up duration 11 years from baseline).
Exposures Annualized percentage change in measured body weight from baseline to year 3, classified as stable (<5% change), weight loss (≥5%), or weight gain (≥5%). Self assessment of whether weight loss was intentional or unintentional. Cox proportional hazards regression models were adjusted for age, race/ethnicity, baseline body mass index (BMI), smoking, alcohol intake, level of physical activity, energy expenditure, calcium and vitamin D intake, physical function score, oophorectomy, hysterectomy, previous fracture, comorbidity score, and drug use.
Main outcomes Incident self reported fractures of the upper limbs, lower limbs, and central body; hip fractures confirmed by medical records.
Results Mean participant age was 63.3. Mean annualized percent weight change was 0.30% (95% confidence interval 0.28 to 0.32). Overall, 79 279 (65.6%) had stable weight; 18 266 (15.2%) lost weight; and 23 021 (19.0%) gained weight. Compared with stable weight, weight loss was associated with a 65% higher incidence rates of fracture in hip (adjusted hazard ratio 1.65, 95% confidence interval 1.49 to 1.82), upper limb (1.09, 1.03 to 1.16), and central body (1.30, 1.20 to 1.39); weight gain was associated with higher incidence rates of fracture in upper limb (1.10, 1.05 to 1.18) and lower limb (1.18, 1.12 to 1.25). Compared with stable weight, unintentional weight loss was associated with a 33% higher incidence rates of hip fracture (1.33, 1.19 to 1.47) and increased incidence rates of vertebral fracture (1.16, 1.06 to 1.26); intentional weight loss was associated with increased incidence rates of lower limb fracture (1.11, 1.05 to 1.17) and decreased incidence of hip fracture (0.85, 0.76 to 0.95).
Conclusions Weight gain, weight loss, and intentional weight loss are associated with increased incidence of fracture, but associations differ by fracture location. Clinicians should be aware of fracture patterns after weight gain and weight loss.
Introduction
The influence of body weight on the risk of fracture is complex. Low body weight is considered a risk factor for osteoporotic fracture. There is, however, increasing recognition that a high proportion of postmenopausal women with low trauma fractures are obese. Moreover, beyond low body weight per se, change in body weight can have an important influence on risk of fracture. For example, longitudinal studies of postmenopausal white women in the United States have found that weight loss increases the risk of subsequent hip and other frailty fractures. Similar studies of postmenopausal non-white women are lacking, yet differences in body weight distributions and absolute risk of fracture8 across racial groups are striking.
There is also a paucity of information on whether the influence of weight change on subsequent risk of fracture varies by anatomical site. In longitudinal studies of white women aged ≥65, weight loss measured in various ways (over four years or since maximum weight or since age 50) was associated with an increased risk of hip fracture, whereas weight gain since age 25 was associated with a higher risk of ankle fracture. No longitudinal studies, however, have focused specifically on how weight change can differentially influence upper limb, lower limb, hip, and central body fractures among postmenopausal white or non-white women in the US. Also, few studies have considered the reason for underlying weight loss in the analysis of associations between weight loss and fractures. This distinction might be important because serious illness could be an underlying cause of both involuntary weight loss and osteoporosis. In one study, associations between weight loss and increased risk of frailty fracture were significant only among women reporting involuntary, but not voluntary weight loss, whereas in another study, voluntary and involuntary weight loss among overweight women were each associated with similar (2.5-fold) increases in risk of hip fracture. Neither of those two studies adjusted for baseline weight or body mass index (BMI).
We investigated associations between change in body weight (baseline to third annual visit) and subsequent incidence of fracture classified by anatomical region (for example, upper limb, lower limb, central body) among postmenopausal women and to what extent self reported voluntary and involuntary weight loss are associated with increased incidence of fracture. We hypothesized that associations between weight loss and increased fracture incidence would be more pronounced for hip fractures than for limb fractures because of the potential loss in soft tissue padding around the hip that could counteract traumatic forces. We also hypothesized that even voluntary weight loss would be associated with an increased incidence of hip fracture. We further postulated that weight gain would increase the incidence of limb fractures, as the upper and lower extremities have little overlying soft tissue to absorb the increased impact resulting from weight gain and because of poor neuromuscular conditioning.
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