Risk factors for nonvertebral fracture in obese older women

CONTEXT

A high prevalence of obesity has recently been reported in postmenopausal women with low trauma fracture, suggesting that higher bone mineral density (BMD) in obese individuals may not be protective against fracture.

OBJECTIVE

The aim of this study was to compare BMD and other risk factors for nonvertebral fracture in 1377 obese postmenopausal women.

DESIGN

Characteristics of obese women with and without incident nonvertebral fracture were investigated among the prospective cohort in the Study of Osteoporotic Fractures.

SETTING

The Study of Osteoporotic Fractures is a multicenter study of 9704 women (>99% Caucasian) aged 65 yr and over who were recruited between September 1986 and October 1988 from population-based listings at four U.S. clinical centers.

MAIN OUTCOME MEASURE

The main outcome measure was nonvertebral fracture.

RESULTS

BMD T-scores in the spine, femoral neck, and total hip were significantly lower in obese women who experienced fractures than in obese women without fracture: mean differences, -0.56 [95% confidence interval (CI) = -0.73 to -0.39], -0.46 (95% CI = -0.57 to -0.36), and -0.51 (95% CI = -0.62 to -0.39), respectively (P < 0.0001 for all). A previous history of fracture [odds ratio = 1.69 (95% CI = 1.33-2.14); P < 0.0001] and femoral neck BMD [1.62 (95% CI = 1.42-1.85) per sd decrease in BMD; P < 0.0001] were independently associated with incident nonvertebral fracture.

CONCLUSIONS

Obese postmenopausal women who sustain nonvertebral fractures have significantly lower BMD on average than obese women without fracture and are more likely to have a past history of fracture. Fractures in obese postmenopausal women thus exhibit some characteristics of fragility fractures.

Osteoprotegerin Lys3Asn polymorphism and the risk of fracture in older women

CONTEXT

Osteoprotegerin (OPG) is a soluble decoy receptor for receptor activator nuclear factor kappa-beta that blocks osteoclastic bone resorption.

OBJECTIVE

We investigated the association between a Lys3Asn polymorphism in the OPG gene and bone mineral density (BMD), and the risk of fracture in 6695 women aged 65 yr and older participating in the Study of Osteoporotic Fractures.

DESIGN

BMD was measured using either single-photon absorptiometry (Osteon Osteoanalyzer; Dove Medical Group, Los Angeles, CA) or dual-energy x-ray absorptiometry (Hologic QDR 1000; Hologic, Inc., Bedford, MA). Incident fractures were confirmed by physician adjudication of radiology reports. Genotyping was performed using an immobilized probe-based assay.

RESULTS

Women who were homozygous for the minor G (Lys) allele had significantly lower BMD at the intertrochanter, distal radius, lumbar spine, and calcaneus than those with the C (Asn) allele. There were 701 incident hip fractures during 13.6-yr follow-up (91,249 person-years), including 362 femoral neck and 333 intertrochanteric hip fractures. Women with the C/C (Asn-Asn) genotype had a 51% higher risk of femoral neck fracture (95% confidence interval, 1.13-2.02) and 26% higher risk of hip fracture (95% confidence interval, 1.02-1.54) than those with the G/G (Lys-Lys) genotype. These associations were independent of BMD. Intertrochanteric fractures were not associated with the Lys3Asn polymorphism.

CONCLUSION

These results require confirmation but suggest a role for the OPG Lys3Asn polymorphism in the genetic susceptibility to hip fractures among older white women.

Tumor necrosis factor-alpha polymorphism, bone strength phenotypes, and the risk of fracture in older women

TNFalpha is a proinflammatory cytokine that promotes osteoclastic bone resorption. We evaluated the association between a G-308A polymorphism (rs1800629) at the TNFA locus and osteoporosis phenotypes in 4306 older women participating in the Study of Osteoporotic Fractures. Femoral neck bone mineral density (BMD) and structural geometry were measured using dual-energy x-ray absorptiometry and hip structural analysis. Incident fractures were confirmed by physician adjudication of radiology reports. Despite similar femoral neck BMD, women with the A/A genotype had greater subperiosteal width (P = 0.01) and endocortical diameter (P = 0.03) than those with the G/G genotype. The net result of these structural differences was that there was a greater distribution of bone mass away from the neutral axis of the femoral neck in women with the A/A genotype, resulting in greater indices of bone bending strength (cross-sectional moment of inertia: P = 0.004; section modulus: P = 0.003). Among 376 incident hip fractures during 12.1 yr of follow-up, a 22% decrease in the risk of hip fracture was seen per copy of the A allele (relative risk 0.78; 95% confidence interval 0.63, 0.96), which was not influenced by adjustments for potential confounding factors, BMD, or bone strength indices. The G-308A polymorphism was not associated with a reduced risk of other fractures. These results suggest a potential role of genetic variation in TNFalpha in the etiology of osteoporosis.

Characteristics of an adult population with newly diagnosed type 2 diabetes: the relation of obesity and age of onset

OBJECTIVE

To determine whether adults diagnosed with type 2 diabetes at 18-44 years of age (early type 2 diabetes) have different metabolic profiles at diagnosis than adults diagnosed at > or =45 years of age (usual type 2 diabetes).

RESEARCH DESIGN AND METHODS

Within a health maintenance organization, we studied characteristics among 2,437 adults newly diagnosed with type 2 diabetes between 1996 and 1998 who had measured weight, HbA(1c), blood pressure, and cholesterol within 3 months of diagnosis. We abstracted clinical data from electronic medical records. We compared mean and proportional differences with parametric t tests and chi(2) analyses, respectively. We used multiple logistic regression to identify the factors independently associated with the onset group (early vs. usual type 2 diabetes).

RESULTS

There was an inverse linear relationship between BMI and age at diagnosis of type 2 diabetes (P < 0.001). On univariate analysis, adults with early type 2 diabetes were more obese (BMI 39 vs. 33 kg/m(2), P < 0.001), were more likely to be female (P = 0.04), had slightly worse glycemic control (HbA(1c) 7.7 vs. 7.5%, P = 0.03), had a higher prevalence of diastolic hypertension (37 vs. 26%, P < 0.001), despite a lower prevalence of systolic hypertension (34 vs. 55%, P < 0.001), and had an equally high rate of abnormal lipids (82 vs. 78%, P = 0.13) than adults with usual type 2 diabetes. BMI, female gender, cholesterol, and diastolic and systolic blood pressure remained independently associated with onset group at multivariate analysis.

CONCLUSIONS

Although both onset groups were on average obese, the inverse linear relationship of obesity and age of diabetes onset that we observed suggests that obesity is a continuous risk rather than a threshold risk for diabetes onset. Both onset groups had a high prevalence of cardiovascular disease risk factors.

Congestive heart failure in type 2 diabetes: prevalence, incidence, and risk factors

OBJECTIVE

To estimate the prevalence and incidence of congestive heart failure (CHF) in populations with and without type 2 diabetes and to identify risk factors for diabetes-associated CHF.

RESEARCH DESIGN AND METHODS

We searched the inpatient and outpatient electronic medical records of 9,591 individuals diagnosed with type 2 diabetes before 1 January 1997 and those of an age- and sex-matched control group without diabetes for a diagnosis of CHF. Among those without a baseline diagnosis of CHF, we searched forward for 30 months for incident cases of CHF. We constructed multiple logistic regression models to identify risk factors for both prevalent and incident CHF.

RESULTS

CHF was prevalent in 11.8% (n = 1,131) of diabetic subjects and 4.5% (n = 435) of control subjects at baseline. We observed incident cases of CHF in 7.7% of diabetic subjects free of CHF at baseline (650 of 8,460) and in 3.4% of control subjects (314 of 9,156). In diabetic subjects, age, diabetes duration, insulin use, ischemic heart disease, and elevated serum creatinine were independent risk factors for both prevalent and incident CHF. Better glycemic control at baseline, and improved glycemic and blood pressure control at follow-up predicted the development of CHF.

CONCLUSIONS

Despite controlling for age, duration of diabetes, presence of ischemic heart disease, and presence of hypertension, insulin use was associated with both prevalent and incident CHF. Why insulin use and better glycemic control both at baseline and follow-up independently predicted CHF deserves further study.

Predictors of glycemic control in insulin-using adults with type 2 diabetes

OBJECTIVE

To determine the characteristics that influence glycemic control among insulin-using adults with type 2 diabetes.

RESEARCH DESIGN AND METHODS

We studied all 1,333 eligible members of a large not-for-profit health maintenance organization who responded to a 1997 survey. We tested associations among demographic, treatment, and psychometric variables with mean 1997 HbA1c values. The Problem Areas in Diabetes (PAID) instrument was used to assess the emotional effect of living with diabetes, and the Short Form 12 Physical Function Scale was used to assess the effect of physical limitations on daily activities. Based on differences between and within treatment groups, we built models to predict glycemic control for subgroups of subjects who were using insulin alone and those who were using insulin in combination with an oral hypoglycemic agent.

RESULTS

Younger age, lower BMI, and increased emotional distress about diabetes (according to the PAID scale) were all significant predictors (P < 0.05) of worse glycemic control. However, except among individuals with an HbA1c level of >8.0 who were receiving combination therapy, only approximately 10% of the variance in glycemic control could be predicted by demographic, treatment, or psychometric characteristics.

CONCLUSIONS

Personal characteristics explain little of the variation in glycemic control in insulin-using adults with type 2 diabetes. Possible explanations are that the reduced complexity of control in type 2 diabetes makes the disease less sensitive to personal factors than control in type 1 diabetes, that health-related behavior is less driven by personal and environmental characteristics among older individuals, or that, in populations exposed to aggressive glycemic control with oral hypoglycemic agents and nurse care managers, personal differences become largely irrelevant.

Hyponatremia: evaluating the correction factor for hyperglycemia

PURPOSE

There are no controlled experimental data that assess the accuracy of the commonly used correction factor of a 1.6 meq/L decrease in serum sodium concentration for every 100 mg/dL increase in plasma glucose concentration. The purpose of this study was to evaluate experimentally the hyponatremic response to acute hyperglycemia.

SUBJECTS AND METHODS

Somatostatin was infused to block endogenous insulin secretion in 6 healthy subjects. Plasma glucose concentrations were increased to >600 mg/dL within 1 hour by infusing 20% dextrose. The glucose infusion was then stopped and insulin given until the plasma glucose concentration decreased to 140 mg/dL. Plasma glucose and serum sodium concentrations were measured every 10 minutes.

RESULTS

Overall, the mean decrease in serum sodium concentration averaged 2.4 meq/L for every 100 mg/dL increase in glucose concentration. This value is significantly greater than the commonly used correction factor of 1.6 (P = 0.02). Moreover, the association between sodium and glucose concentrations was nonlinear. This was most apparent for glucose concentrations >400 mg/dL. Up to 400 mg/dL, the standard correction of 1.6 worked well, but if the glucose concentration was >400 mg/dL, a correction factor of 4.0 was better.

CONCLUSION

These data indicate that the physiologic decrease in sodium concentration is considerably greater than the standard correction factor of 1.6 (meq/L Na per 100 mg/dL glucose), especially when the glucose concentration is >400 mg/dL. Additionally, a correction factor of a 2.4 meq/L decrease in sodium concentration per 100 mg/dL increase in glucose concentration is a better overall estimate of this association than the usual correction factor of 1.6.

Extreme hyperinsulinemia unmasks insulin's effect to stimulate protein synthesis in the human forearm

Insulin clearly stimulates skeletal muscle protein synthesis in vitro. Surprisingly, this effect has been difficult to reproduce in vivo. As in vitro studies have typically used much higher insulin concentrations than in vivo studies, we examined whether these concentration differences could explain the discrepancy between in vitro and in vivo observations. In 14 healthy volunteers, we raised forearm insulin concentrations 1,000-fold above basal levels while maintaining euglycemia for 4 h. Amino acids (AA) were given to either maintain basal arterial (n = 4) or venous plasma (n = 6) AA or increment arterial plasma AA by 100% (n = 4) in the forearm. We measured forearm muscle glucose, lactate, oxygen, phenylalanine balance, and [3H]phenylalanine kinetics at baseline and at 4 h of insulin infusion. Extreme hyperinsulinemia strongly reversed postabsorptive muscle's phenylalanine balance from a net release to an uptake (P < 0.001). This marked anabolic effect resulted from a dramatic stimulation of protein synthesis (P < 0.01) and a modest decline in protein degradation. Furthermore, this effect was seen even when basal arterial or venous aminoacidemia was maintained. With marked hyperinsulinemia, protein synthesis increased further when plasma AA concentrations were also increased (P < 0.05). Forearm blood flow rose at least twofold with the combined insulin and AA infusion (P < 0.01), and this was consistent in all groups. These results demonstrate an effect of high concentrations of insulin to markedly stimulate muscle protein synthesis in vivo in adults, even when AA concentrations are not increased. This is similar to prior in vitro reports but distinct from physiological hyperinsulinemia in vivo where stimulation of protein synthesis does not occur. Therefore, the current findings suggest that the differences in insulin concentrations used in prior studies may largely explain the previously reported discrepancy between insulin action on protein synthesis in adult muscle in vivo vs. in vitro.

Physicians as patients. Choices regarding their own resuscitation

BACKGROUND

Attitudes toward cardiopulmonary resuscitation have changed considerably during the last 30 years. Although physicians are routinely involved in the decision making about cardiopulmonary resuscitation for their patients, little is known about their collective preferences regarding it for themselves.

METHODS

A questionnaire was distributed at an internal medicine primary care review course at an urban community hospital. Of the 111 physicians registered at the meeting, 72 (65%) completed the questionnaire and serve as the basis for the results. Physicians were asked if they would want cardiopulmonary resuscitation for themselves in the presence of an acute myocardial infarction, Alzheimer's disease, and nine other advanced chronic diseases at the projected ages of 40, 60, and 80 years.

RESULTS

At all projected ages, physicians' desire for cardiopulmonary resuscitation with any advanced chronic disease was significantly less than with an acute myocardial infarction (P < or = .000001 except for rheumatoid arthritis). Fewer physicians wanted cardiopulmonary resuscitation at age 80 years than at 40 years for any disease (P < or = .002). The results did not differ when analyzed by respondents' age, gender, or primary care specialty, or the size of the community in which they practiced.

CONCLUSIONS

The results of this initial survey indicate that most physicians would not want cardiopulmonary resuscitation with a variety of underlying chronic diseases and corresponding functional impairments--particularly with advancing age. Conversely, with an acute myocardial infarction, all physicians surveyed would desire cardiopulmonary resuscitation at age 40 years, and many would continue to desire it with advancing age.