Bone dimensional change with age: interactions of genetic, hormonal, and body size variables

Changes in bony dimensions with age were assessed longitudinally from standardized X-ray films in 170 middle-aged Caucasian women, starting at age 40 years and with a median duration of observation of 21.125 years. Consistent with earlier work, cortical area of the metacarpals and radial shaft declined with age at rates ranging from 0.57 to 0.86%/year. As predicted, estrogen replacement therapy decreased this loss in a dose-dependent manner. Not previously reported is the fact that weight gain over the period of observation reduced upper extremity bone loss. Moreover, this protection was independent of the estrogen effect. In contrast with bone loss in the upper extremity, both femur shaft diameter and femur shaft cortical area increased significantly with age (0.23 and 0.26%/year, respectively). Estrogen replacement therapy inhibited femur shaft expansion but had no effect on femur cortical area. Weight change, however, strongly influenced gain (or loss) of femur cortical area: those in the highest weight change tertile gained 4 times as much cortical area as those in the lowest weight change tertile. VDR genotype also significantly influenced femoral shaft changes: women with the bb genotype had both greater shaft expansion and a greater increase in cortical area. The VDR effects were independent of the effects of weight change and estrogen. Femoral shaft expansion was of sufficient magnitude to suggest that the mechanical properties of the entire femur may change appreciably with age. Finally, contrary to widespread belief, there was significant, if modest, expansion at the femoral neck with age.

Correcting calcium nutritional deficiency prevents spine fractures in elderly women

We tested the spine antifracture and bone sparing efficacy of 1.2 g/day of oral calcium as carbonate in two groups of elderly women, one with prevalent fractures (PF, n = 94) on entry and the other without (NPF, n = 103). It was a prospective randomized, double-blind, placebo-controlled trial in mostly rural communities in women over age 60 who were living independently and were consuming < 1 g/day of calcium. We obtained annual lateral spine radiographs and semiannual forearm bone density over 4.3 +/- 1.1 years and determined vertebral fractures by radiographic morphometry augmented by physician assessment. In the PF group, 15 of 53 subjects on calcium had incident fractures, compared with 21 of 41 on placebo (p = 0.023, chi2). Calcium did not reduce the rate of incident fractures in the NPF group. Those with a prevalent fracture on entry and not treated with calcium were 2.8 times more likely to experience an incident fracture than all others. Change in the forearm bone mass on placebo in the PF group was -1.24 +/- 2.41%/year compared with +0.31 +/- 1.80%/year on calcium (p < 0.001). In the NPF group, the difference was less: -0.39 +/- 2.08%/year versus 0.00 +/- 1.64%/year (p = 0.2). We conclude that in elderly postmenopausal women with spine fractures and selfselected calcium intakes of < 1 g/day, a calcium supplement of 1.2 g/day reduces the incidence of spine fractures and halts measurable bone loss.

Age considerations in nutrient needs for bone health: older adults

Current knowledge of the relation between nutrition and bone health in the elderly is sufficient, if applied, to lead to a reduction in fractures in the aged of from 30-60%. The critical nutrients are calcium and vitamin D, and possibly phosphate as well. Additionally, nutritional measures, especially protein repletion, dramatically improve outcomes from hip fracture. Fortunately the indicated interventions have a favorable cost-benefit relationship, especially when skim milk is used as the source of the needed nutrients.

Pathophysiology of osteoporosis

As with many chronic diseases that express themselves late in life, osteoporosis is distinctly multifactorial both in etiology and in pathophysiology. Osteoporotic fractures occur because of a combination of injury and intrinsic bony fragility. The injury comes most often from a combination of falls, poor postural reflexes that fail to protect bony parts from impact, and reduced soft tissue padding over bony prominences. The bony fragility itself is a composite of geometry, low mass density, severance of microarchitectural connections in trabecular structures, and accumulated fatigue damage. Reduced bone mass, in turn, is caused by varying combinations of gonadal hormone deficiency, inadequate intakes of calcium and vitamin D, decreased physical activity, comorbidity, and the effects of drugs used to treat various unrelated medical conditions. Finally, the often poor outcome from hip fracture in the elderly is partly caused by associated protein-calorie malnutrition. An adequate preventive program for osteoporotic fracture must address as many of these factors as possible, ie, it must be as multifaceted as the disease is multifactorial.

Prevalence and severity of vertebral fracture: the Saunders County Bone Quality Study

Vertebral fracture prevalence and severity were analyzed by sex and age in an age-stratified proportionate sample of the enumerated population of women and men 50 years of age and older in Saunders County, Nebraska. The sample consisted of 899 women and 529 men. Of these, all but 10 women and 2 men had readable lateral spine radiographs. For both sexes, fracture prevalence rises with age. Women in their fifties have 10% vertebral fracture prevalence, and women in their eighties, 45% prevalence. Men in their fifties have 29% prevalence, and men in their eighties, 39% prevalence. The rise in prevalence and total spinal deformity with age is much greater for women than for men, but the prevalence of vertebral deformity in the fifties is much greater in men than in women.

The association of patellar ultrasound transmissions and forearm densitometry with vertebral fracture, number and severity: the Saunders County Bone Quality Study

Ultrasonic measures of bone have been available for clinical research purposes for nearly 10 years, yet there still seems to be a need to compare ultrasound with the accepted gold standard of densitometry. Recently there have been published reports showing that ultrasound measures are associated with both appendicular and hip fracture, in particular after adjustment for densitometry measures. We present here a comparison between speed of sound through the patella and forearm bone densitometry, using their association with prevalent vertebral fractures in a population-based study of women and men. The prospective phase of the Saunders Bone Quality Study includes 1401 women and men who had baseline spine radiographs, patellar ultrasound, and forearm densitometry measurements. Multivariate forward logistic regression was used to determine the age-adjusted odds of vertebral fracture, the number of fractures, and the severity of these fractures, when patellar ultrasound and each of four forearm densitometry measures were entered into the model. Age is the most important factor associated with vertebral fractures, their number, and severity for women, while age is not significantly related to vertebral fractures for men. Of the bone status measures, patellar ultrasound entered the logistic regression models more consistently than any other measure except ulnar bone mineral density for women. The ultrasound measure entered every model for men. We conclude that patellar ultrasound velocity is more consistently associated with the odds of vertebral fractures than radius bone mineral content.

Wheat bran abolishes the inverse relationship between calcium load size and absorption fraction in women

Fractional calcium absorption from varying intakes of calcium carbonate co-ingested with wheat bran, as well as alone, was measured in a randomized crossover study in healthy adult women. The calcium carbonate was intrinsically labeled with 45Ca. Absorption from the carbonate, ingested without bran, showed the expected inverse relationship to the logarithm of ingested load size (slope = -0.1199; not substantially different from the value previously reported for milk). At 0.5 mmol calcium load, fractional absorption averaged 0.769 +/- 0.134, whereas at 12.5 mmol load it averaged 0.378 +/- 0.069. In contrast, fractional absorption from calcium carbonate co-ingested with 40 g of a cereal product containing 16 g wheat bran, across a calcium load range from 0.5 to 15.5 mmol, was essentially constant (mean for all loads: 0.230 +/- 0.069). Thus, the calcium-binding capacity of the bran cereal altered the usual inverse relationship between calcium load and fractional absorption. In vitro calcium binding to the bran cereal was linear over a wide range of calcium levels. This suggests that binding of calcium to one or more components of the bran cereal is sufficient to explain the reduced absorption demonstrated in vivo.

Ultrasound, densitometry, and extraskeletal appendicular fracture risk factors: a cross-sectional report on the Saunders County Bone Quality Study

The Saunders Bone Quality Study was designed to determine the feasibility of ultrasonic bone measurement, at the patella, as a predictor of low-trauma fractures in a rural population-based study. At the first visit of this 4-year longitudinal study, anthropometric and clinical measurements and medical, surgical and fracture histories were obtained for the 1428 participants 9899 women and 529 men). Explored risk factors for low-trauma fractures included age, sex, calcium intake, alcohol and caffeine ingestion, tobacco use, body mass and grip strength, age of menopause, estrogen replacement therapy, propensity to fall, distal radius and ulna bone mineral content, and bone density. Forward multivariate logistic regression analysis showed that lower ultrasound values are more consistently associated with reported low-trauma appendicular fractures than the commonly reported forearm absorptiometry measures of radius mineral content and density. When ultrasound, age, and the extra skeletal risk factors were included in an additional multivariate model, only age and ultrasound were significantly associated with appendicular fracture history in women (P = 0.0003), whereas only ultrasound was associated in the men (P = 0.001). We conclude that ultrasound is a better measure as association with reported low-trauma fractures than the commonly reported forearm SPA measures. Even after adjustment for many of the extra skeletal risk factors, low AVU is highly associated with low-trauma fracture status for both men and women.

Vitamin D receptor gene polymorphism, bone mass, body size, and vitamin D receptor density

We determined vitamin D receptor (VDR) gene alleles (based on the BsmI restriction site polymorphism), duodenal mucosal receptor density, bone mass at spine and total body, and body size in 32 healthy premenopausal females. While we found no relationship between allele and receptor density in duodenal mucosa, bone mineral content (BMC) at both spine and total body was significantly associated with VDR gene alleles. BMC was highest for the bb allele, lowest for BB, and intermediate for Bb. A similar association was noted between allele and body size variables, particularly weight. When BMC was adjusted for body weight, the association with VDR polymorphism disappeared. The VDR gene polymorphism may be affecting bone mass not through classical nutritional mechanisms (e.g., intestinal calcium absorption), but through an influence on body size.

Patellar ultrasound transmission velocity in healthy children and adolescents

Apparent velocity of ultrasound (AVU) (Signet, Osteo-Technology Cambridge, MA) at the patella was measured on 568 children and adolescents, aged 8 to 18 years. Trend analysis revealed a significant trend (p < 0.004) toward increasing AVU with increasing age and increasing Tanner stage. Height and weight were positively correlated with AVU in both sexes, while dietary intake of calories, protein, and calcium were positively correlated with AVU in males, but not in females. Multiple linear regression revealed that 29% of the variance of AVU in females was described by Tanner stage (p < 0.002) and height (p < 0.007). The best regression model for males accounted for 48% of the variance in AVU and included age (p < 0.0001) and protein intake (p < 0.01). Bone quality has a distribution in children which is similar to the distribution of bone mass and density. Our patellar AVU values can be used as a baseline for much-needed prospective research with children and adolescents.

Ultrasound velocity, through bone predicts incident vertebral deformity

We followed 130 postmenopausal women without evidence of vertebral deformity by lateral spine radiographs on entry into study for 2 years, and repeat spine radiographs were taken at the end of that time. Incident deformities occurring within this 2 year period were detected by two methods, a level-specific radiogrammetric approach and visual inspection by skilled clinicians. Fourteen incident deformities were detected by the radiogrammetric method, and 19 by the clinicians. Ultrasound transmission velocity was measured at the patella in each subject on entry. Values for ultrasound velocity were significantly correlated with incident fracture occurrence, with individuals having velocity values more than one standard deviation below the mean for the group exhibiting from 3.3 to 4.6 times the probability of incident fracture as individuals with velocity values more than one standard deviation above the mean. Thus, low values for ultrasound transmission velocity at the patella detect yet-unexpressed bony fragility at the spine and predict future fracture.

Caffeine and the calcium economy revisited

We report an analysis of data from 560 calcium balance studies carried out on 190 women aged 34.8-69.3 years at the time of study. The main purposes were to confirm a previously observed association between caffeine intake and calcium balance, and to attribute the association, if possible, to specific component(s) of balance. We found a caffeine relationship such that for every 6 fl oz (177.5 ml) serving of caffeine-containing coffee, calcium balance was more negative by 0.114 mmol/day (4.6 mg/day) (P < 0.001). The relationship was localized to the input side of the balance equation, and both of its components (i.e. calcium intake and calcium absorption efficiency) were independently and inversely associated with caffeine intake. There was no evidence that the putative caffeine effect is confined to, or is greater among, subjects with low calcium intakes or those who are older or estrogen-deprived. The magnitude of the negative effect of caffeine on calcium balance suggests that it can be offset by increasing calcium intake by about 1 mmol (40 mg) for every 177.5 ml serving of caffeine-containing coffee.

Effect of psyllium on absorption of co-ingested calcium

OBJECTIVE

To determine whether psyllium fiber (in the form of Metamucil) interferes with absorption of calcium ingested at the same meal.

DESIGN

Three-way, randomized, cross-over study in 15 healthy postmenopausal women, with calcium-fortified orange juice as the calcium source in all three meals. The test load of calcium was 219 mg (approximately 5.5 mmol). One test meal contained Metamucil, providing 3.4 g psyllium fiber; one had an equivalent amount of neutral cellulose; the third had no added fiber.

METHODS

The calcium-fortified orange juice was extrinsically labeled with 45Ca; calcium absorption fraction was calculated from the specific radioactivity of serum calcium at 5 hours after tracer ingestion.

RESULTS

Fractional absorption of calcium from orange juice without added fiber averaged 0.341 +/- 0.059; in the presence of psyllium fiber, 0.317 +/- 0.067; and in the presence of neutral fiber, 0.354 +/- 0.083. While the absorption with cellulose was slightly higher than in the absence of fiber, and the absorption with psyllium was slightly lower, neither difference was statistically significant. However, the difference between added psyllium and cellulose was statistically significant (P < .05).

CONCLUSION

Psyllium in the form of Metamucil makes little practical difference to availability of co-ingested calcium when ingested at typical therapeutic doses.

Comparison of speed of sound ultrasound with single photon absorptiometry for determining fracture odds ratios

The purpose of this study was to compare the ability of ultrasound velocity measurement with that of single photon absorptiometry to determine the odds of history of fracture since age 40, for a population-based study. To do this we computed odds ratios and 95% confidence intervals for 809 women and 502 men, aged 50 years and older, who are participants in the prospective phase of the Saunders County Bone Quality Study. These participants received both the ultrasound and single photon absorptiometry bone measurements at the initiation of the study. In addition, a history of all fractures that had occurred to participants since age 40 was obtained. The two bone assessment methods were compared by examining the magnitude of the odds ratios, to determine which produces the highest estimate of the probability of odds of fracture, and by examining widths of the respective confidence intervals to show which estimate of odds ratio is the most precise. Ultrasound velocity estimates a higher probability of odds of both low-trauma fractures and all fractures than distal radius and ulna bone mineral content, but lower than bone mineral density at the same sites for both women and men. However, the ultrasound measure is more precise than bone mineral density, but less precise than bone mineral content. We conclude that ultrasound velocity is as good as single photon absorptiometry in estimating odds of fracture.

An investigation of sources of variation in calcium absorption efficiency

To examine putative sources of interindividual variation in calcium absorption efficiency, we studied 41 healthy premenopausal women (mean age, 36.4 yr). About half were randomized to pretreatment with supplemental 25-hydroxyvitamin D (25OHD; 20 micrograms/day [corrected] for approximately 34 days) before testing. We measured dietary factors, humoral regulators, intestinal motility, mucosal histology, mucosal vitamin D receptor levels, and calcium absorption efficiency. In winter tests, but not in summer tests, calcium absorption fraction was significantly higher in the pretreated group (mean, 0.465 vs. 0.387). Serum 25OHD, intestinal transit, and urinary calcium to creatinine ratio were all significantly and positively correlated to calcium absorption efficiency. However, neither the level of 1,25-dihydroxyvitamin D receptors in duodenal mucosa nor circulating 1,25-dihydroxyvitamin D was related to calcium absorption efficiency. These findings, which are consistent with other published human data, suggest that 25OHD plays a more prominent role in the regulation of calcium absorption than is generally believed. In a multiple regression model, serum 25OHD, mouth to cecum transit time, and fasting urinary calcium/creatinine ratio explained 44% of the observed variation in calcium absorption efficiency.

Cortical ultrasound velocity as an indicator of bone status

Normative population data are reported here for velocity of ultrasound in tibial cortical bone in a population-based sample of both men and women (n = 371). The cortical measurement is highly precise with reproducibility of the order of 0.5%. As with heel and patellar trabecular velocity, tibial cortical velocity declines with age from the fourth through the ninth decades. The rate is 1.7 m/s per year in men and 4.1 m/s per year in women. Tibial cortical velocity values correlate with patellar velocity and with forearm mineral, with correlation coefficients ranging from + 0.46 to + 0.54 in women and + 0.27 to + 0.43 in men (P < 0.002 for all). Tibial velocity averaged 77-104 m/s lower (2-3%: equal to about 1 SD of the young adult normal distribution) in individuals with a history of low-energy appendicular fractures (P < 0.05), and the difference remained significant after adjusting for age. However, there were no perceptible differences in tibial velocity for those with and without vertebral fractures. Odds ratios derived from logistic regression showed an approximate twofold increase in likelihood of low-energy appendicular fracture for every standard deviation decrement in velocity. Comparison of tibial velocity with patellar velocity and forearm density in the same individuals revealed tibial velocity to be more strongly associated with appendicular fractures than patellar velocity for women and about the same for men, and less strongly associated than patellar velocity for vertebral fractures. We conclude that tibial cortical velocity provides useful information about bone status in populations at risk for osteoporosis, and seems particularly well suited for assessing appendicular fracture risk.