Reduced kidney function is associated with BMD, bone loss and markers of mineral homeostasis in older women: a 10-year longitudinal study

Kidney function decreases with age; however, the long-term influence on bone density (BMD) in older women already at risk of osteoporosis is unknown. We followed kidney function and bone loss for 10 years. Declining kidney function was adversely associated with bone loss and mineral homeostasis in old women, though it attenuated with advanced aging.

INTRODUCTION

Existing studies do not fully address the relationship between kidney function and bone metabolism with advanced aging in Caucasian women. This study describes the association between kidney function, BMD, bone loss and bone metabolism in older women and provides a review of the available literature for context.

METHODS

We studied participants from the OPRA cohort with follow-up after 5 and 10 years. Using plasma cystatin C (cysC), estimated glomerular function rate (eGFR) was evaluated at age 75 (n = 981), 80 (n = 685) and 85 (n = 365). Women were stratified into "normal" function (CKD stages 1-2), "intermediate" (stage 3a) and "poor" (stages 3b-5), and outcome measures-BMD, bone loss and markers of mineral homeostasis-were compared.

RESULTS

Femoral neck (FN) BMD positively associated with kidney function at 75 years old ([Formula: see text] = 0.001, p = 0.028) and 80 years old ([Formula: see text] = 0.001, p = 0.001), although with small effect size. Prevalence of osteoporosis (FN T-score ≤ - 2.5) did not differ with kidney function. Measured at age 75, women with poor kidney function had higher annual percentage bone loss over 5 years compared to those with normal function (2.3%, 95% CI 1.8-2.8 versus 1.3%, 95% CI 1.1-1.5, p = 0.007), although not when measured from age 80 or 85. Additionally, markers of mineral homeostasis (PTH, phosphate, vitamin D, calcium), CRP and osteocalcin differed by kidney function.

CONCLUSIONS

In old women, kidney function is associated with BMD, bone loss and altered mineral homeostasis; probably, a relationship attenuated in the very elderly.

C-reactive protein, bone loss, fracture, and mortality in elderly women: a longitudinal study in the OPRA cohort

SUMMARY

This longitudinal study investigates the association between C-reactive protein (CRP), osteoporosis, fractures, and mortality in 1044 elderly women. CRP was not an indicator for low bone mineral density (BMD), bone loss, or fracture in elderly women; however, women with elevated CRP levels over a prolonged period lost more bone over the 10-year follow-up, although fracture risk was not increased.

INTRODUCTION

Inflammation may contribute to the pathophysiology underlying impaired bone metabolism. This study investigates the association between CRP, BMD, bone loss, fracture risk, and mortality in women aged 75 and above.

METHODS

This longitudinal study is based on 1044 women, all age 75 at inclusion, reassessed at ages 80 and 85, with a mean follow-up time of 11.6 years (maximum 16.9 years).

RESULTS

Women in the lowest CRP quartile (mean 0.63 mg/L) had lower BMD compared to those in the highest CRP quartile (mean 5.74 mg/L) at total hip (TH) (0.809 vs. 0.871 g/cm2, p<0.001) and femoral neck (FN) (0.737 vs. 0.778 g/cm2, p=0.007). A single measurement of CRP was not associated with bone loss; however, women with persistently elevated CRP, i.e., ≥3 mg/L at ages 75 and 80 had significantly higher bone loss compared to women with CRP<3 mg/L (TH -0.125 vs. -0.085 g/cm2, p=0.018 and FN -0.127 vs. -0.078 g/cm2, p=0.005) during 10 years of follow-up. Women in the highest CRP quartile had a lower risk of osteoporotic fractures (hazard ratios (HR) 0.76 (95% confidence intervals (CI) 0.52-0.98)) compared to those in the lowest, even after adjusting for weight and BMD. Mortality risk was only increased among women with the highest CRP levels.

CONCLUSION

CRP was not an indicator for low BMD, bone loss, or fracture in elderly women in this study. Persistently elevated CRP however seemed to be detrimental to bone health and may be associated with a higher rate of bone loss. Only the highest CRP levels were associated with mortality.

Vitamin D insufficiency over 5 years is associated with increased fracture risk-an observational cohort study of elderly women

This study of elderly Swedish women investigated the association between chronic vitamin D insufficiency and osteoporotic fractures occurring between ages 80-90. The incidence and risk of hip and major osteoporotic fractures was significantly higher in elderly women with low vitamin D levels maintained over 5 years.

INTRODUCTION

Vitamin D insufficiency among the elderly is common; however, relatively little is known about the effects of long-term hypovitaminosis D on fracture. We investigated sequential assessment of serum 25(OH)D at age 75 and 80 to determine if continuously low 25(OH)D levels are associated with increased 10-year fracture incidence.

METHODS

One thousand forty-four Swedish women from the population-based OPRA cohort, all 75 years old, attended at baseline (BL); 715 attended at 5 years. S-25(OH)D was available in 987 and 640, respectively and categorized as: <50 (Low), 50-75 (Intermediate), and >75 nmol/L (High). Incident fracture data was collected with maximum follow-up to 90 years of age.

RESULTS

Hip fracture incidence between age 80-85 was higher in women who had low 25(OH)D at both baseline and 5 years (22.2 % (Low) vs. 6.6 % (High); p = 0.003). Between age 80-90, hip fracture incidence was more than double that of women in the high category (27.9 vs. 12.3 %; p = 0.006). Within 5-years, 50 % of women in the continuously low group compared to 34 % in the continuously high 25(OH)D group had an osteoporotic fracture (p = 0.004) while 10-year incidence was higher compared to the intermediate (p = 0.020) but not the high category (p = 0.053). The 10-year relative risk of hip fracture was almost three times higher and osteoporotic fracture risk almost doubled for women in the lowest 25(OH)D category compared to the high category (HR 2.7 and 1.7; p = 0.003 and 0.023, respectively).

CONCLUSION

In these elderly women, 25(OH)D insufficiency over 5-years was associated with increased 10-year risk of hip and major osteoporotic fractures.

Birth weight is more important for peak bone mineral content than for bone density: the PEAK-25 study of 1,061 young adult women

Lower birth weight has a negative association with adult BMC and body composition in young adult Swedish women.

INTRODUCTION

The aim of this study was to evaluate the influence of birth weight on peak bone mass and body composition in a cohort of 25-year-old women.

METHODS

One thousand sixty-one women participated in this cross-sectional population-based study using dual energy X-ray absorptiometry (DXA) to assess bone mineral content (BMC), bone mineral density (BMD), and body composition (total body (TB), femoral neck (FN), total hip (TH), lumbar spine L1-L4 (LS), and lean and fat mass). Birth weight data was available for 1,047 women and was categorized into tertiles of low (≤3,180 g), intermediate (3,181-3,620 g), and high (≥3,621 g) birth weight.

RESULTS

Significant correlations were observed between birth weight and TB-BMC (r=0.159, p<0.001), FN-BMC (r=0.096, p<0.001), TH-BMC (r=0.102, p=0.001), LS-BMC (r=0.095, p=0.002), and lean mass (r=0.215, p<0.001). No correlation was observed between birth weight and BMD. The estimated magnitude of effect was equivalent to a 0.3-0.5 SD difference in BMC for every 1 kg difference in birth weight (151 g (TB); 0.22 g (FN); 1.5 g (TH), 2.5 kg TB lean mass). The strongest correlations between birth weight and BMC occurred in women with lowest birth weights, although excluding women who weighed<2,500 g at birth, and the correlation remained significant although slightly weaker.

CONCLUSIONS

Women with lower birth weight have lower BMC and less lean and fat mass at the age of 25, independent of current body weight. Lower birth weight has a greater negative influence on bone mass than the positive influence of higher birth weight.

Degenerative changes at the lumbar spine--implications for bone mineral density measurement in elderly women

Degenerative changes of the lumbar spine may lead to misinterpretation of bone mineral density (BMD) measurements and cause underdiagnosis of osteoporosis. This longitudinal study of 1,044 women, 75 years at inclusion and followed for 10 years, shows that identification of apparent degenerative changes on the dual energy X-ray absorptiometry (DXA) scan can increase the proportion diagnosed.

INTRODUCTION

In the elderly, degenerative manifestations in the lumbar spine may result in falsely elevated BMD values, consequently missing a large proportion of those with osteoporosis. Our aim was to determine the distribution and impact of degenerative changes on lumbar spine DXA over time and its clinical implications.

METHODS

Participants were 1,044 women from the population-based Osteoporosis Risk Assessment cohort. All women were 75 years old at invitation and followed up after 5 years (n=715) and 10 years (n=382). Degenerative changes were evaluated visually on the DXA image for each vertebra L1 to L4 (intraobserver precision kappa values of 0.66-0.70).

RESULTS

At baseline, apparent degenerative changes were more frequent in the inferior segments of the lumbar spine [5% (L1), 15% (L2), 26% (L3), and 36% (L4)] and increased over time. At 10 years, the prevalences were 20% (L1), 39% (L2), 59% (L3), 72% (L4), resulting in a significant increase in overall BMD. In women without apparent degenerative changes, BMD remained stable between 75 and 85 rather than an expected bone loss. At baseline, 37% had osteoporosis (BMD<-2.5) at L1-L4; exclusion of women with apparent degenerative changes increased this proportion to 47%. Using L1-L2, which was less prone to degenerative changes, 46% of women were classified as osteoporotic regardless of degenerative changes.

CONCLUSION

Degenerative changes were very common in elderly women, accelerated disproportionately over time, were increasingly frequent from vertebrae L1 to L4, and had significant impact on diagnosing osteoporosis. This suggests that routine reporting of spine BMD at L1-L2 would add valuable information for reassessment and monitoring.

Self-reported recreational exercise combining regularity and impact is necessary to maximize bone mineral density in young adult women: a population-based study of 1,061 women 25 years of age

Recreational physical activity in 25-year-old women in Sweden increases bone mineral density (BMD) in the trochanter by 5.5% when combining regularity and impact. Jogging and spinning were especially beneficial for hip BMD (6.4-8.5%). Women who enjoyed physical education in school maintained their higher activity level at age 25.

INTRODUCTION

The aims of this study were to evaluate the effects of recreational exercise on BMD and describe how exercise patterns change with time in a normal population of young adult women.

METHODS

In a population-based study of 1,061 women, age 25 (±0.2), BMD was measured at total body (TB-BMD), femoral neck (FN-BMD), trochanter (TR-BMD), and spine (LS-BMD). Self-reported physical activity status was assessed by questionnaire. Regularity of exercise was expressed as recreational activity level (RAL) and impact load as peak strain score (PSS). A permutation (COMB-RP) was used to evaluate combined endurance and impacts on bone mass.

RESULTS

More than half of the women reported exercising on a regular basis and the most common activities were running, strength training, aerobics, and spinning. Seventy percent participated in at least one activity during the year. Women with high RAL or PSS had higher BMD in the hip (2.6-3.5%) and spine (1.5-2.1%), with the greatest differences resulting from PSS (p < 0.001-0.02). Combined regularity and impact (high-COMB-RP) conferred the greatest gains in BMD (FN 4.7%, TR 5.5%, LS 3.1%; p < 0.001) despite concomitant lower body weight. Jogging and spinning were particularly beneficial for hip BMD (+6.4-8.5%). Women with high-COMB-RP scores enjoyed physical education in school more and maintained higher activity levels throughout compared to those with low scores.

CONCLUSION

Self-reported recreational levels of physical activity positively influence BMD in young adult women but to maximize BMD gains, regular, high-impact exercise is required. Enjoyment of exercise contributes to regularity of exercising which has short- and long-term implications for bone health.

Association between vitamin D receptor gene polymorphisms, falls, balance and muscle power: results from two independent studies (APOSS and OPUS)

SUMMARY

Fall prevention is a key strategy for reducing osteoporotic fractures. We investigated the association between vitamin D receptor (VDR) polymorphisms and reported falls in postmenopausal women. Bsm1 polymorphisms were associated with falls, balance and muscle power measurements. These results may explain some of the excess fracture risk associated with VDR in some studies.

INTRODUCTION

Fall prevention is a key strategy for reducing osteoporotic fractures. It has been suggested that vitamin D supplementation may reduce the incidence of falls by reducing body sway and increasing muscle power. The vitamin D receptor gene is a well-studied candidate gene for osteoporosis. We investigated the association between VDR polymorphisms and reported falls in postmenopausal women.

METHODS

Falls data were collected in two separate population cohorts. Five polymorphisms of the VDR gene were analysed (Cdx-2, Fok-1, BsmI, Taq1 and Apa1) in the Aberdeen Prospective Osteoporosis Screening Study (APOSS) cohort. Results found in APOSS were then validated in an independent cohort--the Osteoporosis and Ultrasound (OPUS) study (Bsm1 and Fok1 only), where muscle power and balance were also measured.

RESULTS

Carriers of the 'B' allele (Bsm1) showed an increased risk for falls. In APOSS, this was statistically significant for visit 3 multiple falls (p = 0.047) and for recurrent falls (p = 0.043). Similar results were found in OPUS for visit 1 falls (p = 0.025) and visit 1 multiple falls (p = 0.015). Bsm1 polymorphisms were also associated with balance and muscle power measurements.

CONCLUSIONS

In conclusion, these results demonstrate an association between the Bsm1 polymorphism and risk of falling that may explain some of the excess fracture risk associated with VDR in some studies.

Genetic variation in the PTH pathway and bone phenotypes in elderly women: evaluation of PTH, PTHLH, PTHR1 and PTHR2 genes

INTRODUCTION

Parathyroid hormone (PTH) is a key regulator of calcium metabolism. Parathyroid hormone-like hormone (PTHrP) contributes to skeletal development through regulation of chondrocyte proliferation and differentiation during early bone growth. Both PTH and PTHrP act through the same receptor (PTHR1). A second receptor, PTHR2, has been identified although its function is comparatively unknown. PTH hyper-secretion induces bone resorption, whereas intermittent injection of PTH increases bone mass. To explore the effects of genetic variation in the PTH pathway, we have analysed variations in PTH, PTHLH, PTHR1 and PTHR2 in relation to bone mass and fracture incidence in elderly women.

MATERIALS AND METHODS

This study includes 1044 elderly women, all 75 years old, from the Malmö Osteoporosis Prospective Risk Assessment study (OPRA). Single nucleotide polymorphisms (SNPs) from 4 genes and derived haplotypes in the PTH signaling pathway were analysed in 745-1005 women; 6 SNPs in the PTH gene and 3 SNPs each in the PTHLH, PTHR1 and PTHR2 genes were investigated in relation to BMD (assessed at baseline), fracture (434 prevalent fractures of all types over lifetime, self-reported and 174 incident fractures up to 7 years, X-ray verified) and serum PTH.

RESULTS AND CONCLUSION

Individually, SNPs in the 4 loci did not show any significant association with BMD. Neither were PTHLH, PTHR1 and PTHR2 polymorphisms associated with fracture. Three of 5 common haplotypes, accounting for >98% of alleles at the PTH locus, were identified as independent predictors of fracture. Haplotype 9 (19%) was suggestive of an association with fractures of any type sustained during lifetime (p=0.018), with carriers of one or more copies of the haplotype having the lowest incidence (p=0.006). Haplotypes 1 (13%) and 5 (37%) and 9 were suggestive of an association with fractures sustained between 50 and 75 years (p=0.02, p=0.013 and p=0.034). Carriers of haplotypes 1 and 5 were more likely to suffer a fracture (haplotype 1, p=0.045; haplotype 5, p=0.008). We conclude, that while further genotyping across the gene is recommended, in this cohort of elderly Swedish women, polymorphisms in PTH may contribute to the risk of fracture through mechanisms that are independent of BMD.

Polymorphisms of the interleukin-6 gene are associated with bone mineral density

Genetic factors play an important role in determining bone mass and several genes probably act as regulators of this process. Interleukin-6 (IL-6) is a candidate gene for regulation of bone density, since it has stimulatory effects on cells of the osteoclast lineage and has been implicated in the pathogenesis of bone loss associated with estrogen deficiency. Here we studied the relationship between bone mineral density (BMD) and a polymorphic AT rich minisatellite repeat in the 3' flank of the IL-6 gene in a cohort of 200 women. Six length variants were identified (designated A-F), but four of these were rare such that the last majority of individuals fell into one of two common genotypes: F/F (58.5%) and C/F (27.5%). There was a significant relationship between IL-6 genotype and bone mass at the lumbar spine as determined by analysis of variance (p = 0.04) and a similar trend for bone mass at the femoral neck (p = 0.11). When BMD values were compared in the two common genotypes, we found that spine BMD values were significantly higher in the C/F genotype (mean +/- SEM = 0.94 +/- 0.04 g/cm2) as compared with the F/F genotype (0.81 +/- g/cm2; p = 0.012). A similar trend was seen for hip BMD values, but here, the difference failed to reach statistical significance (p = 0.06). Further analysis showed that genotype-specific effects on bone mass were observed in both premenopausal and postmenopausal women and did not increase with age, suggesting that the association between IL-6 polymorphisms and bone density may be mediated by an effect on peak bone mass, rather than rate of bone loss. We conclude that bone mass is associated with two common polymorphisms of the IL-6 gene. Although the mechanisms that underlie this association will require further research, our data suggest that polymorphic variation at the IL-6 gene locus may contribute to the genetic regulation of bone mass.

Nitric oxide mediates suppression of T cell responses in murine Trypanosoma brucei infection

African trypanosomes induce a generalized state of immunosuppression in their mammalian hosts. One characteristic of this is a suppression of lymphocyte responses to mitogen, which is mediated by suppressor macrophages. We investigated the involvement of nitric oxide in this phenomenon. Both peritoneal and splenic cell cultures from infected mice released nitrite and this was inhibitable by NG-monomethyl L-arginine (L-NMMA). The release of nitrite correlated with suppressed splenic T cell proliferative responses to concanavalin A. It was shown that adherent spleen cells from infected mice mediate suppression, which could be abrogated by L-NMMA. These results suggest that in T. brucei infection, the activation of macrophages to produce nitric oxide leads to impaired lymphocyte responses and immunosuppression.