Background

Moderate kidney disease may predispose to infection. We sought to determine whether decreased kidney function, as estimated by serum cystatin C, was associated with the risk of infection-related hospitalization in older individuals.

Study Design

Cohort Study.

Setting & Participants

5,142 Cardiovascular Health Study participants with measured serum creatinine and cystatin C and without eGFR <15 ml/min/1.73 m2 at enrollment.

Predictor

The primary exposure of interest was estimated glomerular filtration rate using serum cystatin C (eGFRSCysC).

Outcome

Infection-related hospitalizations during a median follow-up of 11.5 years.

Results

In adjusted analyses, eGFRSCysC categories of 60–89, 45–59, and 15–44 ml/min/1.73 m2 were associated with 16%, 37%, and 64% greater risk of all-cause infection-related hospitalization, respectively, compared with an eGFRSCysC ≥90 ml/min/1.73 m2. When cause specific infection was examined, an eGFRSCysC of 15–44 ml/min/1.73 m2 was associated with an 80% greater risk of pulmonary and 160% greater risk of genitourinary infection compared with an eGFRSCysC ≥90 ml/min/1.73 m2.

Limitations

No measures of urinary protein, study limited to principal discharge diagnosis.

Conclusions

Lower kidney function, estimated using cystatin C, was associated with a linear and graded risk of infection-related hospitalization. These findings highlight that even moderate degrees of reduced kidney function are associated with clinically significant higher risks of serious infection in older individuals.

Chronic kidney disease is characterized, in part, as a state of decreased production of 1,25-dihydroxyvitamin D (1,25(OH)2D); however, this paradigm overlooks the role of vitamin D catabolism. We developed a mass spectrometric assay to quantify serum concentration of 24,25-dihydroxyvitamin D (24,25(OH)2D), the first metabolic product of 25-hydroxyvitamin D (25(OH)D) by CYP24A1, and determined its clinical correlates and associated outcomes among 278 participants with chronic kidney disease in the Seattle Kidney Study. For eGFRs of 60 or more, 45–59, 30–44, 15–29, and under 15 ml/min/1.73m2, the mean serum 24,25(OH)2D concentrations significantly trended lower from 3.6, 3.2, 2.6, 2.6, to 1.7 ng/ml, respectively. Non-Hispanic Black race, diabetes, albuminuria, and lower serum bicarbonate were also independently and significantly associated with lower 24,25(OH)2D concentrations. The 24,25(OH)2D concentration was more strongly correlated with that of parathyroid hormone than was 25(OH)D or 1,25(OH)2D. A 24,25(OH)2D concentration below the median was associated with increased risk of mortality in unadjusted analysis, but this was attenuated with adjustment for potential confounding variables. Thus, chronic kidney disease is a state of stagnant vitamin D metabolism characterized by decreases in both 1,25(OH)2D production and vitamin D catabolism.

Low circulating concentrations of 25-hydroxyvitamin D (25(OH)D) are associated with adverse health outcomes in diverse populations. However, 25(OH)D concentrations vary seasonally with varying exposure to sunlight, so single measurements may poorly reflect long-term 25(OH)D exposure. The authors investigated cyclical trends in average serum 25(OH)D concentrations among 2,298 individuals enrolled in the Cardiovascular Health Study of community-based older adults (1992–1993). A sinusoidal model closely approximated observed 25(OH)D concentrations and fit the data significantly better than did a mean model (P < 0.0001). The mean annual 25(OH)D concentration was 25.1 ng/mL (95% confidence interval: 24.7, 25.5), and the mean peak-trough difference was 9.6 ng/mL (95% confidence interval: 8.5, 10.7). Male sex, higher latitude of study site, and greater physical activity levels were associated with larger peak-trough difference in 25(OH)D concentration (each P < 0.05). Serum concentrations of intact parathyroid hormone and bone-specific alkaline phosphatase also varied in a sinusoidal fashion (P < 0.0001), inversely to 25(OH)D. In conclusion, serum 25(OH)D varies in a sinusoidal manner, with large seasonal differences relative to mean concentration and laboratory evidence of biologic sequelae. Single 25(OH)D measurements might not capture overall vitamin D status, and the extent of misclassification could vary by demographic and behavioral factors. Accounting for collection time may reduce bias in research studies and improve decision-making in clinical care.

Background: Whether lipoprotein-associated phospholipase A2 (Lp-PLA2) levels are associated with kidney function decline has not been well studied. Methods: We investigated associations of Lp-PLA2 antigen and activity with kidney function decline and rapid decline over 5.7 years in the Cardiovascular Health Study (n = 4,359). We estimated kidney function by cystatin C (eGFRcys) in repeated measures, and defined rapid decline as ≥3 ml/min/1.73 m2 per year. We stratified by baseline preserved GFR (≥60 ml/min/1.73 m2). Results: Mean age was 72 ± 5 years. Average eGFRcys decline was −1.79 ml/min/1.73 m2 (SD = 2.60) per year. Among persons with preserved GFR, compared to the lowest quartile of Lp-PLA2 antigen, eGFRcys decline was faster among persons in the second, β −0.31 (95% CI −0.52, −0.10), third −0.19 (–0.41, 0.02) and fourth quartiles −0.26 (–0.48, −0.04) after full adjustment. Persons in the highest quartile of Lp-PLA2 antigen had increased odds of rapid decline 1.34 (1.03, 1.75), compared to the lowest. There was no significant association between levels of Lp-PLA2 activity and eGFRcys decline or rapid decline. Associations were not statistically significant among persons with low eGFR (<60 ml/min/1.73 m2) at baseline. Conclusion: Higher levels of Lp-PLA2 antigen but not activity were significantly associated with faster rates of kidney function decline. These findings may suggest a novel vascular pathway for kidney disease progression.

Recent studies have demonstrated greater risks of cardiovascular events and mortality among persons who have lower 25-hydroxyvitamin D (25-OHD) and higher parathyroid hormone (PTH) levels. We sought to evaluate the association between markers of mineral metabolism and sudden cardiac death (SCD) among the 2,312 participants from the Cardiovascular Health Study who were free of clinical cardiovascular disease at baseline. We estimated associations of baseline 25-OHD and PTH concentrations individually and in combination with SCD using Cox proportional hazards models after adjustment for demographics, cardiovascular risk factors, and kidney function. During a median follow-up of 14 years, there were 73 adjudicated SCD events. The annual incidence of SCD was greater among subjects who had lower 25-OHD concentrations: 2 events per 10,000 for 25-OHD ≥ 20 ng/ml and 4 events per 10,000 for 25-OHD < 20 ng/ml. Similarly, SCD incidence was greater among subjects who had higher PTH concentrations: 2 events per 10,000 for PTH ≤ 65 pg/ml and 4 events per 10,000 for PTH > 65 pg/ml. Multivariate adjustment attenuated associations of 25-OHD and PTH with SCD. Finally, 267 participants (11.7% of the cohort) had high PTH and low 25-OHD concentrations. This combination was associated with a more than 2-fold risk of SCD after adjustment (hazard ratio 2.19, 95% confidence interval 1.17, 4.10, p=0.017) compared to participants with normal levels of PTH and 25-OHD. The combination of lower 25-OHD and higher PTH concentrations appears to be associated independently with SCD risk among older adults without cardiovascular disease.

Background

Vitamin D deficiency and parathyroid hormone (PTH) excess are common among older adults and may adversely impact cardiovascular health. We evaluated associations of 25-hydroxyvitamin D (25-OHD) and PTH concentrations, separately, and in combination, with incident cardiovascular events and mortality during 14 years of follow-up in the Cardiovascular Health Study.

Methods and results

We studied 2,312 participants who were free of cardiovascular disease at baseline. We measured 25-OHD and intact PTH from previously frozen serum using mass spectrometry and a two-site immunoassay. Outcomes were adjudicated cases of myocardial infarction, heart failure, cardiovascular death, and all cause mortality. There were 384 participants (17%) who had serum 25-OHD concentrations <15 ng/ml and 570 (25%) who had serum PTH concentrations ≥ 65 pg/ml. After adjustment, each 10-ng/ml lower 25-OHD concentration was associated with a 9% greater (95% CI 2% to 17% greater) relative hazard of mortality and a 25% greater (95% CI 8% to 44% greater) relative hazard of myocardial infarction. Serum 25-OHD concentrations <15 ng/ml, were associated with a 29% greater (95% CI 5% to 55% greater) risk of mortality. Serum PTH concentrations ≥ 65 pg/ml were associated with a 30% greater risk of heart failure (95% CI 6% to 61% greater), but not other outcomes. There was no evidence of an interaction between serum 25-OHD and PTH concentrations and cardiovascular events.

Conclusions

Among older adults, 25-OHD deficiency is associated with myocardial infarction and mortality; PTH excess is associated with heart failure. Vitamin D and PTH might influence cardiovascular risk through divergent pathways.

Objectives

To evaluate mineral metabolism markers as potential risk factors for calcific aortic valve disease.

Background

Mineral metabolism disturbances are common among older people and may contribute to cardiac valvular calcification. Associations of serum mineral metabolism markers with cardiac valvular calcification have not been evaluated in a well-characterized general population of older adults.

Methods

We measured serum levels of phosphate, calcium, parathyroid hormone, and 25-hydroxyvitamin D in 1,938 Cardiovascular Health Study participants who were free of clinical cardiovascular disease and who underwent echocardiography measurements of aortic valve sclerosis (AVS), mitral annular calcification (MAC), and aortic annular calcification (AAC). We used logistic regression models to estimate associations of mineral metabolism markers with AVS, MAC, and AAC after adjustment for relevant confounding variables, including kidney function.

Results

The respective prevalences of AVS, MAC, and AAC were 54%, 39%, and 44%. Each 0.5 mg/dl higher serum phosphate concentration was associated with a greater adjusted odds of AVS (odds ratio 1.17, 95% confidence interval 1.04 to 1.31, p = 0.01), MAC (odds ratio 1.12, 95% confidence interval 1.00 to 1.26, p =0.05), and AAC (odds ratio 1.12, 95% confidence interval 0.99 to 1.25, p = 0.05). In contrast, serum calcium, parathyroid hormone, and 25-hydroxyvitamin D concentrations were not associated with aortic or mitral calcification.

Conclusions

Higher serum phosphate levels within the normal range are associated with valvular and annular calcification in a community-based cohort of older adults. Phosphate may be a novel risk factor for calcific aortic valve disease and warrants further study.

Background

The growing burden and morbidity of chronic kidney disease (CKD) warrant effective strategies for identifying those at increased risk. We examined the association of cystatin C and albuminuria with development of CKD stage 3.

Study Design

Prospective observational study.

Setting and Participants

5,422 participants from the Multi-Ethnic Study of Atherosclerosis with estimated glomerular filtration rate (eGFR) ≥ 60 ml/min/1.73m2.

Predictor

Participants were categorized into four mutually exclusive groups: presence or absence of microalbuminuria (albumin-creatinine ratio >17 and > 25 µg/mg in men and women, respectively) in those with or without cystatin C ≥ 1.0 mg/L.

Outcomes and Measurements

Incident CKD stage 3 was defined as eGFR < 60 ml/min/1.73m2 at the 3rd or 4th visit and an annual decline of > 1 ml/min/1.73 m2. Poisson regression was used to evaluate incident rate ratios in unadjusted and adjusted analyses that include baseline eGFR.

Results

Mean age was 61 years, 49% were men, 38% white, 11% had diabetes, 13.7% had cystatin C ≥ 1mg/L, 8.4% had microalbuminuria, and 2.7 % had cystatin C ≥ 1 mg/L with microalbuminuria. 554 (10%) participants developed CKD stage 3 over a median follow-up of 4.7 years and the adjusted incidence rate ratios (95% CI) were 1.57 (1.19–2.07), 1.37 (1.13–1.66), and 2.12 (1.61–2.80) in those with microalbuminuria, cystatin C ≥ 1 mg/L, and both, respectively, compared to those with neither.

Limitations

Relatively short follow up and absence of measured GFR.

Conclusions

Cystatin C and microalbuminuria are independent risk factors for incident CKD stage 3 and could be useful as screening tools to identify those at increased risk.

Diabetes mellitus and hypertension commonly coexist, but the nature of this link is not well understood. The authors tested whether diabetes and higher concentrations of fasting serum glucose and insulin are associated with increased risk of developing incident hypertension in the community-based Multi-Ethnic Study of Atherosclerosis. At baseline, 3,513 participants were free of hypertension, defined as systolic blood pressure ≥140 mm Hg, diastolic blood pressure ≥90 mm Hg, or use of antihypertensive medications to treat high blood pressure. Of these, 965 participants (27%) developed incident hypertension over 4.7 years’ median follow-up between 2002 and 2007. Compared with participants with normal baseline fasting glucose, those with impaired fasting glucose and diabetes had adjusted relative risks of hypertension of 1.16 (95% confidence interval (CI): 0.96, 1.40) and 1.41 (95% CI: 1.17, 1.71), respectively (P = 0.0015). The adjusted relative risk of incident hypertension was 1.08 (95% CI: 1.04, 1.13) for each mmol/L higher glucose (P < 0.0001) and 1.15 (95% CI: 1.05, 1.25) for each doubling of insulin (P = 0.0016). Further adjustment for serum cystatin C, urinary albumin/creatinine ratio, and arterial elasticity measured by tonometry substantially reduced the magnitudes of these associations. In conclusion, diabetes and higher concentrations of glucose and insulin may contribute to the development of hypertension, in part through kidney disease and arterial stiffness.

Serum calcium levels are tightly regulated. We performed genome-wide association studies (GWAS) in population-based studies participating in the CHARGE Consortium to uncover common genetic variations associated with total serum calcium levels. GWAS of serum calcium concentrations was performed in 20 611 individuals of European ancestry for ∼2.5 million genotyped and imputed single-nucleotide polymorphisms (SNPs). The SNP with the lowest P-value was rs17251221 (P = 2.4 * 10−22, minor allele frequency 14%) in the calcium-sensing receptor gene (CASR). This lead SNP was associated with higher serum calcium levels [0.06 mg/dl (0.015 mmol/l) per copy of the minor G allele] and accounted for 0.54% of the variance in serum calcium concentrations. The identification of variation in CASR that influences serum calcium concentration confirms the results of earlier candidate gene studies. The G allele of rs17251221 was also associated with higher serum magnesium levels (P = 1.2 * 10−3), lower serum phosphate levels (P = 2.8 * 10−7) and lower bone mineral density at the lumbar spine (P = 0.038), but not the femoral neck. No additional genomic loci contained SNPs associated at genome-wide significance (P < 5 * 10−8). These associations resemble clinical characteristics of patients with familial hypocalciuric hypercalcemia, an autosomal-dominant disease arising from rare inactivating mutations in the CASR gene. We conclude that common genetic variation in the CASR gene is associated with similar but milder features in the general population.

Background. Alcohol consumption appears to be protective for cardiovascular disease; however, its relationship with kidney disease is unclear.

Methods. This prospective cohort study included 4343 subjects from the Cardiovascular Health Study, a longitudinal, community-based cohort of persons aged ≥65 from four US communities. We used previously defined categories based on weekly alcohol consumption: none, former, <1 drink, 1–6 drinks, 7–13 drinks and ≥14 drinks. Cystatin C was measured at baseline, year 3 and year 7; eligible subjects had at least two measures. Estimated GFRcys was calculated from cystatin C. The primary outcome was rapid kidney function as an annual estimated GFR (eGFRcys) loss >3 mL/min/1.73 m2/year.

Results. Eight percent of the cohort reported former alcohol use and 52% reported current alcohol consumption. During a mean follow-up of 5.6 years, 1075 (25%) participants had rapid kidney function decline. In adjusted logistic regression models, there was no association between alcohol use and kidney function decline (odds ratio, 95% confidence interval: none = reference; former = 1.18, 0.89–1.56; <1 drink = 1.20, 0.99–1.47; 1–6 = 1.18, 0.95–1.45; 7–13 = 1.10, 0.80–1.53; >14 = 0.89, 0.61–1.13). Results were similar with kidney function decline as a continuous outcome.

Conclusions. Our results suggest that moderate alcohol consumption has neither adverse nor beneficial effects on kidney function. Although clinicians will need to consider the potential deleterious effects associated with alcohol consumption, there does not appear to be a basis for recommending that older adults discontinue or initiate light to moderate alcohol consumption to protect against kidney disease.

Background

Vitamin D is crucial for maintaining musculoskeletal health. Recently, vitamin D insufficiency has been linked to a number of extraskeletal disorders, including diabetes, cancer, and cardiovascular disease. Determinants of circulating 25-hydroxyvitamin D (25-OH D) include sun exposure and dietary intake, but its high heritability suggests that genetic determinants may also play a role.

Methods

We performed a genome-wide association study of 25-OH D among ∼30,000 individuals of European descent from 15 cohorts. Five cohorts were designated as discovery cohorts (n=16,125), five as in silico replication cohorts (n=9,366), and five as de novo replication cohorts (n=8,378). Association results were combined using z-score-weighted meta-analysis. Vitamin D insufficiency was defined as 25-OH D <75 nmol/L or <50 nmol/L.

Findings

Variants at three loci reached genome-wide significance in the discovery cohorts, and were confirmed in the replication cohorts: 4p12 (overall P=1.9 × 10-109 for rs2282679, in GC); 11q12 (P=2.1 × 10-27 for rs12785878, near DHCR7); 11p15 (P=3.3 × 10-20 for rs10741657, near CYP2R1). Variants at an additional locus (20q13, CYP24A1) were genome-wide significant in the pooled sample (P=6.0 × 10-10 for rs6013897). A genotype score was constructed using the three confirmed variants. Those in the top quartile of genotype scores had 2- to 2.5-fold elevated odds of vitamin D insufficiency (P≤1 × 10-26).

Interpretation

Variants near genes involved in cholesterol synthesis (DHCR7), hydroxylation (CYP2R1, CYP24A1), and vitamin D transport (GC) influence vitamin D status. Genetic variation at these loci identifies individuals of European descent who have substantially elevated risk of vitamin D insufficiency.

Background

In cross-sectional analyses, C-reactive protein (CRP) levels are inversely related to levels of kidney function. The relationship between kidney function and subsequent changes in CRP is unknown.

Methods

We studied 4,364 individuals from the Cardiovascular Health Study, a longitudinal cohort of community-dwelling older adults. Baseline eGFRcys was estimated using cystatin C. CRP was measured at baseline and after 3 and 7 years of follow-up; slopes of change in CRP were calculated.

Results

The mean (SD) age of the cohort was 72 (5.2) years; mean (SD) eGFRcys was 78.9 (18.4) ml/min/1.73 m2. The median (interquartile range IQR) baseline CRP was 2.39 (1.22, 4.33) mg/l; the median (IQR) yearly change in CRP was −0.0051 (−0.020 to 0.27) mg/l/year. After adjustment for demographic characteristics and the initial level of CRP, each standard deviation lower baseline eGFR was associated with a small and non-significant yearly increase in CRP (0.032 mg/l/year; 95% CI: −0.005 to 0.070, p = 0.094).

Conclusions

We did not find a relationship between eGFR and subsequent changes in CRP. The association between kidney function and CRP in cross-sectional analyses may reflect unmeasured confounding by atherosclerosis; alternatively, the burden of comorbidity and interval mortality in this population may have masked a stronger longitudinal association between kidney function and change in CRP. Further study in younger populations may clarify whether impaired kidney function leads to change in inflammation over time.

A higher serum phosphorus level is associated with cardiovascular disease (CVD) events among community-living populations. Mechanisms are unknown. The ankle-brachial index (ABI) provides information on both atherosclerosis and arterial stiffness. In this cross-sectional study (2000–2002), the authors evaluated the association of serum phosphorus levels with low (<0.90) and high (≥1.40 or incompressible) ABI as compared with intermediate ABI in 5,330 older US men, among whom the mean serum phosphorus level was 3.2 mg/dL (standard deviation, 0.4), 6% had a low ABI, and 5% had a high ABI. Each 1-mg/dL increase in serum phosphorus level was associated with a 1.6-fold greater prevalence of low ABI (95% confidence interval (CI): 1.2, 2.1; P < 0.001) and a 1.4-fold greater prevalence of high ABI (95% CI: 1.0, 1.9; P = 0.03) in models adjusted for demographic factors, traditional CVD risk factors, and kidney function. However, the association of phosphorus with high ABI differed by chronic kidney disease (CKD) status (in persons with CKD, prevalence ratio = 2.96, 95% CI: 1.61, 5.45; in persons without CKD, prevalence ratio = 1.14, 95% CI: 0.81, 1.61; interaction P = 0.04). In conclusion, among community-living older men, higher phosphorus levels are associated with low ABI and are also associated with high ABI in persons with CKD. These associations may explain the link between serum phosphorus levels and CVD events.

Background

Recent studies have demonstrated an association between moderate kidney dysfunction and sudden cardiac death in people with cardiovascular disease.

Methods and Results

The study was a longitudinal analysis among 4465 participants from the Cardiovascular Health Study without prevalent cardiovascular disease at baseline. Cystatin C and creatinine were measured from baseline sera. SCD was defined as a sudden pulseless condition from a cardiac origin in a previously stable individual that occurred out of the hospital or in the emergency room. The association between cystatin C tertiles and SCD was determined with multivariate Cox proportional hazards. A similar analysis compared SCD incidence across creatinine-based eGFR tertiles. Over a median follow-up of 11.2 years, 91 adjudicated SCD events occurred. The annual incidence of SCD events increased across cystatin C tertiles: 10 events per 10,000 person years in tertile 1, 25 events per 10,000 person years in tertile 2 and 32 events per 10,000 person years in the highest cystatin C tertile. These associations persisted after multivariate adjustment: [HR = 2.72, 95% CI (1.44–5.16) in tertile 2 and HR = 2.67, 95% CI (1.33–5.35) in tertile 3]. After multivariate adjustment, the rate of SCD also increased in a linear distribution across creatinine-based eGFR tertiles: 15 events per 10,000 person years in tertile 1, 22 events per 10,000 person years in tertile 2 and 27 events per 10,000 person years in tertile 3. No significant associations, however, remained between creatinine-based eGFR and SCD after multivariable adjustment.

Conclusion

Impaired kidney function, as measured by cystatin C, has an independent association with SCD risk among elderly persons without clinical cardiovascular disease.

Vitamin D shows promise for improving diverse health outcomes among patients with chronic kidney disease. Observational studies of vitamin D medications have contributed important evidence for broad beneficial clinical effects of vitamin D beyond actions on bone. However, such studies are limited by the potential for confounding by indication. A large randomized controlled trial is now needed to test the hypothesis that vitamin D therapy improves clinical outcomes in patients with kidney disease.

Background

Persons with early kidney disease have an increased risk of cardiovascular events and mortality, but the importance of accelerated atherosclerosis in promoting these outcomes is unclear. We therefore explored whether serum cystatin C level is associated with carotid intima-media thickness (IMT) in ambulatory adults without clinical heart disease.

Study Design

Cross-sectional study.

Setting & Participants

We evaluated 6,557 ethnically diverse persons free of clinical cardiovascular disease aged 45 to 84 years at the baseline visit of the Multi-Ethnic Study of Atherosclerosis.

Predictors

Kidney function was estimated by using 2 methods: serum cystatin C level and estimated glomerular filtration rate, based on creatinine and cystatin C levels.

Outcomes & Measurements

Study outcomes were internal and common carotid IMT, measured by using high-resolution B-mode ultrasound. Multivariate linear and logistic regressions were used to evaluate the independent association of kidney function with carotid IMT.

Results

In unadjusted linear analysis, each SD (0.23 mg/L) greater cystatin C level was associated with 0.091-mm greater internal carotid IMT (P < 0.001), but this association was diminished by 70% after adjustment for age, sex, and race/ethnicity (0.027 mm; P < 0.001) and was no longer significant after adjustment for cardiovascular risk factors (0.005 mm; P = 0.5). Similarly, the strong unadjusted associations of cystatin C level with common carotid IMT disappeared after adjustment. Chronic kidney disease, defined by using either creatinine level or cystatin C–based estimated glomerular filtration rate less than 60 mL/min/1.73 m2, had no independent association with internal and common carotid IMT.

Limitations

There were few participants with severe kidney disease.

Conclusions

Cystatin C level had no independent association with carotid IMT in a population free of clinical heart disease. This observation suggests that accelerated atherosclerosis is unlikely to be the primary mechanism explaining the independent association of cystatin C level with cardiovascular risk.

Objective

Experimental and epidemiologic studies suggest that calcium and vitamin D may reduce the risk of developing diabetes. We examined the effect of calcium plus vitamin D supplementation on the incidence of drug-treated diabetes in postmenopausal women.

Research Design and Methods

The Women's Health Initiative Calcium/Vitamin D Trial randomly assigned postmenopausal women to receive 1,000 mg elemental calcium plus 400 IU of vitamin D3 daily, or placebo, in a double-blind fashion. Among 33,951 participants without self-reported diabetes at baseline, we ascertained by treatment assignment new diagnoses of diabetes treated with oral hypoglycemic agents or insulin. Effects of the intervention on fasting measurements of glucose, insulin, and insulin resistance were examined among a subset of participants.

Results

Over a median follow-up time of 7 years, 2,291 women were newly diagnosed with diabetes. The hazard ratio for incident diabetes associated with calcium/vitamin D treatment was 1.01 (95% CI 0.94 –1.10) based on intention to treat. This null result was robust in subgroup analyses, efficacy analyses accounting for nonadherence, and analyses examining change in laboratory measurements.

Conclusions

Calcium plus vitamin D3 supplementation did not reduce the risk of developing diabetes over 7 years of follow-up in this randomized placebo-controlled trial. Higher doses of vitamin D may be required to affect diabetes risk, and/or associations of calcium and vitamin D intake with improved glucose metabolism observed in nonrandomized studies may be the result of confounding or of other components of foods containing these nutrients.

Background

Higher serum phosphorus concentrations within the normal laboratory range have been associated with cardiovascular events and mortality in large prospective cohort studies of individuals with and without kidney disease. Reasons for interindividual variation in steady-state serum phosphorus concentrations are largely unknown.

Study Design

Cross-sectional study.

Setting & Participants

15,513 participants in the Third National Health and Nutrition Examination Survey.

Predictors

Demographic data, dietary intake measured by means of 24-hour dietary recall and food-frequency questionnaire, and established cardiovascular risk factors.

Outcome & Measurements

Serum phosphorus concentration.

Results

Mean serum phosphorus concentrations were significantly greater in women (+0.16 mg/dL versus men; P < 0.001) and people of non-Hispanic black and Hispanic race/ethnicity (+0.06 and +0.07 mg/dL versus non-Hispanic white, respectively; P < 0.001). Dietary intakes of phosphorus and phosphorus-rich foods were associated only weakly with circulating serum phosphorus concentrations, if at all. Higher serum phosphorus levels were associated with lower calculated Framingham coronary heart disease risk scores, which are based on traditional atherosclerosis risk factors. In aggregate, demographic, nutritional, cardiovascular, and kidney function variables explained only 12% of the variation in circulating serum phosphorus concentrations.

Limitations

Results may differ with advanced kidney disease.

Conclusions

Serum phosphorus concentration is weakly related to dietary phosphorus and not related to a diverse array of phosphorus-rich foods in the general population. Factors determining serum phosphorus concentration are largely unknown. Previously observed associations of serum phosphorus concentrations with cardiovascular events are unlikely to be a result of differences in dietary intake or traditional cardiovascular risk factors.

Background

Kidney disease and hypertension commonly coexist, yet the direction of their association is still debated.

Objective

To evaluate whether early kidney dysfunction, measured by serum cystatin C levels and urinary albumin excretion, predates hypertension in adults without clinically recognized kidney or cardiovascular disease.

Design

Observational cohort study using data from 2000 to 2005.

Setting

The MESA (Multi-Ethnic Study of Atherosclerosis), a community-based study of subclinical cardiovascular disease in adults age 45 to 84 years.

Participants

2767 MESA participants without prevalent hypertension, cardiovascular disease, or clinically recognized kidney disease (an estimated glomerular filtration rate <60 mL/min per 1.73 m2 or microalbuminuria).

Measurements

Cystatin C was measured by using a nephelometer, and urinary albumin and creatinine were measured from a spot morning collection. The primary outcome was incident hypertension, defined as systolic blood pressure of at least 140 mm Hg, diastolic blood pressure of at least 90 mm Hg, or use of an antihypertensive medication.

Results

During a median follow-up of 3.1 years, 19.7% of the cohort (545 participants) developed hypertension. After adjustment for established hypertension risk factors, each 15-nmol/L increase in cystatin C was associated with a statistically significant 15% greater incidence of hypertension (P = 0.017). The highest sex-specific quartile of urinary albumin–creatinine ratio was associated with a statistically insignificant 16% greater incidence of hypertension (P = 0.192) compared with the lowest quartile. No statistical evidence suggested a multiplicative interaction.

Limitations

Unmeasured characteristics may have confounded observed associations of kidney markers with hypertension. Follow-up was relatively short. Hypertension that may have occurred between study visits or hypertension that was not captured by standard cuff measurements may have been missed.

Conclusion

Differences in kidney function, indicated by cystatin C levels, are associated with incident hypertension among individuals without clinical kidney or cardiovascular disease. These population-based findings complement experimental work implicating early kidney damage in the pathogenesis of essential hypertension.

We studied the incidence and progression of coronary artery calcification in people with early chronic kidney disease. We used a cohort of 562 adult patients with chronic kidney disease who had an estimated glomerular filtration rate of <60 ml/min/1.73 m2, in a community-based study of people without clinical cardiovascular disease, the Multi-Ethnic Study of Atherosclerosis. The majority had stage 3 disease. Coronary artery calcification was measured at baseline and again approximately 1.6 or 3.2 years later. The prevalence of coronary artery calcification at baseline was 66%, and its adjusted prevalence was 24% lower in African Americans as compared to Caucasians. The incidence of coronary artery calcification was 6.1% per year in women and 14.8% in men. Coronary artery calcification progressed in approximately 17% of subjects per year across all subgroups, and diabetes was associated with a 65% greater adjusted risk of progression. Male gender and diabetes were the only factors associated with adjusted coronary artery calcification incidence and progression, respectively. Our study shows that coronary artery calcification is common in people with stage 3 disease, progresses rapidly, and may contribute to cardiovascular risk.

Vascular abnormalities may exist before clinical hypertension. Using Poisson regression, the authors studied the association of coronary artery calcium (CAC), common carotid intima-media thickness (CIMT), aortic distensibility, and large and small arterial elasticity with incident hypertension among 2,512 normotensive US adults free of cardiovascular disease. Incidence rate ratios for incident hypertension (blood pressure ≥140/90 mm Hg or new antihypertensive medication) were calculated. Increased CAC was associated with incident hypertension in demographics-adjusted models (incidence rate ratio (IRR) = 1.35, 95% confidence interval (CI): 1.04, 1.75; IRR = 1.35, 95% CI: 1.02, 1.78; and IRR = 1.59, 95% CI: 1.12, 2.25 for CAC scores of 30–99, 100–399, and ≥400, respectively) but was attenuated after further adjustment. Increased common CIMT was associated with incident hypertension (IRR = 1.77, 95% CI: 1.28, 2.46 for quintile 4; IRR = 1.80, 95% CI: 1.28, 2.53 for quintile 5). Participants with the lowest, compared with the highest, aortic distensibility had an increased risk of hypertension (IRR = 1.75, 95% CI: 1.10, 2.79), as did those with the lowest large arterial elasticity (IRR = 1.49, 95% CI: 1.11, 1.99). Lower small arterial elasticity was incrementally associated with incident hypertension starting at quintile 2 (IRR = 2.01, 95% CI: 1.39, 2.91; IRR = 2.47, 95% CI: 1.71, 3.57; IRR = 2.73, 95% CI: 1.88, 3.95; and IRR = 2.85, 95% CI: 1.95, 4.16). Structural and functional vascular abnormalities are independent predictors of incident hypertension. These findings are important for understanding the pathogenesis of hypertension.

Background

Impaired kidney function is associated with increased risk for cardiovascular events. We evaluated whether kidney function is associated with atrial fibrillation (AF) risk in elderly persons.

Methods and Results

Subjects were participants in the Cardiovascular Health Study (CHS), a population-based cohort of ambulatory elderly. Measures of kidney function were cystatin C and creatinine-based estimated glomerular filtration rate (GFR). Among the 4663 participants, 342 (7%) had AF at baseline, and 579 (13%) developed incident AF during follow-up (mean 7.4 years). In unadjusted analyses cystatin C quartiles were strongly associated with prevalent AF with a nearly 3-fold odds in the highest quartile compared with the lowest [HR = 1.19, 95% CI (0.80-1.76) in quartile 2; HR = 2.00, 95% CI (1.38-2.88) in quartile 3; and HR = 2.87, 95% CI (2.03-4.07) in quartile 4]. This increased risk for prevalent AF remained significant after multivariate adjustment. The risk for incident AF increased across cystatin C quartiles in the unadjusted analysis [HR = 1.37, 95% CI (1.07-1.75) in quartile 2; HR = 1.43, 95% CI (1.11-1.84) in quartile 3; and HR = 1.88, 95% CI (1.47-2.41) in quartile 4]; however, after multivariate adjustment, these findings were no longer significant. Estimated GFR < 60 ml/min/1.73m2 was associated with prevalent and incident AF in unadjusted, but not multivariate analyses.

Conclusions

Impaired kidney function, as measured by cystatin C, is an independent marker of prevalent AF; however, neither cystatin C nor estimated GFR are predictors of incident AF.

Background. Cross-sectional studies have demonstrated a consistent and linear association between circulating inflammatory markers and kidney function. The objective of this study was to determine whether elevated markers of inflammation are independently associated with longitudinal kidney function decline.

Methods. This study included 4128 subjects from the Cardiovascular Health Study. Cystatin C was measured at baseline, 3 years later and 7 years later; eligible subjects had at least two measures. Cystatin C-based estimated glomerular filtration rate (eGFRcysC) was estimated, and rapid kidney function decline was defined as an annual loss of eGFRcysC >3 mL/min/1.73 m2. Predictors included ten inflammatory and procoagulant biomarkers: C-reactive protein, interleukin-6, intercellular adhesion molecule-1, white blood cell count, fibrinogen, factor VII, factor VIII, D-dimer, plasmin-antiplasmin complex and serum albumin.

Results. During the study, 1059 subjects (26%) had a rapid decline in kidney function. In contrast to the other nine inflammatory or procoagulant biomarkers, serum albumin had a consistent and inverse association with rapid kidney function decline [final adjusted logistic regression model: 1.14-fold increased odds (95% CI 1.06–1.23) of rapid decline per standard deviation lower albumin]. The lowest quartile of albumin had an odds ratio of 1.55 (95% CI 1.23–1.96) for rapid decline compared with the highest quartile. These associations persisted after adjusting the albumin models for CRP, IL-6 and fibrinogen.

Conclusions. In contrast to nine other inflammatory and procoagulant markers, only lower baseline levels of serum albumin were consistently associated with a rapid decline in kidney function, as measured by cystatin C-based eGFR.

Background

The prevalence of chronic kidney disease is growing most rapidly among older adults, but determinants of impaired kidney function in this population are not well understood. Obesity assessed in mid-life has been associated with chronic kidney disease.

Study design

Cohort study.

Setting & Participants

4,295 participants in the community-based Cardiovascular Health Study, ages >=65 years.

Predictors

Body mass index, waist circumference, and fat mass measured using bioelectrical impedance.

Outcome

Change in glomerular filtration rate (GFR) over 7 years of follow-up.

Measurements

Longitudinal estimates of GFR calculated with the 4-variable Modification of Diet in Renal Disease Study equation.

Results

Estimated GFR declined by an average of 0.4 +/− 3.6 mL/min/1.73m2/year, and rapid GFR loss (> 3 mL/min/1.73m2/year) occurred in 693 participants (16%). Baseline body mass index, waist circumference, and fat mass were each associated with increased risk of rapid GFR loss: odds ratios (95% confidence intervals) 1.19 (1.09, 1.30) per 5 kg/m2, 1.25 (1.16, 1.36) per 12 cm, and 1.14 (1.05, 1.24) per 10 kg, respectively, after adjustment for age, sex, race, and smoking. Magnitude of increased risk was larger for participants with estimated GFR < 60 mL/min/1.73m2 at baseline (p for interaction < 0.05). Associations were substantially attenuated by further adjustment for diabetes, hypertension, and C-reactive protein. Obesity measurements were not associated with change in GFR estimated using serum cystatin C.

Limitations

Few participants with advanced chronic kidney disease at baseline, no direct GFR measurements.

Conclusion

Obesity may be a modifiable risk factor for the development and progression of kidney disease among older adults.