Associations of segment-specific pulse wave velocity with vascular calcification: the Atherosclerosis Risk in Communities (ARIC) Study

Background

Pulse wave velocity (PWV) is a non-invasive measure of arterial stiffness and a predictor of cardiovascular disease (CVD). Vascular calcification, especially coronary artery calcium (CAC) measured by computed tomography (CT), is one of the strongest predictors of CVD but requires radiation for measurement. PWV may be helpful to identify persons with vascular calcification who may benefit from formal assessment of vascular calcification with CT. However, the associations between PWV and vascular calcification across different vascular beds have not been fully investigated.

Purpose

The aims of this study were to quantify the association between PWV and calcification at different segments and to explore whether PWV can identify individuals with vascular calcification beyond traditional risk factors.

Methods

Among 1486 ARIC Study participants (mean age 79.3 [SD 4.2] years), we measured PWV by OMRON VP1000plus at the following segments: heart-carotid (hcPWV), heart-femoral (hfPWV), carotid-femoral (cfPWV), heart-ankle (haPWV), brachial-ankle (baPWV) and femoral-ankle (faPWV). Participants were stratified into four groups based on quartiles of each PWV measure. Dependent (i.e., outcome) variables were high calcium score (≥75th percentile of Agatston score by CT) of the following vascular beds (including valves): coronary arteries, aortic valve ring, aortic valve, mitral valve, ascending aorta, and descending aorta. We ran multivariable logistic regression models and assessed c-statistics as a measure of prediction discrimination.

Results

Only cfPWV was significantly positively associated with high CAC (adjusted odds ratio [OR] for the highest vs. lowest quartile: 1.73 [95% CI: 1.17–2.55]) (green dot in figure). The associations were overall most evident for descending aorta calcification, with significantly positive results for hfPWV (gold dot in figure), cfPWV (green dot), haPWV (emerald dot), and baPWV (blue dot). For example, adjusted OR for the highest vs. lowest quartile of cfPWV was 4.08 (2.70–6.24). hfPWV and cfPWV were significantly associated with mitral valve calcification as well. In contrast, faPWV (purple dots) was inversely associated with calcification of aortic valve ring, ascending aorta, and descending aorta. For descending aorta calcification, even the second highest quartile of the following measures demonstrated significant adjusted OR: hfPWV (3.21 [2.11–4.95]), cfPWV (2.11 [1.40–3.20]), and baPWV (1.75 [1.14–2.69]). Simultaneously adding cfPWV and hfPWV improved c-statistic for CAC (Δc-statistic 0.011 [0.0007–0.022]) and descending aorta calcification (0.035 [0.017–0.053]).

Conclusions

The associations of PWV with vascular calcification varied substantially across segments, with descending aorta calcification most closely linked to PWV measures and cfPWV most robustly associated with calcification of multiple vascular beds. cfPWV and hfPWV, together, improved discrimination of high CAC beyond traditional risk factors.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The National Heart, Lung, and Blood Institute, National Institutes of Health

Including measures of chronic kidney disease to improve cardiovascular risk prediction by SCORE2 and SCORE2-OP

Background

The 2021 ESC guideline on cardiovascular disease (CVD) prevention qualitatively categorizes moderate and severe chronic kidney disease (CKD) as high and very-high CVD risk status regardless of other factors like age and does not include estimated glomerular filtration rate (eGFR) and albuminuria in its algorithms, SCORE2 and SCORE2-OP, to predict CVD risk.

Purpose

To develop and validate an “Add-on” to incorporate CKD measures into these algorithms, using a validated approach.

Methods

In 3,054,840 participants from 34 datasets, we developed three Add-ons (eGFR only, eGFR + urinary albumin-to-creatinine ratio [ACR] [the primary Add-on], and eGFR + dipstick proteinuria) for SCORE2 and SCORE2-OP. We validated c-statistics and net reclassification improvement (NRI), accounting for competing risk of non-CVD death, in 5,995,067 participants from 33 different datasets.

Results

In the target population of SCORE2 and SCORE2-OP without diabetes, the CKD Add-on (eGFR only) and CKD Add-on (eGFR + ACR) improved c-statistic by 0.006 (95% CI 0.005–0.008) and 0.018 (0.012–0.024), respectively, for SCORE2 and 0.012 (0.009–0.015) and 0.023 (0.013–0.032), respectively, for SCORE2-OP. Similar results were seen when we included individuals with diabetes and tested the CKD Add-on (eGFR + dipstick). In 57,485 European participants with CKD, SCORE2 or SCORE2-OP with a CKD Add-on showed a significant NRI (e.g., 0.100 [0.062–0.138] for SCORE2) compared to the qualitative approach in the ESC guideline.

Conclusion

Our Add-ons with CKD measures improved CVD risk prediction beyond SCORE2 and SCORE2-OP. This approach will help clinicians and patients with CKD refine risk prediction and further personalize preventive therapies for CVD.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): US National Kidney Foundation funding as well as US NIDDK

Abstract MP61: Greater Late-life Physical Function Declines Among Older Adults With Higher Blood Pressure In Mid-life: The Atherosclerosis Risk In Communities (ARIC) Study

Introduction: Greater late-life physical function decline is associated with incident adverse outcomes including disability and death. Hypertension is the strongest risk factor for stroke, the major cause of physical disability. Hypertension in mid-life has previously been associated with poor physical functioning in late-life; however, more evidence is needed to evaluate whether higher blood pressure in mid-life is associated with the rate of physical function decline during late-late in the absence of stroke. We hypothesized that elevated blood pressure in mid-life would be associated with greater physical function declines in late life.

Methods: We studied 5,559 older adults in the ARIC Study (Visit 5; mean age: 75.8 years; range: 66.7-90.9 years; 58% women; 21% Black/79% White) without prior stroke or Parkinson disease who completed the Short Physical Performance Battery (SPPB, scored 0-12). Repeated SPPB assessments occurred at Visits 6 and 7 (median follow-up: 4.2 years). The exposure was a history of elevated blood pressure (BP) (Visit 1; mean age: 52.0 years; mean gap between mid- and late-life exams: 23.7 years). BP was modeled both categorically (hypertensive: SBP 140+ mmHg, DBP 90+ mmHg, or antihypertensive medication use; pre-hypertensive: SBP 120-139 mmHg or DBP 80-89 mmHg; else normotensive) and continuously. Random-slope, random-intercept mixed models with an independent covariance structure tested the association between BP and SPPB score change, adjusted for age, sex, race-site, BMI, education, heart disease and heart failure. Continuous analysis also adjusted for antihypertensive medication use.

Results: SPPB scores declined an average of 1.60 points per 10 years (95% CI: -1.75, -1.46; p<0.001) among older adults who were normotensive in mid-life. Older adults with a previous measurement of hypertension declined an additional 0.94 points per 10 years (95% CI: -1.27, -0.60; p<0.001). Prehypertension was not statistically significantly associated with additional decline compared to mid-life normotension (estimate: -0.19 SPPB points/10 years; 95% CI: -0.53, 0.16; p=0.293). In the continuous analysis, each additional 10 mmHg higher mid-life systolic blood pressure above 120 mmHg was associated with an additional 0.24 point decline in SPPB per 10 years in late-life (95% CI: -0.31,-0.14; p<0.001).

Conclusions: Elevated BP in mid-life provides insight into the rate of physical function decline decades later, with higher mid-life systolic blood pressure corresponding with steeper declines in late-life physical function even in the absence of stroke. Future research should investigate whether elevated blood pressure at multiple points in mid-life further informs the association.

Liver enzymes, race, gender and diabetes risk: the Atherosclerosis Risk in Communities (ARIC) Study

AIMS

To examine the associations of the liver enzymes alanine aminotransferase (ALT), aspartate aminotransferase(AST), and gamma-glutamyl transferase (GGT) with diabetes risk and to determine whether associations differ by race and/or gender. We hypothesized that all liver enzymes would be associated with diabetes risk and that associations would differ by race and gender.

METHODS

Prospective cohort of 7495 white and 1842 black participants without diabetes in the Atherosclerosis Risk in Communities Study. Poisson and Cox models adjusted for demographic, socio-behavioural, and metabolic and health-related factors were used.

RESULTS

During a median of 12 years of follow-up, 2182 incident cases of diabetes occurred. Higher liver enzyme levels were independently associated with diabetes risk: adjusted hazard ratios (95% confidence intervals) were 1.68 (1.49-1.89), 1.16 (1.02-1.31) and 1.95 (1.70-2.24) comparing the highest with the lowest quartiles of ALT, AST, and GGT, respectively. Gamma-Glutamyl transferase was most strongly related to diabetes risk, even at levels considered within the normal range (≤ 60 U/l) in clinical practice. Adjusted incidence rates by quartiles of liver enzymes were similar by gender but higher in black versus white participants. Nonetheless, relative associations of ALT, AST, and GGT with diabetes were similar by race (P for interactions > 0.05).

CONCLUSIONS

Compared with ALT and AST, GGT was more strongly associated with diabetes risk. Our findings suggest that abnormalities in liver enzymes precede the diagnosis of diabetes by many years and that individuals with elevated liver enzymes, even within the normal range as defined in clinical practice, are at high risk for diabetes.

Early hospital readmission after kidney transplantation: patient and center-level associations

Early hospital readmission (EHR) is associated with increased morbidity, costs and transition-of-care errors. We sought to quantify rates of and risk factors for EHR after kidney transplantation (KT). We studied 32 961 Medicare primary KT recipients (2000-2005) linked to Medicare claims through the United States Renal Data System. EHR was defined as at least one hospitalization within 30 days of initial discharge after KT. The association between EHR and recipient and transplant factors was explored using Poisson regression; hierarchical modeling was used to account for study center-level differences. The overall EHR rate was 31%, and 19 independent patient-level factors associated with EHR were identified: recipient factors included older age, African American race and various comorbidities; transplant factors included ECD, length of stay and lack of induction therapy. The unadjusted rate of EHR by center ranged from 18% to 47%, but conventional center-level factors (percent African American, percent age > 60, percent deceased donor and percent expanded criteria donor) were not associated with EHR. However, intermediate total volume and average length of stay were associated with increased EHR risk. Better identification of patients at risk for early hospital readmission following KT may guide discharge planning and early posttransplant outpatient monitoring.

Risk factors for lacune subtypes in the Atherosclerosis Risk in Communities (ARIC) Study

OBJECTIVE

Lacunar infarctions are mainly due to 2 microvascular pathologies: lipohyalinosis and microatheroma. Little is known about risk factor differences for these subtypes. We hypothesized that diabetes and glycated hemoglobin (HbA(1)c) would be related preferentially to the lipohyalinotic subtype.

METHODS

We performed a cross-section analysis of the brain MRI data from 1,827 participants in the Atherosclerosis Risk in Communities study. We divided subcortical lesions ≤ 20 mm in diameter into those ≤ 7 mm (of probable lipohyalinotic etiology) and 8-20 mm (probably due to microatheroma) and used Poisson regression to investigate associations with the number of each type of lesion. Unlike previous studies, we also fitted a model involving lesions <3 mm.

RESULTS

Age (prevalence ratio [PR] 1.11 per year; 95% confidence interval [CI] 1.08-1.14), black ethnicity (vs white, PR 1.66; 95% CI 1.27-2.16), hypertension (PR 2.12; 95% CI 1.61-2.79), diabetes (PR 1.42; 95% CI 1.08-1.87), and ever-smoking (PR 1.34; 95% CI 1.04-1.74) were significantly associated with lesions ≤ 7 mm. Findings were similar for lesions <3 mm. HbA(1)c, substituted for diabetes, was also associated with smaller lesions. Significantly associated with 8-20 mm lesions were age (PR 1.14; 95% CI 1.09-1.20), hypertension (PR 1.79; 95% CI 1.14-2.83), ever-smoking (PR 2.66; 95% CI 1.63-4.34), and low-density lipoprotein (LDL) cholesterol (PR 1.27 per SD; 95% CI 1.06-1.52). When we analyzed only participants with lesions, history of smoking (PR 1.99; 95% CI 1.23-3.20) and LDL (PR 1.33 per SD; 95% CI 1.08-1.65) were associated with lesions 8-20 mm.

CONCLUSIONS

Smaller lacunes (even those <3 mm) were associated with diabetes and HbA(1)c, and larger lacunes associated with LDL cholesterol, differences which support long-held theories relating to their underlying pathology. The findings may contribute to broader understanding of cerebral microvascular disease.

Glycated haemoglobin and cognitive decline: the Atherosclerosis Risk in Communities (ARIC) study

AIMS/HYPOTHESIS

This study aimed to examine the association between diabetes and hyperglycaemia-assessed by HbA(1c)-and change in cognitive function in persons with and without diabetes.

METHODS

This was a prospective cohort study of 8,442 non-diabetic and 516 diabetic participants in the Atherosclerosis Risk in Communities (ARIC) study. We examined the association of baseline categories of HbA(1c) with 6 year change in three measures of cognition: the digit symbol substitution test (DSST); the delayed word recall test (DWRT); and the word fluency test (WFT). Our primary outcomes were the quintiles with the greatest annual cognitive decline for each test. Logistic regression models were adjusted for demographic (age, sex, race, field centre, education, income), lifestyle (smoking, drinking) and metabolic (adiposity, blood pressure, cholesterol) factors.

RESULTS

The mean age was 56 years. Women accounted for 56% of the study population and 21% of the study population were black. The mean HbA(1c) was 5.7% overall: 8.5% in persons with and 5.5% in persons without diabetes. In adjusted logistic regression models, diagnosed diabetes was associated with cognitive decline on the DSST (OR 1.42, 95% CI 1.14-1.75, p = 0.002), but HbA(1c) was not a significant independent predictor of cognitive decline when stratifying by diabetes diagnosis (diabetes, p trend = 0.320; no diabetes, p trend = 0.566). Trends were not significant for the DWRT or WFT in either the presence or the absence of diabetes.

CONCLUSIONS/INTERPRETATION

Hyperglycaemia, as measured by HbA(1c), did not add predictive power beyond diabetes status for 6 year cognitive decline in this middle-aged population. Additional work is needed to identify the non-glycaemic factors by which diabetes may contribute to cognitive decline.

NOS1AP variant associated with incidence of type 2 diabetes in calcium channel blocker users in the Atherosclerosis Risk in Communities (ARIC) study

AIMS/HYPOTHESIS

To validate the reported association between rs10494366 in NOS1AP (the gene encoding nitric oxide synthase-1 adaptor protein) and the incidence of type 2 diabetes in calcium channel blocker (CCB) users and to identify additional NOS1AP variants associated with type 2 diabetes risk.

METHODS

Data from 9 years of follow-up in 9,221 middle-aged white and 2,724 African-American adults free of diabetes at baseline from the Atherosclerosis Risk in Communities study were analysed. Nineteen NOS1AP variants were examined for associations with incident diabetes and fasting glucose levels stratified by baseline CCB use.

RESULTS

Prevalence of CCB use at baseline was 2.7% (n = 247) in whites and 2.3% (n = 72) in African-Americans. Among white CCB users, the G allele of rs10494366 was associated with lower diabetes incidence (HR 0.57, 95% CI 0.35-0.92, p = 0.016). The association was marginally significant after adjusting for age, sex, obesity, smoking, alcohol use, physical activity, hypertension, heart rate and electrocardiographic QT interval (HR 0.63, 95% CI 0.38-1.04, p = 0.052). rs10494366 was associated with lower average fasting glucose during follow-up (p = 0.037). No other variants were associated with diabetes risk in CCB users after multiple-testing correction. No associations were observed between any NOS1AP variant and diabetes development in non-CCB users. NOS1AP variants were not associated with diabetes risk in either African-American CCB users or non-CCB users.

CONCLUSIONS/INTERPRETATION

We have independently replicated the association between rs10494366 in NOS1AP and incident diabetes among white CCB users. Further exploration of NOS1AP variants and type 2 diabetes and functional studies of NOS1AP in type 2 diabetes pathology is warranted.

Risk of dementia hospitalisation associated with cardiovascular risk factors in midlife and older age: the Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND

Cardiovascular risk factors are associated with a higher risk of developing dementia. Studies in older populations, however, have often failed to show this relationship. We assessed the association between cardiovascular risk factors measured in midlife and risk of being hospitalised with dementia and determined whether this association was modified by age and ethnicity.

METHODS

We studied 11 151 participants in the population-based Atherosclerosis Risk in Communities cohort, aged 46-70 (23% African-Americans) in 1990-2, when participants underwent a physical exam and cognitive testing. Hospitalisations with dementia were ascertained through December 2004.

RESULTS

During follow-up, 203 cases of hospitalisation with dementia were identified. Smoking (hazard ratio (HR), 95% CI 1.7, 1.2 to 2.5), hypertension (HR, 95% CI 1.6, 1.2 to 2.2) and diabetes (HR, 95% CI 2.2, 1.6 to 3.0) were strongly associated with dementia, in Caucasians and African-Americans. These associations were stronger when risk factors were measured at a younger age than at an older age. In analyses including updated information on risk factors during follow-up, the HR of dementia in hypertensive versus non-hypertensive participants was 1.8 at age <55 years compared with 1.0 at age 70+ years. Parallel results were observed for diabetes (HR 3.4 in <55, 2.0 in >or=70), smoking (4.8 in <55, 0.5 in >or=70) and hypercholesterolaemia (HR 1.7 in <55, 0.9 in >or=70)

CONCLUSION

In this prospective study, smoking, hypertension and diabetes were strongly associated with subsequent risk of hospitalisation with dementia, particularly in middle-aged individuals. Our results emphasise the importance of early lifestyle modification and risk factor treatment to prevent dementia.

Retinal microvascular abnormalities and cognitive decline: the ARIC 14-year follow-up study

BACKGROUND

Because retinal and cerebral arterioles share similar pathologic processes, retinal microvascular changes are expected to be markers of cerebral small vessel disease (SVD). To better understand the role of SVD in cognitive function, we investigated the relationship between retinal microvascular abnormalities and longitudinal changes in cognitive function in a community-based study.

METHODS

A total of 803 participants underwent 4 cognitive assessments between 1990-1992 and 2004-2006, using the Word Fluency (WF) test, Digit Symbol Substitution (DSS), and Delayed Word Recall as well as retinal photography in 1993-1995. Covariate adjusted random effects linear models for repeated measures were used to determine the associations of cognitive change with specific retinal vascular abnormalities.

RESULTS

Individuals with retinopathy showed declines in executive function and psychomotor speed, with 1) an average decline in WF of -1.64 words per decade (95% confidence interval [CI] -3.3, -0.02) compared to no decline in those without retinopathy +0.06 (95% CI -0.6, 0.8) and 2) a higher frequency of rapid decliners on the DSS test.

CONCLUSION

Signs of retinal vascular changes, as markers of the cerebral microvasculature, are associated with declines in executive function and psychomotor speed, adding to the growing evidence for the role of microvascular disease in cognitive decline in the elderly.

HbA 1c as a risk factor for heart failure in persons with diabetes: the Atherosclerosis Risk in Communities (ARIC) study

AIMS/HYPOTHESIS

Heart failure (HF) incidence in diabetes in both the presence and absence of CHD is rising. Prospective population-based studies can help describe the relationship between HbA(1c), a measure of glycaemia control, and HF risk.

METHODS

We studied the incidence of HF hospitalisation or death among 1,827 participants in the Atherosclerosis Risk in Communities (ARIC) study with diabetes and no evidence of HF at baseline. Cox proportional hazard models included age, sex, race, education, health insurance status, alcohol consumption, BMI and WHR, and major CHD risk factors (BP level and medications, LDL- and HDL-cholesterol levels, and smoking).

RESULTS

In this population of persons with diabetes, crude HF incidence rates per 1,000 person-years were lower in the absence of CHD (incidence rate 15.5 for CHD-negative vs 56.4 for CHD-positive, p<0.001). The adjusted HR of HF for each 1% higher HbA(1c) was 1.17 (95% CI 1.11-1.25) for the non-CHD group and 1.20 (95% CI 1.04-1.40) for the CHD group. When the analysis was limited to HF cases which occurred in the absence of prevalent or incident CHD (during follow-up) the adjusted HR remained 1.20 (95% CI 1.11-1.29).

CONCLUSIONS/INTERPRETATIONS

These data suggest HbA(1c) is an independent risk factor for incident HF in persons with diabetes with and without CHD. Long-term clinical trials of tight glycaemic control should quantify the impact of different treatment regimens on HF risk reduction.

Chronic kidney disease as a global public health problem: approaches and initiatives - a position statement from Kidney Disease Improving Global Outcomes

Chronic kidney disease (CKD) is increasingly recognized as a global public health problem. There is now convincing evidence that CKD can be detected using simple laboratory tests, and that treatment can prevent or delay complications of decreased kidney function, slow the progression of kidney disease, and reduce the risk of cardiovascular disease (CVD). Translating these advances to simple and applicable public health measures must be adopted as a goal worldwide. Understanding the relationship between CKD and other chronic diseases is important to developing a public health policy to improve outcomes. The 2004 Kidney Disease Improving Global Outcomes (KDIGO) Controversies Conference on 'Definition and Classification of Chronic Kidney Disease' represented an important endorsement of the Kidney Disease Outcome Quality Initiative definition and classification of CKD by the international community. The 2006 KDIGO Controversies Conference on CKD was convened to consider six major topics: (1) CKD classification, (2) CKD screening and surveillance, (3) public policy for CKD, (4) CVD and CVD risk factors as risk factors for development and progression of CKD, (5) association of CKD with chronic infections, and (6) association of CKD with cancer. This report contains the recommendations from the meeting. It has been reviewed by the conference participants and approved as position statement by the KDIGO Board of Directors. KDIGO will work in collaboration with international and national public health organizations to facilitate implementation of these recommendations.

Three single-nucleotide polymorphisms in LPA account for most of the increase in lipoprotein(a) level elevation in African Americans compared with European Americans

BACKGROUND

The extent which universally common or population-specific alleles can explain between-population variations in phenotypes is unknown. The heritable coronary heart disease risk factor lipoprotein(a) (Lp(a)) level provides a useful case study of between-population variation, as the aetiology of twofold higher Lp(a) levels in African populations compared with non-African populations is unknown.

OBJECTIVE

To evaluate the association between LPA sequence variations and Lp(a) in European Americans and African Americans and to determine the extent to which LPA sequence variations can account for between-population variations in Lp(a).

METHODS

Serum Lp(a) and isoform measurements were examined in 534 European Americans and 249 African Americans from the Choices for Healthy Outcomes in Caring for End-Stage Renal Disease Study. In addition, 12 LPA variants were genotyped, including 8 previously reported LPA variants with a frequency of >2% in European Americans or African Americans, and four new variants.

RESULTS

Isoform-adjusted Lp(a) level was 2.23-fold higher among African Americans. Three single-nucleotide polymorphisms (SNPs) were independently associated with Lp(a) level (p<0.02 in both populations). The Lp(a)-increasing SNP (G-21A, which increases promoter activity) was more common in African Americans, whereas the Lp(a)-lowering SNPs (T3888P and G+1/inKIV-8A, which inhibit Lp(a) assembly) were more common in European Americans, but all had a frequency of <20% in one or both populations. Together, they reduced the isoform-adjusted African American Lp(a) increase from 2.23 to 1.37-fold(a 60% reduction) and the between-population Lp(a) variance from 5.5% to 0.5%.

CONCLUSIONS

Multiple low-prevalence alleles in LPA can account for the large between-population difference in serum Lp(a) levels between European Americans and African Americans.

Changes in serum calcium, phosphate, and PTH and the risk of death in incident dialysis patients: a longitudinal study

Elevated bone mineral parameters have been associated with mortality in dialysis patients. There are conflicting data about calcium, parathyroid hormone (PTH), and mortality and few data about changes in bone mineral parameters over time. We conducted a prospective cohort study of 1007 incident hemodialysis and peritoneal dialysis patients. We examined longitudinal changes in bone mineral parameters and whether their associations with mortality were independent of time on dialysis, inflammation, and comorbidity. Serum calcium, phosphate, and calcium-phosphate product (CaP) increased in these patients between baseline and 6 months (P<0.001) and then remained stable. Serum PTH decreased over the first year (P<0.001). In Cox proportional hazards models adjusting for inflammation, comorbidity, and other confounders, the highest quartile of phosphate was associated with a hazard ratio (HR) of 1.57 (1.07-2.30) using both baseline and time-dependent values. The highest quartiles of calcium, CaP, and PTH were associated with mortality in time-dependent models but not in those using baseline values. The lowest quartile of PTH was associated with an HR of 0.65 (0.44-0.98) in the time-dependent model with 6-month lag analysis. We conclude that high levels of phosphate both at baseline and over follow-up are associated with mortality in incident dialysis patients. High levels of calcium, CaP, and PTH are associated with mortality immediately preceding an event. Promising new interventions need to be rigorously tested in clinical trials for their ability to achieve normalization of bone mineral parameters and reduce deaths of dialysis patients.

Stability of haemoglobin A1c (HbA1c) measurements from frozen whole blood samples stored for over a decade

OBJECTIVE

Haemoglobin A1c (HbA1c), a measure of long-term glycaemic control, is at the centre of the clinical management of diabetes mellitus. However, the reproducibility of HbA1c measurements from whole blood samples which have been in long-term storage is unknown. We undertook this study to assess the reproducibility of HbA1c measurements from whole blood samples that had been in storage at -70 degrees C for over a decade.

RESEARCH DESIGN AND METHODS

Three hundred and thirty-six samples of frozen whole blood from the Atherosclerosis Risk in Communities (ARIC) Study, stored at -70 degrees C for 11-14 years assayed for HbA1c using a dedicated ion-exchange HPLC assay (Tosoh A1c 2.2 Plus HPLC) were compared with measurements on these same samples conducted prior to storage (in 1990-92) using a Diamat (Bio-Rad) HPLC instrument.

RESULTS

HbA1c measurements from long-term stored samples were strongly correlated with values obtained prior to long-term storage (r=0.97). The difference between HbA1c from long- and short-term stored samples had a mean of 0.35% HbA1c (sd=0.35) and a CV of 5.8%, which was approximately three times that of duplicate assays (CV 1.3 to 2.5%).

CONCLUSIONS

These data demonstrate that highly correlated but more variable and slightly higher HbA1c results were obtained from frozen whole blood samples that have been in storage for more than a decade. This highly reproducible assay performance would lead to comparable ranking of individuals and unbiased estimates of relative risks and odds ratios in epidemiological studies (case-control and cohort designs), but results should be realigned when the absolute value is of interest. These results have important implications for epidemiological studies and clinical trials which have stored whole blood specimens.

Undertreatment of hyperlipidemia in a cohort of United States kidney dialysis patients

BACKGROUND

Application of national guidelines regarding cardiovascular disease risk reduction to kidney dialysis patients is complicated by the conflicting observations that dialysis patients have a high risk of atherosclerotic cardiovascular disease (ASCVD), but dialysis patients with higher serum cholesterol have lower mortality rates. Actual treatment patterns of hyperlipidemia are not well studied.

METHODS

We assessed the prevalence, treatment and control of hyperlipidemia in this high-risk patient population from 1995 - 1998. We measured low-density lipoprotein cholesterol, treatment with a lipid-lowering agent, and prevalence of hyperlipidemia as defined by the National Cholesterol Education Program (NCEP), Adult Treatment Panel (ATP) II guidelines in 812 incident hemodialysis (HD), and peritoneal dialysis (PD) patients from dialysis clinics in 19 states throughout the United States.

RESULTS

Hyperlipidemia was present in 40% of HD and 62% of PD patients. Among subjects with hyperlipidemia, 67% of HD and 63% of PD patients were untreated and only 22% of HD and 14% of PD patients were treated and controlled. Those who entered the study in 1997 or 1998, those with diabetes, males and Caucasians were more likely to be treated and controlled, whereas subjects on PD and those with ASCVD were less likely to be treated and controlled.

CONCLUSION

These data suggest that high rates of undertreatment exist in the United States ESRD dialysis population. Whether improved rates of treatment will result in decreased cardiovascular disease events needs to be tested in randomized clinical trials.

Timing of nephrologist referral and arteriovenous access use: the CHOICE Study

Recent clinical practice guidelines recommend the creation of an arteriovenous (AV) vascular access (ie, native fistula or synthetic graft) before the start of chronic hemodialysis therapy to prevent the need for complication-prone dialysis catheters. We report on the association of referral to a nephrologist with duration of dialysis-catheter use and type of vascular access used in the first 6 months of hemodialysis therapy. The study population is a representative cohort of 356 patients with questionnaire, laboratory, and medical record data collected as part of the Choices for Healthy Outcomes in Caring for End-Stage Renal Disease Center Study. Patients who reported being seen by a nephrologist at least 1 month before starting hemodialysis therapy (75%) were more likely than those referred later to use an AV access at initiation (39% versus 10%; P < 0.001) and 6 months after starting hemodialysis therapy (74% versus 56%; P < 0.01). Patients referred within 1 month of initiating hemodialysis therapy used a dialysis catheter for a median of 202 days compared with 64, 67, and 19 days for patients referred 1 to 4, 4 to 12, and greater than 12 months before initiating hemodialysis therapy, respectively (P trend < 0.001). Patients referred at least 4 months before initiating hemodialysis therapy were more likely than patients referred later to use an AV fistula, rather than a synthetic graft, as their first AV access (45% versus 31%; P < 0.01). These associations remained after adjustment for age, sex, race, marital status, education, insurance coverage, comorbid disease status, albumin level, body mass index, and underlying renal diagnosis. These data show that late referral to a nephrologist substantially increases the likelihood of dialysis-catheter use at the initiation of hemodialysis therapy and is associated with prolonged catheter use. Regardless of the time of referral, only a minority of patients used an AV access at the initiation of treatment, and greater than 25% had not used an AV access 6 months after initiation. Thus, further efforts to improve both referral patterns and preparation for dialysis after referral are needed.

Prevalence of high blood pressure and elevated serum creatinine level in the United States: findings from the third National Health and Nutrition Examination Survey (1988-1994)

BACKGROUND

The prevalence and incidence of end-stage renal disease in the United States are increasing, but milder renal disease is much more common and may often go undiagnosed and undertreated.

METHODS

A cross-sectional study of a representative sample of the US population was conducted using 16 589 adult participants aged 17 years and older in the Third National Health and Nutrition Examination Survey (NHANES III) conducted from 1988 to 1994. An elevated serum creatinine level was defined as 141 micromol/L or higher (>/=1.6 mg/dL) for men and 124 micromol/L or higher (>/=1.4 mg/dL) for women (>99th percentile for healthy young adults) and was the main outcome measure.

RESULTS

Higher systolic and diastolic blood pressures, presence of hypertension, antihypertensive medication use, older age, and diabetes mellitus were all associated with higher serum creatinine levels. An estimated 3.0% (5.6 million) of the civilian, noninstitutionalized US population had elevated serum creatinine levels, 70% of whom were hypertensive. Among hypertensive individuals with an elevated serum creatinine level, 75% received treatment. However, only 11% of all individuals with hypertension had their blood pressure reduced to lower than 130/85 mm Hg (the Sixth Report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure recommendation for hypertensive individuals with renal disease); 27% had a blood pressure lower than 140/90 mm Hg. Treated hypertensive individuals with an elevated creatinine level had a mean blood pressure of 147/77 mm Hg, 48% of whom were prescribed one antihypertensive medication.

CONCLUSION

Elevated serum creatinine level, an indicator of chronic renal disease, is common and strongly related to inadequate treatment of high blood pressure.

Associations of tibia lead, DMSA-chelatable lead, and blood lead with measures of peripheral nervous system function in former organolead manufacturing workers

BACKGROUND

The goals of the present study were to compare and contrast associations of blood lead, DMSA-chelatable lead, current tibia lead, and back-extrapolated "peak" tibia lead with four peripheral nervous system (PNS) sensory and motor function measures in older males with past exposure to organic and inorganic lead.

METHODS

Data were collected from former organolead manufacturing workers with an average of 16 years since last occupational lead exposure. Current tibia lead levels were measured by (109)Cd x-ray fluorescence. Sensory pressure thresholds (index and pinky fingers) and pinch and grip strength were measured with the Pressure-Specified Sensory Device (PSSD).

RESULTS

In adjusted analyses, none of the four lead biomarkers was associated with sensory pressure threshold of the index finger or pinch or grip strength. In contrast, all four biomarkers were associated (P < or = 0.10) with pressure threshold of the pinky finger. The final linear regression models accounted for a small proportion of the variance in the sensory (1-3%) and motor measures (10-21%).

CONCLUSIONS

This study found no strong association between lead biomarkers and selected PNS sensory or motor function measures among former organolead manufacturing workers with no recent occupational exposure to lead. Previously reported CNS findings in this cohort suggest that the PNS may be less sensitive to the chronic toxic effects of lead in this dose range among adults. It is also possible that the PNS has a greater capacity for repair than does the CNS, or that the PNS measures were less sensitive for detection of lead-related health outcomes than were the CNS measures.

Relation between gender and vascular access complications in hemodialysis patients

Native arteriovenous (AV) fistulae for hemodialysis vascular access are believed to be associated with fewer complications than synthetic polytetrafluoroethylene (PTFE) grafts. We conducted a study among patients in the Dialysis Morbidity and Mortality Study to compare risk factors for complications of AV fistulae and PTFE grafts in men and women and to examine the effect of age on vascular access complications. We analyzed data from 833 incident patients with end-stage renal disease who had a PTFE graft (n = 621) or AV fistula (n = 212) in use 1 month after starting hemodialysis therapy. Follow-up using inpatient and outpatient Medicare administrative data identified a 1.8-times greater risk for a subsequent vascular access procedure for PTFE grafts (0.71 procedures/access-year) than for AV fistulae (0.39 procedures/access-year). Men with grafts and women with grafts or fistulae had a greater risk for a first subsequent access procedure than did men with fistulae (0.79, 0.65, and 0.59 versus 0.33 procedures/access-year, respectively). After adjustment for age, race, presence of diabetes mellitus, and history of smoking, peripheral vascular disease, and cardiovascular disease, use of a PTFE graft compared with an AV fistula was associated with a greater risk for a first subsequent procedure in men (relative hazard, 2.2; 95% confidence interval [CI], 1.6 to 2.9), but not in women (relative hazard, 1.0; 95% CI, 0.7 to 1.4). The excess risk associated with a PTFE graft compared with an AV fistula was limited to men in the lower three quartiles of age (ie, </=72 years). These data raise concern that the potential benefits of AV fistulae over PTFE grafts are not realized in women and older men. A better understanding of the determinants of successful access maturation and maintenance in these groups is needed.

Relationship between skin color and blood pressure in egyptian adults: results from the national hypertension project

In many, but not all societies, dark skin color is associated with high blood pressure. Whether the association between skin color and blood pressure is independent of known determinants of blood pressure remains controversial. We examined the association between skin color and blood pressure in 835 Egyptian adults (370 men and 465 women) participating in the National Hypertension Project, a national survey of hypertension prevalence and blood pressure-related complications conducted in Egypt during 1991-1993. Skin color was assessed by measuring the concentration of cutaneous melanin in an unexposed area with the use of reflectance spectrophotometry. Higher concentrations of melanin were associated with lower body mass index, less education, manual labor (among men), and a lower urinary sodium-to-potassium ratio (among women). In multivariate regression analyses adjusted for age, body mass index, and education, there was a significant nonlinear association between blood pressure and skin color among women; in the lower to intermediate range of skin pigmentation, both systolic and diastolic blood pressures were higher in women with greater concentrations of cutaneous melanin. In men, blood pressure was not associated with skin color. When we used a subjective assessment of skin color, there was no significant difference in blood pressure between black-skinned Egyptians (predominantly of Nubian descent) and fair-skinned Egyptians for either gender. While the significant relationship in women appeared to be independent of known risk factors for hypertension, residual confounding may explain the association.

Plasma lipids and risk of developing renal dysfunction: the atherosclerosis risk in communities study

BACKGROUND

Animal and in vitro data suggest that dyslipidemia plays an important role in the initiation and progression of chronic renal disease, but few prospective studies have been conducted in humans.

METHODS

We studied the relationship of plasma lipids to a rise in serum creatinine of 0.4 mg/dL or greater in 12,728 Atherosclerosis Risk in Communities (ARIC) participants with baseline serum creatinine that was less than 2.0 mg/dL in men and less than 1.8 mg/dL in women.

RESULTS

During a mean follow-up of 2.9 years, 191 persons had a rise in creatinine of 0.4 mg/dL or greater, yielding an incidence rate of 5.1 per 1000 person years. Individuals with higher triglycerides and lower high-density lipoprotein (HDL) and HDL-2 cholesterol at baseline were at increased risk for a rise in creatinine after adjustment for race, gender, baseline age, diabetes, serum creatinine, systolic blood pressure, and antihypertensive medication use (all P trends </=0.02). The adjusted relative risk for the highest versus lowest quartile of triglycerides was 1.65 (95% CI, 1.1, 2.5, P = 0.01) and for HDL was 0.47 (95% CI, 0.3, 0.8, P = 0.003). These associations were significant in participants with normal creatinine (defined as <1.4 mg/dL for men and <1.2 mg/dL for women), with diabetes, and without diabetes. The effect of high triglycerides was independent of plasma glucose, but was weaker and less consistent after further adjustment for fasting insulin in nondiabetics.

CONCLUSIONS

High triglycerides and low HDL cholesterol, but not low-density lipoprotein cholesterol, predict an increased risk of renal dysfunction. The treatment of these lipid abnormalities may decrease the incidence of early renal disease.

A comprehensive analysis of complex traits in problem 2A

We used descriptive analysis to investigate the relationship between affection status and five quantitative traits (Q1-Q5) in Problem 2A and results suggested the five quantitative traits fall into two groups. The first group comprised three strongly correlated traits, Q1-Q3, which underlie affection status, and the second group comprised Q4 and Q5, which are not directly related to affection status. Segregation and linkage analyses of traits Q1-Q3 and affection status from the first replicate detected one of the major loci for Q1 (MG1) linked to marker 14 on chromosome 5 (D5G14). Because our segregation analysis failed to show evidence of a major locus effect on Q2, and we overlooked the interaction between MG3 and sex, we did not detect either MG2 or MG3. Using Haseman-Elston sib-pair analysis [Haseman and Elston, 1972], we also examined the statistical power of Q1 and type I error rate (using the environmental factor as an index), for the remaining 199 replicates in the context of a genome screen.

No common major gene for apolipoprotein A-I and HDL3-C levels: evidence from bivariate segregation analysis

Apolipoprotein A-I (apo A-I) is the most abundant protein in high-density lipoprotein (HDL) particles, and it plays an important role in HDL metabolism. Both apo A-I and HDL cholesterol (HDL-C) levels are inversely associated with risk of cardiovascular disease. Segregation analyses suggest apo A-I levels are under the control of one or more major loci. Since HDL particles are heterogeneous in their composition and size, genetic influence on its subfractions (i.e., HDL2 and HDL3) could vary. A previous report showed evidence of a major locus controlling HDL3-C levels in a subset of the current study population. Because quantitative trait loci involved in complex diseases are likely to have pleiotropic effects on several related traits, it is possible to have a common major gene involved in regulating apo A-I and HDL3-C levels. We performed a bivariate segregation analysis of apo A-I and HDL3-C levels in 1,006 individuals from 137 families ascertained through probands undergoing elective, diagnostic coronary angiography at the Johns Hopkins Hospital. The results showed significant genetic correlation between these two traits, but the hypothesis of a common major gene was rejected. Bivariate segregation analysis favored a model with two genes controlling apo A-I and a third gene independently controlling HDL3-C, and the genetic correlation between these two traits is due to residual additive polygenes. Overall, results from this study suggest that there are distinct genetic mechanisms for apo A-I and HDL3-C levels. Future studies, especially linkage analysis, should consider distinct genetic mechanisms and multiple major gene loci.

Segregation analysis of two-locus models regulating apolipoprotein-A1 levels

For quantitative traits associated with risk to complex diseases, such as heart disease, single major locus models are likely to be too simplistic. Currently, researchers have begun to use oligogenic models of inheritance, but the resolving power of these models remains to be determined. As the major apoprotein of high density lipoprotein (HDL), apolipoprotein A1 (apo-A1) is generally accepted as a protective factor for coronary artery disease. Although familial aggregation of apo-A1 levels has been reported, the mode of inheritance of apo-A1 remains ill defined. In the present study, we conducted a segregation analysis comparing a series of one-locus and two-locus univariate models for apo-A1 levels in a sample of 137 families ascertained through probands undergoing elective, diagnostic coronary angiography. A two-locus Mendelian model fit these data significantly better than any one-locus model. The incorporation of the second major locus into the model of inheritance leads to a significant improvement in the fit, and a significant decrease of the residual heritability. The best-fitting model included two loci with a reciprocal pattern of epistasis generating 4 distinct genotypic distributions. Taken together, these two major loci account for 58% of the variance of adjusted apo-A1 levels. This demonstration of a second major locus controlling apo-A1 levels may explain the equivocal results obtained from previous studies. This two-locus model may be more powerful for linkage analysis to map one or both of these quantitative trait loci.

Randomized double-blind trial of oral essential amino acids for dialysis-associated hypoalbuminemia

BACKGROUND

Hypoalbuminemia is associated with substantial morbidity and mortality in dialysis patients.

METHODS

Subjects with a mean three-month prestudy serum albumin of 3.8 g/dL or less and who demonstrated >/=90% compliance during a two-week run-in period were randomized to 3.6 g of essential amino acids (EAAs) or placebo three times daily with meals for three months. Randomization was stratified by dialysis modality and by severity of the hypoalbuminemia. The primary study outcome was change in the average of three monthly serum albumin measurements between baseline and follow-up.

RESULTS

Fifty-two patients were randomized; 47 patients (29 hemodialysis and 18 peritoneal dialysis) met the predetermined primary analysis criteria. The mean compliance rates averaged 75, 70, and 50% at months 1, 2, and 3, respectively, and were similar for EAAs and placebo. Serum albumin in the hemodialysis patients, EAA versus placebo, improved [(mean +/- SE) 0.22 +/- 0.09 g/dL, P = 0.02]. Changes in peritoneal dialysis patients were not significant (0.01 +/- 0.15 g/dL), but approached significance for the total study group (0.14 +/- 0.08 g/dL, P = 0.08). Patients in the very low albumin strata (<3.5 g/dL) improved more than those in the low albumin strata (3.5 to 3.8 g/dL, P < 0.01). There was a significant correlation (r = 0.83, P = 0.001) within the hemodialysis EAA group between the baseline C-reactive protein level and improvement in serum albumin. Improvements were also seen in grip strength and SF-12 mental health score, but not in serum amino acid levels, SF-12 physical health score, or anthropometric measurements.

CONCLUSIONS

Oral EAAs induce a significant improvement in the serum albumin concentration in hemodialysis but not peritoneal dialysis subjects. Further study of their long-term effects on morbidity and mortality is warranted.

Lack of benefit for intravenous thrombolysis in patients with myocardial infarction who are older than 75 years

BACKGROUND

The benefit of intravenous thrombolytic therapy in elderly patients with myocardial infarction is uncertain. There are no randomized trials of thrombolytic efficacy or observational studies of clinical effectiveness that focus specifically on the elderly.

METHODS AND RESULTS

To determine whether thrombolytic therapy for elderly patients is associated with a survival advantage in a large observational database, we conducted a retrospective cohort study of 7864 Medicare fee-for-service patients aged 65 to 86 years with the primary discharge diagnosis of acute myocardial infarction who were admitted with clinical and ECG indications for thrombolytic therapy and no absolute contraindications. The study included all US acute care nongovernment hospitals without on-site angioplasty capability. Using proportional-hazards methods, we found that in a comprehensive multivariate model, there was a significant interaction (P<0.001) between age and the effect of thrombolytic therapy on 30-day mortality rates. For patients 65 to 75 years old, thrombolytic therapy was associated with a survival benefit, consistent with randomized trials. Among patients aged 76 to 86 years, thrombolytic therapy was associated with a survival disadvantage, with a 30-day mortality hazard ratio of 1.38 (95% CI 1. 12 to 1.71, P=0.003). For these patients, there was no benefit from thrombolytic therapy in any clinical subgroup.

CONCLUSIONS

In nationwide clinical practice, thrombolytic therapy for patients >75 years old is unlikely to confer survival benefit and may have a significant survival disadvantage. Reperfusion research that is focused on elderly patients is urgently needed.

Risk factors for hypercreatinemia in patients with systemic lupus erythematosus

Renal insufficiency is one of the most severe outcomes of systemic lupus erythematosus (SLE). The aim of this study was to identify baseline predictors of the development of renal insufficiency in a cohort of patients with SLE. 281 patients from the The Hopkins Lupus Cohort (HLC) enrolled between 1987-1994 were followed for the occurrence of renal insufficiency, defined as a serum creatinine 1.6 mg/dl for men and 1.4 mg/dl for women. Over a mean (+/-s.d.) of 3. 3+/-2.1 y of follow up, 46 (16%) of the 281 patients developed renal insufficiency. Using a multivariate Cox proportional hazard model, we found the risk of renal insufficiency associated with younger (0-19 y) or older (40 y) age at baseline (relative risk (95% CI) 5.1 (1.4, 18.8) and 4.1 (2.1, 8.2)) and longer duration of SLE before referral to the cohort (RR 1.25 [1.05, 1.5] for every five years). Additional predictive variables were borderline elevation of serum creatinine at baseline (RR 3.1 (1.4, 6.6) for a serum creatinine 1. 4-1.5 mg/dl for men and 1.2-1.3 mg/dl for women), and mean proteinuria (RR 3.6 (1.8, 7.4) for trace-3+ and 10.6 (3.8, 30.0) for 3+ (urine dipstick level)). Socioeconomic status, race, autoantibodies and complement were not significantly associated with the risk of renal insufficiency. This study supports early referral of SLE patients to rheumatologists and emphasizes the importance of early signs of renal involvement as predictors of later renal insufficiency in SLE patients.

Variants of the insulin receptor substrate-1 and fatty acid binding protein 2 genes and the risk of type 2 diabetes, obesity, and hyperinsulinemia in African-Americans: the Atherosclerosis Risk in Communities Study

We conducted a community-based case-control study of African-American men and women in the Atherosclerosis Risk in Communities Study. The allele frequencies of the Gly972Arg variant of the insulin receptor substrate-1 (IRS-1) gene and the Ala54Thr variant of the fatty acid binding protein 2 (FABP2) gene were compared in 992 normal control subjects and three patient groups: 1) 321 type 2 diabetic individuals, 2) 260 severely obese individuals, and 3) 258 markedly hyperinsulinemic individuals without diabetes. Allele frequencies of Gly972Arg IRS-1 and Ala54Thr FABP2 were 0.07 and 0.22, respectively; there were no differences in allele or genotype frequencies between patients and control subjects for either gene variant. In weighted linear regression of all patients and control subjects, the presence of the IRS-1 gene variant was associated with a 0.85 (0.42) kg/m2 higher BMI (P = 0.04). In addition, individuals with at least one IRS-1 Arg972 allele and two FABP2 Thr54 alleles had a BMI of 33.3 (7.9) kg/m2, compared with 30.0 (6.3) kg/m2 for those with neither allele (P = 0.05). These results suggest that in African-Americans, these variants in the IRS-1 and FABP2 genes are not associated with the risk of type 2 diabetes, severe obesity, or marked hyperinsulinemia, but that their independent and joint effects may be associated with small increases in BMI.

A community-based study of explanatory factors for the excess risk for early renal function decline in blacks vs whites with diabetes: the Atherosclerosis Risk in Communities study

CONTEXT

The explanation for the excess risk for diabetic renal disease in blacks is uncertain.

OBJECTIVES

To compare the incidence of early renal function decline in black and white adults with diabetes and to examine possible explanatory factors for racial differences.

DESIGN

Prospective cohort study.

SETTING

Four US communities participating in the Atherosclerosis Risk in Communities study.

PARTICIPANTS

Community-based sample of 1434 diabetic adults aged 45 to 64 years.

MEASUREMENTS

Detailed baseline assessment using structured interview, results of physical examination, and laboratory measurements.

MAIN OUTCOME

Development of early renal function decline defined by an increase in serum creatinine of at least 35.4 micromol/L (0.4 mg/dL) during 3 years of follow-up.

RESULTS

During 3 years of follow-up, early renal function decline developed in 45 blacks (28.4 per 1000 person-years [PY]) and 25 whites (9.6 per 1000 PY). After adjustment for age, sex, and baseline serum creatinine level, early renal function decline was more than 3 times as likely to develop in blacks than whites (odds ratio, 3.15; 95% confidence interval, 1.86-5.33). Additional adjustment for education, household income, health insurance, fasting glucose level, mean systolic blood pressure, smoking history, and physical activity level reduced the relative odds in blacks to 1.38 (95% confidence interval, 0.71-2.69), corresponding to a 82% reduction in excess risk.

CONCLUSIONS

These data suggest that early renal function decline is 3 times more likely to develop in blacks than whites and that potentially modifiable factors, including lower socioeconomic status, suboptimal health behaviors, and suboptimal control of glucose level and blood pressure, account for more than 80% of this disparity.

The association between hospital volume and survival after acute myocardial infarction in elderly patients

BACKGROUND

Patients with chest pain thought to be due to acute coronary ischemia are typically taken by ambulance to the nearest hospital. The potential benefit of field triage directly to a hospital that treats a large number of patients with myocardial infarction is unknown.

METHODS

We conducted a retrospective cohort study of the relation between the number of Medicare patients with myocardial infarction that each hospital in the study treated (hospital volume) and long-term survival among 98,898 Medicare patients 65 years of age or older. We used proportional-hazards methods to adjust for clinical, demographic, and health-system-related variables, including the availability of invasive procedures, the specialty of the attending physician, and the area of residence of the patient (rural, urban, or metropolitan).

RESULTS

The patients in the quartile admitted to hospitals with the lowest volume were 17 percent more likely to die within 30 days after admission than patients in the quartile admitted to hospitals with the highest volume (hazard ratio, 1.17; 95 percent confidence interval, 1.09 to 1.26; P<0.001), which resulted in 2.3 more deaths per 100 patients. The crude mortality rate at one year was 29.8 percent among the patients admitted to the lowest-volume hospitals, as compared with 27.0 percent among those admitted to the highest-volume hospitals. There was a continuous inverse dose-response relation between hospital volume and the risk of death. In an analysis of subgroups defined according to age, history of cardiac disease, Killip class of infarction, presence or absence of contraindications to thrombolytic therapy, and time from the onset of symptoms, survival at high-volume hospitals was consistently better than at low-volume hospitals. The availability of technology for angioplasty and bypass surgery was not independently associated with overall mortality.

CONCLUSIONS

Patients with acute myocardial infarction who are admitted directly to hospitals that have more experience treating myocardial infarction, as reflected by their case volume, are more likely to survive than are patients admitted to low-volume hospitals.

The effects of rifampin and rifabutin on the pharmacokinetics and pharmacodynamics of a combination oral contraceptive

BACKGROUND

Rifampin (INN, rifampicin), a CYP34A inducer, results in significant interactions when coadministered with combination oral contraceptives that contain norethindrone (INN, norethisterone) and ethinyl estradiol (INN, ethinylestradiol). Little is known about the effects of rifabutin, a related rifamycin.

OBJECTIVES AND METHODS

The relative effects of rifampin and rifabutin on the pharmacokinetics and pharmacodynamics of ethinyl estradiol and norethindrone were evaluated in a prospective, randomized, double-blinded crossover study in 12 premenopausal women who were on a stable oral contraceptive regimen that contained 35 microg ethinyl estradiol/1 mg norethindrone. Subjects were randomized to receive 14 days of rifampin or rifabutin from days 7 through 21 of their menstrual cycle. After a 1-month washout period (only the oral contraceptives were taken), subjects were crossed over to the other rifamycin.

RESULTS

Rifampin significantly decreased the mean area under the plasma concentration-time curve from time 0 to 24 hours [AUC(0-24)] of ethinyl estradiol and the mean AUC(0-24) of norethindrone. Rifabutin significantly decreased the mean AUC(0-24) of ethinyl estradiol and the mean AUC(0-24) of norethindrone. The effect of rifampin was significantly greater than rifabutin on each AUC(0-24). Despite these changes, subjects did not ovulate (as determined by progesterone concentrations) during the cycle in which either rifamycin was administered. Levels of mean follicle-stimulating hormone increased 69% after rifampin.

CONCLUSION

In this study, rifampin (600 mg daily) was a more significant inducer of ethinyl estradiol and norethindrone clearance than rifabutin (300 mg daily), but neither agent reversed the suppression of ovulation caused by oral contraceptives. The carefully monitored oral contraceptive administration and the limited exposure to rifamycins may restrict the application of this study to clinical situations.

Use of cardiovascular procedures among black persons and white persons: a 7-year nationwide study in patients with renal disease

BACKGROUND

Black persons historically undergo fewer invasive cardiovascular procedures than white persons.

OBJECTIVE

To determine whether acquisition of Medicare health insurance and comprehensive care for severe illness reduce ethnic disparity in use of cardiovascular procedures.

DESIGN

7-year longitudinal analyses in a cohort from the United States Renal Data System.

SETTING

Health care institutions in the United States.

PATIENTS

Nationwide random sample of 4987 adult black and white patients with incident end-stage renal disease (ESRD) from 303 dialysis facilities in 1986 to 1987.

MEASUREMENTS

Medical history and service use records, physical examination, and laboratory data. Main outcome measures were receipt of a coronary catheterization or revascularization procedure before (baseline) and after (follow-up) development of ESRD and acquisition of Medicare, adjusted for clinical and socioeconomic variables.

RESULTS

At baseline, 9.9% of white patients and 2.8% of black patients had had a cardiac procedure; the odds were almost three times greater in white than in black patients (adjusted odds ratio, 2.92 [95% CI, 2.04 to 4.18]). During follow-up, white patients were only 1.4 times more likely than black patients to have a procedure (adjusted relative risk, 1.41 [CI, 1.13 to 1.77]); rates were 7.8% for white persons and 8.5% for black persons. In patients with Medicare coverage before development of ESRD, the initial three-fold difference in procedure use was eliminated over follow-up (odds ratio, 1.05 [CI, 0.56 to 1.60]). For procedures after hospital admission for myocardial infarction or coronary disease, no difference between ethnic groups was seen during follow-up (relative risk, 1.12 [CI, 0.68 to 1.85]).

CONCLUSIONS

Differences between ethnic groups in use of cardiovascular procedures narrowed markedly once a serious illness (ESRD) developed and adequate insurance coverage was ensured; the disparity was eliminated in patients with previous Medicare insurance or a stronger indication for a procedure. These findings suggest that almost equal access to care is attainable by combining insurance with delivery of comprehensive, clinically appropriate care.

Epidemiology of cardiovascular risk factors in chronic renal disease

Treatment and prevention of cardiovascular disease in the general population has benefited greatly from the identification of cardiovascular disease risk factors. Given the particularly high risk of cardiovascular disease and total mortality among patients with chronic renal insufficiency (CRI) and end-stage renal disease (ESRD), it is important to assess the role of traditional and nontraditional risk factors for cardiovascular disease. This review discusses the foundations of risk factor epidemiology and briefly summarizes the evidence regarding cardiovascular risk factors in renal disease. Diabetes and hypertension have a very high prevalence in patients with CRI. Patients with CRI and ESRD also have a higher frequency of cardiac dysfunction and left ventricular hypertrophy, which further increase the risk of cardiovascular disease. Finally, patients with renal disease have a higher prevalence of less established risk factors, including low HDL, and high triglycerides, lipoprotein(a), and homocysteine, where prospective studies and clinical trials are needed to provide a scientific basis for reduction of cardiovascular risk among patients with renal disease.

Serum creatinine levels in the US population: third National Health and Nutrition Examination Survey

This report describes the distribution of serum creatinine levels by sex, age, and ethnic group in a representative sample of the US population. Serum creatinine level was evaluated in the third National Health and Nutrition Examination Survey (NHANES III) in 18,723 participants aged 12 years and older who were examined between 1988 and 1994. Differences in mean serum creatinine levels were compared for subgroups defined by sex, age, and ethnicity (non-Hispanic white, non-Hispanic black, and Mexican-American). The mean serum creatinine value was 0.96 mg/dL for women in the United States and 1.16 mg/dL for men. Overall mean creatinine levels were highest in non-Hispanic blacks (women, 1.01 mg/dL; men, 1.25 mg/dL), lower in non-Hispanic whites (women, 0.97 mg/dL; men, 1.16 mg/dL), and lowest in Mexican-Americans (women, 0.86 mg/dL; men, 1.07 mg/dL). Mean serum creatinine levels increased with age among both men and women in all three ethnic groups, with total US mean levels ranging from 0.88 to 1.10 mg/dL in women and 1.00 to 1.29 mg/dL in men. The highest mean creatinine level was seen in non-Hispanic black men aged 60+ years. In the total US population, creatinine levels of 1.5 mg/dL or greater were seen in 9.74% of men and 1.78% of women. Overall, among the US noninstitutionalized population, 10.9 million people are estimated to have creatinine values of 1.5 mg/dL or greater, 3.0 million have values of 1.7 mg/dL or greater, and 0.8 million have serum creatinine levels of 2.0 mg/dL or greater. Mean serum creatinine values are higher in men, non-Hispanic blacks, and older persons and are lower in Mexican-Americans. In the absence of information on glomerular filtration rate (GFR) or lean body mass, it is not clear to what extent the variability by sex, ethnicity, and age reflects normal physiological differences rather than the presence of kidney disease. Until this information is known, the use of a single cutpoint to define elevated serum creatinine values may be misleading.

Creatinine clearance as a measure of GFR in screenees for the African-American Study of Kidney Disease and Hypertension pilot study

Serum creatinine and endogenous creatinine clearance (CrCl) are widely used measures of renal function. This study compares the precision, bias, and sources of error in using different CrCl measures to estimate the glomerular filtration rate (GFR) in 118 men and women screened for the African-American Study of Kidney Disease and Hypertension (AASK) pilot study. We measured serum creatinine, 24-hour CrCl, and CrCl during timed clearance periods conducted simultaneously with an 125I-iothalamate GFR study. Serum creatinine was measured using two different kinetic rate Jaffe methods (CX3 and Hitachi). After standardization for body surface area, the different measures of renal function available for each individual were compared with the 125I-iothalamate GFR simultaneous to the CrCl. In a subset of 50 participants, the CrCl measures were compared with a follow-up GFR (fGFR). The mean 125I-iothalamate GFR was 65.2 (SD, 26.4), with a range of 11 to 122 mL/min/1.73 m2. The mean +/- SD percentage differences from the GFR were -9%+/-22% for the Cockcroft-Gault estimated CrCl, 1%+/-29% for the 24-hour CrCl, and 8%+/-16% for the CX3 simultaneous CrCl. The Hitachi method overestimated serum creatinine and underestimated GFR. Compared with an fGFR, the mean +/- SD differences were 2%+/-19% for the first GFR, -6%+/-20% for the Cockcroft-Gault estimated CrCl, 10%+/-28% for the 24-hour CrCl, and 14%+/-29% for the CX3 simultaneous CrCl. Thus, the increased precision with which the timed CrCl predicted its simultaneous GFR did not extend to improved ability to predict a future GFR. The fractional excretion of creatinine, measured as the ratio of the CX3 simultaneous CrCl to 125I-iothalamate clearance, increased with decreasing GFR but was lower than expected (mean +/- SD of 1.21+/-0.16 for GFRs between 20 and 40 mL/min/1.73 m2). The lower fractional excretion explains why the 24-hour and Cockcroft-Gault CrCls did not overestimate GFR, but the reasons for this lower excretion are uncertain. Creatinine assay specificity and calibration are important sources of variability that must be examined in any CrCl measure of GFR. We conclude that despite requiring substantially more time and effort, neither the outpatient 24-hour urine nor the timed CrCl offered increased precision over a calculation based on serum creatinine, sex, age, and weight in predicting GFR.

Familial aggregation of renal disease in a population-based case-control study

Family history of renal disease has been associated with an increased risk of end-stage renal disease (ESRD). It is uncertain whether this risk is mediated by familial aggregation of risk factors for ESRD, such as diabetes and hypertension. The association of ESRD with familial aggregation of renal disease was examined in a large, population-based case-control study conducted in Maryland, Virginia, West Virginia, and Washington, DC. The number of first-degree relatives who were affected with any type of renal disease was compared between 689 newly treated ESRD patients registered in the Medicare ESRD program (92% of all eligible incident cases presenting between January and July of 1991) and 361 control subjects without ESRD who were selected by random-digit dialing (90% response rate). Patients and control subjects were frequency matched by age; patients with ESRD caused by polycystic kidney disease and other known hereditary kidney diseases were excluded. Analysis was conducted using multiple logistic regression. After controlling for the proband's age, gender, race, family size, socioeconomic status, and personal and family histories of diabetes and hypertension, having one first-degree relative with renal disease increased the odds of ESRD by 1.3 (95% confidence interval, 0.7 to 2.6) and having two or more affected first-degree relatives increased the odds of ESRD by 10.4 (95% confidence interval, 2.7 to 40.2). These data support familial aggregation of renal disease in excess of that predicted by clustering of diabetes and hypertension within families, suggesting that either genetic susceptibility or environmental exposures shared within families increase the risk of developing ESRD. This risk is also much higher when two or more first-degree relatives have renal disease. Unraveling the molecular basis of this increase in risk may provide new avenues for treatment and prevention of ESRD.

Further trends in the etiology of end-stage renal disease in African-Americans

Publications in the past year have continued to shed light on the etiology of the excess risk of end-stage renal disease end-stage renal disease among African-Americans. Prospective data now show that even mild elevations in blood pressure are associated with an increased risk of end-stage renal disease. The prevalence of hypertension among African-Americans has been declining, but remains much higher than among White people. Management of hypertension is the best avenue to prevent much of the excess burden of end-stage renal disease, but the relative merits of different agents and levels of blood pressure control are still under study. In addition, individuals with human immunodeficiency virus-related end-stage renal disease represent a small but rapidly growing number of patients that are predominantly African-American. Studies are underway to examine ethnic differences and risk factors for the earlier stages of renal disease as well as genetic mutations for non-Mendelian forms of end-stage renal disease.