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.     

Prevalence of low glomerular filtration rate in nondiabetic Americans: Third National Health and Nutrition Examination Survey (NHANES III)

End-stage renal disease is an important and costly health problem. Strategies for its prevention are urgently needed. Knowledge of the population-based prevalence of renal insufficiency in nondiabetic adults would inform such strategies. Black and white nondiabetic adult participants in the Third National Health and Nutrition Examination Survey were analyzed. The analysis was stratified by age, gender, and race, and four clinically applicable methods were used to assess renal function. There were 13,251 complete records for analysis. By the Modification of Diet in Renal Diseases (MDRD) GFR (GFR) prediction Equation 7, 58% (95% confidence interval [CI], 56 to 60%) of the total adult nondiabetic black and white US population had MDRD GFR below 80 ml/min per 1.73m(2), 13% (95% CI, 11 to 14%) below 60 ml/min per 1.73m(2), and 0.26% (95% CI, 0.19 to 0.33%) below 30 ml/min per 1.73m(2). By the Cockcroft-Gault formula, the equivalent figures were 39% (95% CI, 37 to 41%), 14% (95% CI, 12% - 16%), and 0.81% (95% CI, 0.46 to 1.2%), respectively. The findings of an unexpectedly high prevalence of low clearance and the increased prevalence of low clearance with age were consistent across the four clearance estimation methods used and for each race-sex stratum. The absolute magnitude of the prevalence of low clearance was, however, dependent on the clearance method used. Assessed by estimation from serum creatinine, low clearance may be very common, particularly with advancing age. The prognosis (in terms of risk for progression and end-stage renal disease) of low clearance in unreferred populations may differ from that in referred populations and requires further study.     

Demographic, dietary, and serum factors and parathyroid hormone in the National Health and Nutrition Examination Survey

Summary

Many determinants of parathyroid hormone (PTH) are unknown. In the National Health and Nutrition Examination Survey (NHANES), numerous factors not classically associated with calcium–phosphorus homeostasis, such as uric acid and smoking, are independently associated with PTH in adults without chronic kidney disease. Associations between serum phosphorus and PTH may vary by race.

Introduction

Although PTH may be an important biomarker for osteoporosis and cardiovascular disease, many determinants of PTH are unknown. We investigated associations between demographic, dietary, and serum factors and PTH level.

Methods

We studied 4,026 white, 1,792 black, and 1,834 Mexican-American adult participants without chronic kidney disease from the 2003–2004 and 2005–2006 NHANES.

Results

The mean serum PTH level was 38.3?pg/ml for whites, 42.6?pg/ml for blacks, and 41.3?pg/ml for Mexican-Americans. After adjusting for diet, body mass index, serum levels of calcium, phosphorus, 25-hydroxyvitamin D, creatinine, and other factors, smokers compared to non-smokers had lower PTH, ranging from ?4.2?pg/ml (95% confidence interval (CI) ?7.3 to ?1.1) in Mexican-Americans to ?6.1?pg/ml (95% CI ?8.7 to ?3.5) in blacks. After multivariate adjustment, PTH was higher in females compared to males, ranging from 1.1?pg/ml (95% CI ?1.2 to 3.4) in Mexican-Americans to 4.5?pg/ml (95% CI 1.9 to 7.0) in blacks, and in older (>60?years) compared to younger participants (<30?years), ranging from 3.7?pg/ml (95% CI 1.3 to 6.1) in Mexican-Americans to 8.0?pg/ml (95% CI 5.4 to 10.7) in blacks. Higher uric acid was associated with higher PTH. In whites only, lower serum phosphorus and lower serum retinol were associated with higher PTH.

Conclusions

Numerous factors not classically associated with calcium–phosphorus homeostasis are independently associated with PTH and should be considered in future studies of PTH and chronic disease. Additional research is needed to elucidate mechanisms underlying identified associations with PTH and to explore possible racial differences in phosphorus handling.     

25-Hydroxyvitamin D, insulin resistance, and kidney function in the Third National Health and Nutrition Examination Survey

Previous research has reported reduced serum 25-hydroxyvitamin D levels in patients with chronic kidney disease (CKD), although the relationship between vitamin D status and insulin resistance (IR) in patients with CKD has not been examined in the general population. We examined the association that kidney function, based on glomerular filtration rate (eGFR) estimated from serum creatinine, has with serum levels of 25-hydroxyvitamin D and components of the metabolic syndrome among 14 679 participants in the Third National Health and Nutrition Examination Survey (NHANES III). In this analysis, adjusted mean serum 25-hydroxyvitamin D was significantly lower only in the participants with a severe (15-29 ml/min/1.73 m(2)) decrease in eGFR compared to those with normal kidney function (61.6 vs 73.3 nmol/l, P=0.0063). Serum 25-hydroxyvitamnin D (P=0.0018) and level of kidney function (P=0.0003) were inversely associated, independent of each other, with homeostasis model assessment of insulin resistance (HOMA-IR), adjusting for confounders. Participants with high 25-hydroxyvitamin D levels (>81 nmol/l) had lower HOMA-IR. We conclude that 25-hydroxyvitamin D deficiency is not as prevalent in the US general population with decreased eGFR as previously reported in patients with CKD; and that vitamin D and kidney function have independent inverse associations with IR.     

The prevalence of urinary incontinence among community dwelling adult women: results from the National Health and Nutrition Examination Survey

PURPOSE: Population based studies estimate that a large proportion of adult women report urinary incontinence. However, there is a wide range of estimates of the burden posed by UI. To measure the prevalence of incontinence in women in the community we analyzed data from women responding to the National Health and Nutrition Examination Survey. MATERIALS AND METHODS: NHANES is a series of health and nutrition surveys performed by the National Center for Health Statistics. From 1999 to 2000 NHANES asked a national sample of community dwelling women, "In the past 12 months, have you had difficulty controlling your bladder, including leaking small amounts of urine when you cough or sneeze (exclusive of pregnancy or recovery from childbirth)?" Questionnaire results were recorded and analyzed with respect to demographic data including age, race and level of education. RESULTS: The overall prevalence of urinary incontinence in women was 38%. The prevalence of daily incontinence increased with age, ranging from 12.2% in women 60 to 64 years old to 20.9% in women 85 years old or older. Of women reporting any incontinence, 13.7% reported daily incontinence, and an additional 10.3% reported weekly incontinence. Prevalence was higher in non-Hispanic white women (41%) than in non-Hispanic black (20%) or Mexican-American women (36%). Women with less than a high school education were less likely to report incontinence than were those with at least a high school education. CONCLUSIONS: Unlike many other studies the NHANES draws a nationally representative sample of subjects in the community and, thus, provides prevalence data for urinary incontinence for all women in the United States. Prevalence is high, and varies with age, race/ethnicity and socioeconomic variables.     

Urinary cadmium levels predict lower lung function in current and former smokers: data from the Third National Health and Nutrition Examination Survey

BACKGROUND: A study was undertaken to determine the relation between urinary cadmium levels and lung function in a nationally representative cohort of current, former, and never smokers in the US. Urinary cadmium levels reflect the total body burden of cadmium. METHODS: The following data from the Third National Health and Nutrition Examination Survey were analysed: urinary cadmium (adjusted for urinary creatinine), lung function, sex, race/ethnicity, age, education level, job category, body mass index, serum cotinine level, and smoking history. Linear regression models were developed to predict lung function using urinary cadmium as the main predictor, adjusting for other covariates and stratified by smoking status. RESULTS: Data were available on 16 024 adults. Current smokers had higher mean (SE) urinary cadmium/creatinine levels (0.46 (0.01) micro g/g) than former (0.32 (0.01) micro g/g) or never smokers (0.23 (0.01) micro g/g). Higher levels of urinary cadmium were associated with significantly lower forced expiratory volumes in 1 second (FEV(1)) in current (-2.06%, 95% confidence interval (CI) -2.86 to -1.26 per 1 log increase in urinary cadmium) and former smokers (-1.95%, 95% CI -2.87 to -1.03) but not in never smokers (-0.18%, 95% CI -0.60 to 0.24). Similar results were obtained for forced vital capacity (FVC) and FEV(1)/FVC. CONCLUSIONS: Cadmium, which is known to cause emphysema in occupational settings, may also be important in the development of tobacco related lung disease.     

Association between low testosterone and anaemia: Analysis of the National Health and Nutrition Examination Survey

There is an androgen effect on haematopoiesis; however, the effect of low testosterone in anaemia has not been fully studied. In this study, we aim to explore the association of total serum testosterone, low testosterone (≤300 ng/dl), haemoglobin concentration and prevalence of anaemia in a nationally representative sample of men. We analysed data from the NHANES III database, and men between the age of 18–80 years of age were selected. We defined anaemia as haemoglobin ≤13.5 ng/dl and low serum testosterone as ≤300 ng/dl. After analysing 5,888 men, it was shown that those with anaemia had a higher prevalence of low serum testosterone (32.3%) compared to those without anaemia (24.1%) (p < .001), and in multivariable-adjusted analysis, it was shown that low testosterone was significantly associated with anaemia (OR = 1.44; 95% CI: 1.17–1.78; p = .001). Our findings suggest that men with low serum testosterone have a higher risk of anaemia, and there is a positive association between serum testosterone and serum Hb. Further prospective studies need to be performed to confirm our findings.     

Prostate-specific antigen levels in relation to cadmium exposure and zinc intake: results from the 2001-2002 National Health and Nutrition Examination Survey

BACKGROUND: Cadmium exposure has been suggested as a risk factor for prostate cancer, and experimental literature suggests that the carcinogenic effect of cadmium is modified by the presence of zinc. We evaluated total prostate-specific antigen (PSA) levels in relation to urinary cadmium concentrations and dietary zinc intake. METHODS: PSA levels were determined in 1,320 men over the age of 40 in the 2001-2002 National Health and Nutrition Examination Survey (NHANES). Urinary cadmium concentrations were measured in about one-third of the sample population, whereas dietary zinc intake was based on participants' 24-hr recall. Information on all three variables was available for 422 men in the 2001-2002 NHANES survey. We performed linear regressions to evaluate the relationships these factors after accounting for age and other covariates. RESULTS: Little evidence for an association between cadmium and elevated PSA level was observed. However, the data provide suggestive evidence for an interaction between zinc intake and cadmium exposure (P for interaction=0.09). Among men with zinc intake less than the median level of 12.67 mg/day, an increase in 1 microg/g creatinine cadmium exposure was associated with a 35% increase in PSA level. In contrast, among men with greater than median zinc intake, little evidence for an association between cadmium and PSA was found. CONCLUSIONS: These findings suggest a protective effect of zinc intake on cadmium-induced prostatic injury, and may provide further rationale for investigating the impact of these factors individually and jointly on the etiology of prostate cancer.     

Islet cell autoimmunity in a triethnic adult population of the Third National Health and Nutrition Examination Survey

Markers of humoral islet cell autoimmunity, such as autoantibodies (AAs) against the 65-kDa isoform of GAD (GAD65), serve as determinants of risk for autoimmune diabetes. Despite the high prevalence of diabetes in U.S. racial and ethnic minority adult populations, little is known concerning the prevalence of GAD65 AA in these groups. We estimated the prevalence of GAD65 AA in 1,064 diabetic and 1,036 nondiabetic participants who were 40-90 years of age from the Third National Health and Nutrition Examination Survey (NHANES III), which provides a representative ethnic sample of the U.S. diabetic population. The prevalence of GAD65 AA was higher in diabetic participants compared with nondiabetic participants in non-Hispanic whites (n = 920; 6.3% vs. 2.0%; P = 0.001) and non-Hispanic blacks (n = 534; 3.7% vs. 1.3%; P = 0.08) but not in Mexican Americans (n = 646; 1.2% vs. 2.6%; P = 0.18). Among diabetic non-Hispanic whites and non-Hispanic blacks, being GAD65 AA positive was associated with lower BMI and C-peptide (P < 0.05). These results may reflect the outcome of an autoimmune process leading to beta-cell destruction/dysfunction in non-Hispanic white and non-Hispanic black adult diabetic patients as it occurs in a similar manner in type 1 diabetes. Among diabetic Mexican Americans, the lower prevalence of GAD65 AA suggests a lower frequency of autoimmune-related diabetes.     

Racial differences in the relationship between vitamin D, bone mineral density, and parathyroid hormone in the National Health and Nutrition Examination Survey

Summary  

It is unclear whether optimal levels of 25-hydroxyvitamin D (25(OH)D) in whites are the same as in minorities. In adult participants of NHANES, the relationships between 25(OH)D, bone mineral density (BMD), and parathyroid hormone (PTH) differed in blacks as compared to whites and Mexican-Americans, suggesting that optimal 25(OH)D levels for bone and mineral metabolism may differ by race.