Five-year intra-individual variability in C-reactive protein levels in a Japanese population-based study: the Jichi Medical School Cohort Study at Yamato, 1993-1998

Four-year stability of anthropometric and cardio-metabolic parameters in a prospective cohort of older adults

AIM

To examine the medium-term stability of anthropometric and cardio-metabolic parameters in the general population.

MATERIALS & METHODS

Participants were 5160 men and women from the English Longitudinal Study of Ageing (age ≥50 years) assessed in 2004 and 2008. Anthropometric data included height, weight, BMI and waist circumference. Cardio-metabolic parameters included blood pressure, serum lipids (total cholesterol, HDL, LDL, triglycerides), hemoglobin, fasting glucose, fibrinogen and C-reactive protein.

RESULTS

Stability of anthropometric variables was high (all intraclass correlations >0.92), although mean values changed slightly (-0.01 kg weight, +1.33 cm waist). Cardio-metabolic parameters showed more variation: correlations ranged from 0.43 (glucose) to 0.81 (HDL). The majority of participants (71-97%) remained in the same grouping relative to established clinical cut-offs.

CONCLUSION

Over a 4-year period, anthropometric and cardio-metabolic parameters showed good stability. These findings suggest that when no means to obtain more recent data exist, a one-time sample will give a reasonable approximation to average levels over the medium-term, although reliability is reduced.

Intraindividual variability over time in plasma biomarkers of inflammation and effects of long-term storage

PURPOSE

Systemic measures of chronic inflammation, often based on a single blood draw, are frequently used to study the associations between inflammation and chronic diseases such as cancer. However, more information is needed on the measurement error in these markers due to laboratory error, within-person variation over time, and long-term storage.

METHODS

We investigated the intraindividual variability of inflammation markers C-reactive protein (CRP), interleukin-6 (IL-6), and soluble tumor necrosis factor receptors I and II (sTNFRI and II) in a subsample of the Seattle Barrett's esophagus study cohort. Two fasting blood samples were collected between 1995 and 2009 from 360 participants on average 1.8 years apart. CRP, IL-6, and sTNF receptor levels were measured by immunonephelometry, ELISA, and multiplex assays, respectively. Intra- and inter-batch coefficients of variation (CV) were estimated using blinded pooled samples within each batch. Intraclass correlations (ICCs) were computed using random effects ANOVA.

RESULTS

Intra- and inter-batch CVs for the pooled plasma aliquots were low (2.4-8.9 %), suggesting little laboratory variability. Reliability over time was excellent for sTNF receptors (ICCsTNF-RI = 0.89, ICCsTNF-RII = 0.85) and fair-to-good for CRP and IL-6 (ICCCRP = 0.55, ICCIL-6 = 0.57). For samples stored for over 13 years, the ICCs for CRP and IL-6 were decreased but those for sTNF receptors were unaffected.

CONCLUSION

sTNF receptor levels are more stable within person over time than CRP or IL-6. Long-term storage of samples appears to increase the variability of CRP and IL-6 measures, while the reliability of soluble TNF receptor measures was not affected by storage time.

Long-term variability of inflammatory markers and associated factors in a population-based cohort

OBJECTIVES

To investigate long-term variability in serum high-sensitivity C-reactive protein (CRP) and interleukin-6 (IL-6) and to determine associated risk factors for high-risk inflammatory profiles.

DESIGN

Prospective population-based cohort study.

PARTICIPANTS

Participants (N = 1,443) of the Epidemiology of Hearing Loss Study and the Beaver Dam Eye Study, two population-based prospective studies of aging in the same cohort.

MEASUREMENTS

In participants aged 43 to 79 at the initial examination (1988-1990), serum high-sensitivity CRP was measured from three time-points (1988-1990, 1998-2000, 2009-2010), and serum IL-6 was measured from two (1998-2000, 2009-2010).

RESULTS

When IL-6 levels were categorized into tertiles, 50.8% of participants were in the same group 10 years later (weighted kappa (κ) = 0.34). When CRP was categorized into three risk groups, 53.4% of participants were in the same group 10 years later (κ = 0.36), and 32.4% were in the same group at all three examinations (κ = 0.27). IL-6 increased from a geometric mean of 1.54 pg/L to 1.78 pg/L over 10 years, whereas CRP increased from a geometric mean of 1.67 mg/L to 2.25 mg/L over 10 years and then decreased to 1.93 mg/L over the next 10 years. These 10-year decreases in CRP were not observed in those not reporting statin use. Factors associated with long-term higher levels of IL-6 and CRP were older age (IL-6), obesity, smoking, lower physical activity (IL-6), lower high-density lipoprotein cholesterol (IL-6), and a history of statin (non)use (CRP).

CONCLUSION

Inflammatory marker levels tracked over the long term into older age with within-person increases were observed. Several potentially modifiable risk factors were associated with long-term higher levels of inflammatory markers.

Intraindividual variability of C-reactive protein: the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

The intraindividual variability of C-reactive protein (CRP) remains uncertain. Although guidelines suggest stability of serial CRP values comparable to that of cholesterol measures, several studies indicate greater fluctuations of CRP. We sought to compare the intraindividual variability of CRP with that of cholesterol measures using the multi-ethnic study of atherosclerosis (MESA).

METHODS

CRP measurements were available in 760 MESA participants after exclusion of those with comorbidities or medications known to affect CRP or CRP≥10 mg/L. Serial values were available for 255 participants. The intraclass correlation coefficient (ICC) was quantified for CRP, total cholesterol (TC), and non-HDL-cholesterol (non-HDL-C) as the ratio of between-subject variance to the sum of between-subject and within-subject variance. Fluctuation between baseline and follow-up categories was calculated by cross-classifying participants according to baseline tertiles.

RESULTS

The multivariable-adjusted ICC of CRP was 0.62 (95% CI, 0.55-0.68), significantly lower than that of TC (0.75; 95% CI, 0.70-0.81; p = 0.001 vs CRP) and non-HDL-C (0.76; 95% CI, 0.71-0.81; p = 0.001 vs CRP). 51% of participants in the highest baseline CRP tertile had discordant values on follow-up, while 54% and 27% were discordant in the middle and lowest baseline CRP tertiles. Among participants with baseline CRP levels exceeding 3 mg/L, a clinical threshold for higher risk, 69% had subsequent measurements falling within a lower risk category.

CONCLUSIONS

In the MESA cohort, intraindividual variation of CRP was significantly greater than that for cholesterol measures. Our results suggest that further evaluation of CRP variability is needed in large prospective studies using shorter intervals between measurements.

Reliability of serum biomarkers of inflammation from repeated measures in healthy individuals

BACKGROUND

Biomarkers of low-grade systemic inflammation are used to study the associations of inflammation with chronic diseases, including cancer. However, relatively little is known about the intraindividual variability of most of these measures.

METHODS

Fasting serum samples, collected at baseline and the end of ≥3-week washout periods in a four-diet crossover feeding trial, were used to measure the inflammatory markers high sensitivity C-reactive protein (hsCRP), interleukin (IL)-6, tumor necrosis factor (TNF)-α, IL-8, and soluble TNF receptor (sTNFR) I and II. Participants included 62 men and women for analyses of IL-6 and CRP and 56 for analyses of IL-8, TNF-α, and sTNFRs, aged 20 to 40, who were free of factors known to influence inflammation, for example, chronic disease, medication use, heavy alcohol use, smoking, and obesity (body mass index >30 kg/m(2)). Intraclass correlations (ICC) were estimated using random effects ANOVA, across all four time points (~6 weeks apart).

RESULTS

ICCs for TNF-α and sTNFR I and II were very high: ICC = 0.92 [95% confidence interval (CI), 0.89-0.96], 0.92 (95% CI, 0.88-0.95), and 0.90 (95% CI, 0.85-0.94), respectively. ICCs for IL-8 and hsCRP were 0.73 (95% CI, 0.63-0.83) and 0.62 (95% CI, 0.49-0.75), respectively. The ICC for IL-6 was considerably lower, ICC = 0.48 (95% CI, 0.36-0.62). Three measures of IL-6 would be needed to achieve a reliability coefficient (Cronbach α) of 0.75.

CONCLUSIONS

With the exception of IL-6, reliability of all inflammatory markers in our panel was high.

IMPACT

This suggests that a single measure accurately captures the short-term (e.g., 4-6 months) variability within an individual.

Reproducibility of high-sensitivity C-reactive protein as an inflammatory component of metabolic syndrome in Japanese

BACKGROUND

Cutoff points for high-sensitivity C-reactive protein (hs-CRP) as a component of metabolic syndrome (MetS) in Japanese have been proposed as 0.40-0.45 mg/L for men and 0.25-0.35 mg/L for women. However, there are some concerns about the reproducibility of hs-CRP.

METHODS AND RESULTS

Reproducibility of hs-CRP as a component of MetS was examined using receiver-operating characteristic (ROC) curves for diagnosing MetS in 1,274 men and 673 women whose serum levels of hs-CRP were measured twice at annual health screening tests. The Spearman's correlation coefficient between baseline hs-CRP and hs-CRP at the next year's test was 0.68 in men and 0.71 in women. The area under the ROC curves of baseline hs-CRP, hs-CRP at the next year's test, and the mean of the 2 hs-CRP tests for diagnosing baseline MetS were 0.71, 0.71, and 0.72, respectively, in men and 0.75, 0.74, and 0.74, respectively, in women. Optimal cutoff points of baseline hs-CRP, hs-CRP at the next year's test, and the mean of 2 tests for diagnosing baseline MetS were all 0.40 mg/L in men and 0.35 mg/L in women.

CONCLUSIONS

The serum level of hs-CRP was stable enough for use as a measure of the inflammatory component of MetS, and the optimal cutoff point of hs-CRP was 0.40 mg/L for men and 0.35 mg/L for women in a Japanese health-screening population.

Intra-individual variation in serum C-reactive protein over 4 years: an implication for epidemiologic studies

BACKGROUND

Data on long-term intra-individual variability in high-sensitivity C-reactive protein (hsCRP) are needed to determine whether one measurement adequately reflects usual levels in prospective studies of on the etiology of cancer and other chronic diseases; when not reflective, the ability to statistically detect modest to moderate associations is reduced. The authors estimated the size of this source of variability and consequent attenuation of the relative risk (RR).

METHODS

High-sensitivity C-reactive protein (hsCRP) concentration was measured using a high-sensitivity immunoturbidometric assay in sera collected at years 2, 4, and 6 from 50 men in the placebo arm of the Prostate Cancer Prevention Trial (PCPT). After natural logarithm-transformation of hsCRP, analysis of variance was used to estimate the within- and between-individual variances from which the intra-class correlation coefficient (ICC) was calculated.

RESULTS

The observed RR due to an ICC < 1 was calculated by e((ln true RR*ICC)) for a range of true RRs. The 4-year ICC was 0.66. Measuring hsCRP once and assuming no other error, if the true RRs were 1.50, 2.00, and 3.00 when comparing high with low concentration, then the observed RRs would be 1.31, 1.58, and 2.06, respectively.

CONCLUSION

Investigators planning to measure hsCRP only once should design adequately sized studies to preserve inferences for hypothesized modest to moderate RRs.

Lifecourse socioeconomic trajectories and C-reactive protein levels in young adults: findings from a Brazilian birth cohort

Socioeconomic factors are associated with cardiovascular disease. C-reactive protein (CRP) is increasingly implicated as a candidate linking conventional risk factors and atherosclerosis. The impact of early- and later-life socioeconomic status (SES) on CRP levels has not been widely investigated and a handful of studies from high-income countries are inconsistent. We set out to examine the associations between lifecourse socioeconomic indicators (family income at birth, maternal education, family income at age 23 and own education) on CRP levels in young adults belonging to the 1982 Pelotas (Brazil) Birth Cohort Study (n = 5914). Early-life SES showed significant and graded associations with CRP levels at age 23 independently of later SES. For example, men with higher family income at birth showed higher CRP levels at age 23 (p = 0.001 for trend) and women with less educated mothers showed higher CRP levels (p = 0.01 for trend). Notably, differential directions of association between SES indicators and CRP levels between men and women were found. When adjusted for SES at age 23, men with the lowest family income at birth showed 42% lower CRP levels when compared to men in the highest family income group (−42; 95% CI: -60,-16). In contrast women born to the least educated mothers had the highest CRP levels (35; 95% CI -2, 86). In both sexes, adiposity accounted for the overwhelming majority of the associations between SES and CRP levels. Sex and gender roles specific to middle-income countries, socio-cultural and environmental conditions that may impact adiposity, and the level of epidemiological transition may be key factors that are linked to the associations between lifecourse SES and CRP levels. Public health strategies aimed at decreasing the burden of cardiovascular disease in middle-income settings, in addition to highlighting the risks associated with adult obesity, should not overlook the wide-ranging impacts of lifecourse social determinants.

High-sensitivity C-reactive protein and lipoprotein-associated phospholipase A2 stability before and after stroke and myocardial infarction

BACKGROUND AND PURPOSE

High-sensitivity C-reactive protein (hsCRP) and lipoprotein-associated phospholipase A2 (Lp-PLA2) are hypothesized to be biomarkers of systemic inflammation and risk of myocardial infarction (MI) and stroke. Little is known, however, about the stability of these markers over time, and in particular, about the effects of acute vascular events on these marker levels.

METHODS

Serum samples were collected at 4 annual intervals in 52 stroke-free participants from the Northern Manhattan Study (NOMAS) and assayed for hsCRP and Lp-PLA2 mass and activity levels using standard techniques. Log transformation of levels was performed as needed to stabilize the variance. Stability of marker levels over time was assessed using random effects models unadjusted and adjusted for demographics and other risk factors. In addition, samples from 37 initially stroke-free participants with stroke (n=17) or MI (n=20) were available for measurement before and after the vascular event (median 5 days, range 2 to 40 days). Levels before and after events were compared using nonparametric tests.

RESULTS

HsCRP and Lp-PLA2 activity levels were stable over time, whereas Lp-PLA2 mass levels decreased on average 5% per year (P=0.0015). Using accepted thresholds to define risk categories of Lp-PLA2 mass, there was no significant change over time. HsCRP increased after stroke (from median 2.2 mg/L prestroke to 6.5 mg/L poststroke; P=0.0067) and MI (from median 2.5 mg/L pre-MI to 13.5 mg/L post-MI; P<0.0001). Lp-PLA2 mass and activity levels both decreased significantly after stroke and MI (for Lp-PLA2 mass, from median 210.0 ng/mL to 169.4 ng/mL poststroke, P=0.0348, and from median 233.0 ng/mL to 153.9 post-MI, P<0.0001).

CONCLUSION

Lp-PLA2 mass levels decrease modestly, whereas hsCRP and Lp-PLA2 activity appear stable over time. Acutely after stroke and MI, hsCRP increases whereas Lp-PLA2 mass and activity levels decrease. These changes imply that measurements made soon after stroke and MI are not reflective of prestroke levels and may be less reliable for long-term risk stratification.

Very low levels of high-sensitivity C-reactive protein are not bimodally distributed but are significantly related to other metabolic risk factors in Japanese

BACKGROUND

High-sensitivity C-reactive protein (hs-CRP) is an independent risk factor of diabetes and cardiovascular disease and it is proposed as a component of metabolic syndrome. Blood levels of hs-CRP are reported to be much lower in Japanese than in Westerners and bimodally distributed in Japanese.

METHODS

Very low levels of hs-CRP were examined using medical check-up data of 1,360 Japanese men and 821 women whose plasma levels of high-sensitivity C-reactive protein (hs-CRP) were below 10 mg/L.

RESULTS

The distribution of hs-CRP levels were skewed but not bimodal in both men and women and very low levels of hs-CRP were significantly related to waist circumference, systolic blood pressure, diastolic blood pressure, fasting glucose, triglycerides, and low-density lipoprotein cholesterol in both men and women. The area under receiver operating characteristic curve of hs-CRP for diagnosing metabolic syndrome and Spearman's correlation coefficients between hs-CRP and components of metabolic syndrome were comparable to those of components of metabolic syndrome in both men and women.

CONCLUSION

Very low levels of hs-CRP were not bimodally distributed but were significantly related to metabolic risk factors in Japanese.

Long-term C-reactive protein variability and prediction of metabolic risk

OBJECTIVE

This analysis was undertaken to determine the long-term intraindividual variability, determinants of change, and capacity of the inflammatory marker C-reactive protein (CRP) to predict metabolic traits and diabetes in a large community-based population.

METHODS

Intraindividual CRP variability, predictors of CRP change, and metabolic events were evaluated in the Framingham Heart Study Offspring cohort using data from the same 2409 participants with CRP measured by the same methodology at each of 3 examination cycles, spanning 20 years.

RESULTS

Between the first and second examinations (averaging 16 years apart), 23% to 47% of men and 27% to 49% of women remained within the same quintile of CRP values. An additional 24% to 51% of men and 24% to 50% of women occupied an adjacent quintile. Intermediate-term CRP variability (over 4 years) was similar to long-term variability. Both long- and intermediate-term variability of CRP were significantly less than that of plasma cholesterol measured in these same groups. Linear regression models for CRP at the intermediate examination demonstrated that CRP at the initial examination contributed the largest proportion of the variability (partial R-square = 0.27) seen in the overall model after adjustment for other covariates known to affect CRP concentrations. Although logistic regression models demonstrated that CRP over the intermediate term did not predict new-onset metabolic syndrome at the final examination, CRP did predict an increase in glucose and new-onset diabetes.

CONCLUSION

The results of this longitudinal analysis suggest the intraindividual, long-term variability of CRP concentrations is relatively small and predictive of new diabetes over an intermediate-term of 4 years.

Considerable disagreement among definitions of metabolic syndrome for Japanese

BACKGROUND

The purpose of the present study is to examine the agreement of various existing definitions of metabolic syndrome for Japanese.

METHODS AND RESULTS

One hundred thirty-two apparently healthy men and 147 apparently healthy women underwent testing and diagnosis for metabolic syndrome using 5 different definitions of metabolic syndrome for Japanese, including a newly proposed definition: a modified National Cholesterol Education Program definition replacing abdominal obesity with C-reactive protein. The agreement of these various definitions of metabolic syndrome was studied using an agreement index defined as the number of subjects who met both definitions divided by the number of subjects who met either of the 2 definitions. Agreement indices among these various definitions of metabolic syndrome for Japanese were between 0.19 and 0.6 in men and between 0.31 and 0.89 in women. The average agreement index was 0.41 in men and 0.51 in women, and the overall agreement index was 0.15 in men and 0.21 in women.

CONCLUSIONS

There was considerable disagreement among various definitions of metabolic syndrome for Japanese. Therefore, diagnosis with this syndrome should not be made until a truly consensual definition of metabolic syndrome can be established.

Comparison of C-reactive protein levels between serum and plasma samples on long-term frozen storage after a 13.8 year interval: the JMS Cohort Study

BACKGROUND

C-reactive protein (CRP) is an acute phase reactant, and has been reported as a predictor of cardiovascular diseases. Measurements of high sensitive CRP in thawed samples are possible and the values are thought to remain stable even after frozen storage. However, the long-term stability of CRP values has not been documented. We measured the values of CRP before and after long-term storage, and examined the difference in determined values.

METHODS

High sensitive CRP was measured before and after long-term storage of samples from 99 men and women among the JMS Cohort Study subjects. We selected subjects who underwent measurement of high sensitive CRP at the baseline by stratified sampling methods using baseline CRP values. CRP was measured in serum samples at the baseline and in thawed plasma samples after an average storage period of 13.8 years.

RESULTS

Geometric means of CRP were 0.25 mg/L and 0.59 mg/L before and after storage, respectively. The CRP values were significantly higher after long-term frozen storage than at the baseline (p<0.0001). The both values of logarithm CRP were significantly correlated using Pearson's correlation (r = 0.920, 95% confidence interval: 0.883-0.945).

CONCLUSION

CRP values increased after long-term frozen storage. The CRP values showed a high correlation between before and after long-term storage.

Stability of soluble adhesion molecules, selectins, and C-reactive protein at various temperatures: implications for epidemiological and large-scale clinical studies

BACKGROUND

We assessed the impact of sample storage conditions on soluble vascular cell adhesion molecules (sVCAM), soluble intracellular adhesion molecules (sICAM-1), soluble (s)E-selectin, C-reactive protein (CRP), and sP-selectin.

METHODS

Markers were measured by ELISA in venous blood from 10 healthy volunteers on aliquots stored as plasma or whole blood at 4, 21, or 30 degrees C for 1-5 days and after 1-5 freeze-thaw cycles. We compared results on these samples to results for samples processed immediately and stored at -80 degrees C. Statistical models assessed time-related effects and effects of postprocessing conditions.

RESULTS

Using an upper limit of 10% variation from baseline with P >0.05, we found that stability duration in plasma was 5 days for sVCAM-1 and sICAM-1 and at least 2 days for sE-selectin at 4, 21, and 30 degrees C and 5 days for CRP at 4 and 21 degrees C and 1 day at 30 degrees C. Stability duration in whole blood was 5 days for sVCAM-1 and sICAM-1 and at least 2 days for sE-selectin at 4, 21, and 30 degrees C and 5 days for CRP at 4 and 21 degrees C and 2 days at 30 degrees C. sP-selectin was not stable in plasma or whole blood. sICAM-1, sVCAM-1, CRP, and sE-selectin were stable after 5 freeze-thaw cycles.

CONCLUSIONS

sVCAM-1, sICAM-1, and CRP are stable in plasma or whole blood at 4 and 21 degrees C for at least 3 days and sE-selectin for 2 days. sP-selectin is not stable and therefore requires immediate assay.

Childhood C-reactive protein in predicting CRP and carotid intima-media thickness in adulthood: the Cardiovascular Risk in Young Finns Study

BACKGROUND

Atherosclerosis begins in childhood, and inflammation may contribute to its pathophysiology. The value of measuring inflammatory markers in the pediatric risk assessment, however, is uncertain. We examined whether childhood C-reactive protein (CRP) levels predict CRP and carotid intima-media thickness (IMT) in adulthood.

METHODS AND RESULTS

Study cohort included 1617 subjects, aged 3 to 18 years at baseline in 1980. These subjects were reexamined in 2001 at ages 24 to 39 years. In 2001, CRP was measured from fresh samples, and the subjects underwent carotid IMT study to evaluate subclinical atherosclerosis. Baseline (1980) CRP concentrations were measured from frozen samples in 2005. A significant tracking was observed between childhood and adult CRP levels. The age- and sex-specific correlations were the highest in the age group of 18 years at baseline (r=0.47 in females, r=0.32 in males, P<0.0001). The association between childhood and adult CRP levels was independent of serum lipids, blood pressure, smoking, obesity indices, and insulin. In multivariate analysis, childhood risk factors that independently associated with increased adult IMT included elevated systolic blood pressure (P<0.0001), high low-density lipoprotein-cholesterol (P=0.01) and smoking (P=0.049), but not CRP (P=0.95).

CONCLUSIONS

Childhood CRP values predict weakly but significantly adult CRP, and this association is independent of other metabolic risk factors. Unlike conventional risk factors, however, childhood CRP does not predict adult IMT.

Intra-Individual Variability of High-Sensitivity C-Reactive Protein Age-Related Variation Over Time in Japanese Subjects

BACKGROUND

Prospective studies have demonstrated a direct association between the baseline level of high-sensitivity C-reactive protein (hsCRP) and the risk of developing cardiovascular disease. The potential for hsCRP variability during the follow-up interval is of great interest, so the repeatability of measurements of hsCRP in men and women, and in different age groups, was investigated in the present study.

METHODS AND RESULTS

The measurement of hsCRP was performed in 899 male and 780 female Japanese civil servants aged 18-60 years in the spring of 2004 and 2005. Within-subject repeatability and intra-class correlation coefficient of reliability were used to characterize the variation in measurements. Error of the measurement process was negligible, as the analytical variance was 0.0003 [ln(mg/L)] [ln(mg/L)] with a reliability coefficient of 0.997. In contrast, the within-subject variation of hsCRP was considerable with a reliability coefficient of 0.61 in both sexes and repeatability coefficients of 5.25 and 5.38 in men and women, respectively. The variation differed with age, especially in women, as less variation was observed in subjects over 40 years of age during the follow-up interval.

CONCLUSIONS

The results suggest that a single measurement of hsCRP is subject to considerable but equal within-subject variation over time in men and women, and this variation differs among the age groups, which may affect the risk assessment of hsCRP in association with future cardiovascular events.

Five-year stability of job characteristics scale scores among a Japanese working population

BACKGROUND: The job characteristics scale of job strain, which combines high job demands and low decision latitude based on Karasek’s model, has been applied to studies on health care and cardiovascular disease. However, little is known about the long-term stability of this scale with exposure of workers to job. We investigated the 5-year intraindividual variation in job characteristics scores among healthy community workers.

METHODS: Subjects of the study were 458 community dwelling persons forming part of the Jich Medical School Cohort Study at Yamato (currently, Minami-Uonuma city), Niigata prefecture. The Japanese version of the World Health Organization Multinational Monitoring of Trends and Determinants in Cardiovascular Disease (WHO-MONICA) Psychosocial Study Questionnaire was implemented twice (from 1992 through 1995, and in 1999) to measure job demands and decision latitude levels. Intraclass correlation coefficients were computed to evaluate stability of scores of the questionnaire.

RESULTS: Intraclass correlation coefficient of the decision latitude scores was 0.629 (95% confidence interval: 0.564 - 0.686) and that of the job demands scores was 0.551 (0.476 - 0.617). Subgroup analyses by age, sex, education level, years since first employment, number of co-workers, and job category and status at baseline revealed similar results. In contrast, subjects who experienced position changes within the same enterprise or changed jobs showed lower correlation coefficients of both decision latitude and job demands scores compared to those who experienced no change in job contents.

CONCLUSION: The Japanese version of the WHO-MONICA Psychosocial Study Questionnaire showed statistically significant long-term stability and could be to some extent responsive to change in job strain levels.

Association between novel indices of malnutrition-inflammation complex syndrome and cardiovascular disease in hemodialysis patients

BACKGROUND

Inflammation and malnutrition are recognized as important risk factors for cardiovascular disease (CVD) in hemodialysis (HD) patients. Owing to substantial short-term variability of serum C-reactive protein (CRP), more reliable markers of malnutrition-inflammation complex syndrome should be sought with stronger associations with the risk of CVD in HD patients. We therefore explored the clinical relevance of a composite inflammatory index (prognostic inflammatory and nutritional index [PINI]) and of muscle protein mass indicators, derived from creatinine kinetics.

METHODS

This cross-sectional study included 177 HD patients (89 women and 88 men; median age, 67.73 years). CVD and risk factors were assessed using medical charts, clinical examination, and biochemical measurements performed at inclusion. Lean body mass (LBM) was derived from creatinine kinetic modeling, whereas PINI was calculated as the ratio (CRP xalpha1-acid-glycoprotein)/(albumin x transthyretin). Patients were divided according to the presence or absence of established CVD.

RESULTS

The traditional risk factors diabetes (odds ratio [OR], 5.83; p = 0.0045) and smoking (OR, 3.50; p < 0.02) were associated with an increase in prevalent CVD. Low transthyretin (OR, 3.79; p < 0.02) and high levels of CRP (OR, 2.70; p < 0.05), PINI (OR, 3.44; p < 0.02), observed LBM (OR, 3.01; p < 0.05), and the ratio of observed/expected LBM (OR, 4.24; p < 0.01) were associated with CVD after adjustment for age, sex, dialysis center, and dialysis vintage. After additional adjustment for diabetes and smoking, only PINI (OR, 2.85; p = 0.0446) and observed/expected LBM (OR, 2.96; p = 0.0361) were still significant.

CONCLUSION

PINI and LBM are associated with increased relative risk for having CVD and could be used routinely to examine the degree of severity of malnutrition inflammation complex syndrome.

Association between fasting glucose and C-reactive protein in a Japanese population: the Minoh study

To investigate the association between fasting glucose and C-reactive protein (CRP), we examined 1715 Japanese individuals (723 men and 992 women) aged 40-69 years who did not have medication for hypertension, diabetes, or dyslipidemia, a history of cardiovascular disease or CRP levels>10mg/l. There was a statistically significant unadjusted correlation between CRP and each component of the metabolic syndrome, including fasting glucose, fasting insulin, body mass index, systolic blood pressure, diastolic blood pressure, high-density lipoprotein cholesterol (negative), and triglycerides in both men and women. With adjustment for age, cigarette smoking, alcohol intake, and other components of the metabolic syndrome, the CRP increments (as back-transformed) compared with the lowest tertile of normal fasting glucose were 0.99, 1.05, 1.21, and 1.34mg/l (P for trend=0.008) with the second lowest and highest tertiles of normal fasting glucose, impaired fasting glucose, and type-2 diabetes, respectively in men. The respective adjusted CRP increments were 1.12, 1.23, 1.33, and 1.93mg/l (P for trend<0.001) in women. In the stratified analyses of CRP levels by sex, obesity status, and fasting glucose category or the number of components of the metabolic syndrome, an increase in CRP levels was greater in women than men with obesity and higher fasting glucose category (gender interaction: P<0.001) or an increased number of components of the metabolic syndrome (gender interaction: P=0.003). These results indicate that CRP levels increase continuously across the spectrum of fasting glucose in both sexes. This association is more pronounced in women.

Evaluation of C-Reactive Protein Measurement for Assessing the Risk and Prognosis in Ischemic Stroke

Background and Purpose— Several studies have shown, in different populations, that modest elevation of plasma C-reactive protein (CRP) in the range seen in apparently healthy individuals is a strong predictor of future vascular events. Elevated plasma CRP concentrations are also associated with an increased risk of cerebrovascular events and an increased risk of fatal and nonfatal cardiovascular events in ischemic stroke patients. These epidemiological and clinical observations suggest that determination of plasma CRP concentrations could be used as an adjunct for risk assessment in primary and secondary prevention of cerebrovascular disease and be of prognostic value. The aim of this review is to summarize the evidence for CRP as an independent predictor of cerebrovascular events in at-risk individuals and ischemic stroke patients and to consider its usefulness in evaluating prognosis after stroke.

Summary of Review— CRP fulfils most of the requirements of a new risk and prognostic predictor, but several issues await further confirmation and clarification before this marker can be included in the routine evaluation of stroke patients and subjects at risk for cerebrovascular disease. Potentially important associations have been established between elevated plasma CRP concentrations and increased efficacy of established therapies, particularly lipid-lowering therapy with statins.

Conclusion— At present, there is not sufficient evidence to recommend measurement of CRP in the routine evaluation of cerebrovascular disease risk in primary prevention, because there is insufficient evidence as to whether early detection, or intervention based on detection, improves health outcomes, although shared risk of cardiovascular disease indicates this may be of value. In secondary prevention of stroke, elevated CRP adds to existing prognostic markers, but it remains to be established whether specific therapeutic options can be derived from this.

C-Reactive Protein Concentration is More Strongly Related to Metabolic Syndrome in Women Than in Men-The Minoh Study-

BACKGROUND

The gender differences in the association between C-reactive protein (CRP) and features of the metabolic syndrome (MS) need to be elucidated among Japanese.

METHODS AND RESULTS

The study population included 715 men and 988 women aged 40-69 years who were not taking anti-hypertensive, lipid-lowering, hypoglycemic, anti-thrombotic, or non-steroidal anti-inflammation medications, and did not have a past history of cardiovascular disease or CRP concentration >10 mg/L. Except for high-density lipoprotein cholesterol, the unadjusted correlation between CRP and each MS component, including body mass index (BMI), systolic and diastolic blood pressures, triglycerides, fasting glucose, fasting insulin, and uric acid, was greater in women than in men. With adjustment for age, smoking status, and drinking status, the differences in CRP concentrations between those with the MS components of BMI, triglycerides, and uric acid and those without were greater in women than in men. Results of stratified analyses by the number of components of the MS of 0, 1, 2, 3, and > or = 4 revealed that an increase in CRP concentrations was greater in women than men with an increased number of components of the MS (gender interaction, p = 0.005). This tendency was observed in non-smokers, but not in current smokers (gender interaction, p = 0.013 and = 0.513, respectively).

CONCLUSIONS

CRP concentrations are closely related to the MS-like state in both sexes, but an increase in CRP concentration associated with risk factor-clustering is more pronounced in women, particularly non-smokers.

Non-invasive measurement of brachial-ankle pulse wave velocity is associated with serum C-reactive protein but not with alpha-tocopherol in Japanese middle-aged male workers

Pulse wave velocity (PWV) is an indicator of arterial stiffness, especially in the aorta, and a marker for vascular damage. We examined the association of brachial-ankle PWV (baPWV) with serum alpha-tocopherol and C-reactive protein (CRP) levels in addition to the traditional risk factors. Study subjects were 178 Japanese male workers aged 50-59 without past histories of cardiovascular diseases. The relation of baPWV with serum alpha-tocopherol and CRP levels was cross-sectionally analyzed after adjusting for other cardiovascular risk factors. The arithmetic mean of serum alpha-tocopherol was 38.9 micromol/l, and the geometric mean of serum CRP was 0.47 mg/l. Multiple linear regression analysis indicated that serum CRP levels were associated with an elevation of baPWV, in addition to age, systolic blood pressure and heart rate. However, serum alpha-tocopherol, serum lipids (triglyceride, low and high density lipoprotein cholesterol), fasting plasma glucose, body mass index, smoking and alcohol drinking did not significantly correlate to baPWV. Multivariate-adjusted means of baPWV according to serum CRP quartile were 1,431, 1,436, 1,507 and 1,508 cm/s (p = 0.033). The serum CRP level might be an important marker for arterial stiffness in Japanese middle-aged males. However, no relation was observed between alpha-tocopherol and baPWV.

C-reactive protein genotypes affect baseline, but not exercise training-induced changes, in C-reactive protein levels

OBJECTIVE

The goal of this study is to determine whether C-reactive protein (CRP) gene variants affect baseline and training-induced changes in plasma CRP levels.

METHODS AND RESULTS

Sixty-three sedentary men and women aged 50 to 75 years old underwent baseline testing (Vomax, body composition, CRP levels). They repeated these tests after 24 weeks of exercise training while on a low-fat diet. The CRP +219G/A variant significantly associated with CRP levels before and after training after accounting for the effects of demographic and biological variables. CRP -732A/G genotype was significantly related on a univariate basis to CRP levels after training. The CRP +29T/A variant did not affect CRP levels before or after training. In regression analyses, the +219 and -732 variants each had significant effects on CRP levels before and after training. Subjects homozygous for the common A/G -732/+219 haplotype exhibited the highest CRP levels, and having the rare allele at either site was associated with significantly lower CRP levels. CRP levels decreased significantly with training (-0.38+/-0.18 mg/L; P=0.03). However, none of the CRP variants was associated with the training-induced CRP changes.

CONCLUSIONS

CRP +219G/A and -732A/G genotypes and haplotypes and exercise training appear to modulate CRP levels. However, training-induced CRP reductions appear to be independent of genotype at these loci.

No association between pre-diagnostic plasma C-reactive protein concentration and subsequent prostate cancer

BACKGROUND

We evaluated the association of pre-diagnostic plasma concentration of C-reactive protein, a sensitive, but non-specific indicator of inflammation, with subsequent risk of prostate cancer.

METHODS

Included were 264 histologically confirmed prostate cancer cases and 264 age-matched controls who were participants in the CLUE II cohort of Washington County, MD. C-reactive protein was measured using a high-sensitivity immunoturbidimetric assay. Odds ratios (ORs) and 95% confidence intervals (CI) were estimated from conditional logistic regression models by fourth of the C-reactive protein distribution with cutpoints based on the controls. The median concentrations from the lowest to highest fourth were 0.41, 1.03, 1.90, and 4.53 mg/L.

RESULTS

Geometric mean plasma concentrations did not differ between the cases (1.24 +/- 2.94 mg/L) and controls (1.41 +/- 2.97 mg/L; P = 0.16). Compared to the bottom fourth, the ORs (95% CI) of prostate cancer were 1.29 (0.80-2.08), 0.98 (0.61-1.58), and 0.95 (0.57-1.58) for the second, third, and highest fourths (P trend = 0.66). These findings were unchanged after adjusting for body mass index (BMI) and cigarette smoking status or after excluding men with markedly elevated C-reactive protein, cases diagnosed during the first 2 years of follow-up, or controls who never had a PSA test. These findings did not differ by stage or grade of prostate cancer.

CONCLUSIONS

Pre-diagnostic plasma concentration of C-reactive protein was not associated with subsequent risk of prostate cancer.

C-reactive protein and other circulating markers of inflammation in the prediction of coronary heart disease

BACKGROUND

C-reactive protein is an inflammatory marker believed to be of value in the prediction of coronary events. We report data from a large study of C-reactive protein and other circulating inflammatory markers, as well as updated meta-analyses, to evaluate their relevance to the prediction of coronary heart disease.

METHODS

Measurements were made in samples obtained at base line from up to 2459 patients who had a nonfatal myocardial infarction or died of coronary heart disease during the study and from up to 3969 controls without a coronary heart disease event in the Reykjavik prospective study of 18,569 participants. Measurements were made in paired samples obtained an average of 12 years apart from 379 of these participants in order to quantify within-person fluctuations in inflammatory marker levels.

RESULTS

The long-term stability of C-reactive protein values (within-person correlation coefficient, 0.59; 95 percent confidence interval, 0.52 to 0.66) was similar to that of both blood pressure and total serum cholesterol. After adjustment for base-line values for established risk factors, the odds ratio for coronary heart disease was 1.45 (95 percent confidence interval, 1.25 to 1.68) in a comparison of participants in the top third of the group with respect to base-line C-reactive protein values with those in the bottom third, and similar overall findings were observed in an updated meta-analysis involving a total of 7068 patients with coronary heart disease. By comparison, the odds ratios in the Reykjavik Study for coronary heart disease were somewhat weaker for the erythrocyte sedimentation rate (1.30; 95 percent confidence interval, 1.13 to 1.51) and the von Willebrand factor concentration (1.11; 95 percent confidence interval, 0.97 to 1.27) but generally stronger for established risk factors, such as an increased total cholesterol concentration (2.35; 95 percent confidence interval, 2.03 to 2.74) and cigarette smoking (1.87; 95 percent confidence interval, 1.62 to 2.16).

CONCLUSIONS

C-reactive protein is a relatively moderate predictor of coronary heart disease. Recommendations regarding its use in predicting the likelihood of coronary heart disease may need to be reviewed.

Genetic effects on baseline values of C-reactive protein and serum amyloid a protein: a comparison of monozygotic and dizygotic twins

BACKGROUND

C-Reactive protein (CRP) and serum amyloid A protein (SAA) are exquisitely sensitive acute-phase reactants, but their baseline values are surprisingly constant in individuals in the general population. These values, especially of CRP, are associated with future atherothrombotic events, and the determinants of baseline CRP and SAA concentration are therefore of considerable interest.

METHODS

CRP and SAA concentrations were measured by well-validated automated microparticle capture enzyme immunoassays, standardized on the respective WHO International Reference Standards, in serum from 146 monozygotic and 164 dizygotic healthy female UK twin pairs from the general population, with mean (range) ages of 58.0 (40-69.6) and 55.7 (40-70.3) years, respectively, who were also very closely matched for height, weight, body mass index, blood pressure, and lifestyle variables. Statistical modeling based on variance components analysis was used to estimate the genetic contribution to the observed values.

RESULTS

As reported previously, CRP values were associated with body mass index, smoking, and hormone replacement therapy. After exclusion of the few samples with CRP concentrations >10 mg/L, which indicate an ongoing acute-phase response rather than baseline values, and inclusion of adjustments for all known confounding variables, there was significantly higher correlation of CRP and SAA results among monozygotic than among dizygotic twins. The estimated hereditability (95% confidence interval) of baseline values was 52% (40-62%) for CRP and 59% (49-67%) for SAA.

CONCLUSION

There is a substantial genetic contribution to baseline serum concentrations of CRP and SAA.

Association of body mass index, body fat, and weight gain with inflammation markers among rural residents in Japan

Because obesity is thought to play a key role in atherosclerosis through the low-grade chronic inflammation, the present study was designed to investigate associations of body mass index (BMI), body fat, and weight gain with optimized inflammation markers in 1,053 residents who were 40 years of age and older from a rural community (total population = 3,940 in 2000) in Japan. People reporting having a cold and those who did not undergo blood examinations were excluded. C-reactive protein (CRP), fibrinogen, serum albumin, and white blood cell (WBC) count were used as the markers for inflammation, body fat was calculated by a conventional method, and weight change since the age of 20 was assessed. The BMI and body fat significantly increased with CRP quartile, and its correlation coefficients to BMI or body fat were relatively high. Similar associations were found for fibrinogen, serum albumin and WBC. Multivariate-adjusted analysis found a high concentration of CRP was significantly associated with obesity, but attenuated the association in other markers. In an analysis restricted to people aged 40-69 years, body fat levels were more strongly associated with CRP and fibrinogen than with BMI only. Furthermore, only CRP concentrations were significantly elevated according to weight gain. Strong associations of CRP concentration with BMI, body fat, and weight gain were found among elderly Japanese, but not with fibrinogen, serum albumin or WBC.

Higher C-reactive protein concentration and white blood cell count in subjects with more coronary risk factors and/or lower physical fitness among apparently healthy Japanese

Of 2,722 people (1.876 men, mean age: 51.3+/-10.3 years; 846 women, mean age: 51.4+/-11.1) who underwent the fitness check program at Aichi Prefectural Center for Health Care, the concentration of C-reactive protein (CRP) and the white blood cell count (WBC) were investigated in relation to the number of coronary risk factors, maximum oxygen uptake (VO2max) quartiles and physical fitness score. CRP was measured by conventional latex immunoturbidimetric assay. Both CRP and WBC were higher in those who had more risk factors. In men the lowest mean CRP was 0.07 mg/dl in those with only one risk factor (RF1) and the highest was 0.29 mg/dl in RF6 (p<0.0001). The lowest mean WBC was 4,868/mm3 in RF1 and the highest was 7,096/mm3 in RF6 (p<0.0001). In women the lowest mean CRP was 0.073 mg/dl in those with no risk factors (RF0) and the highest was 0.22mg/dl in RF5 (p=0.0379). The lowest mean WBC was 5,065/mm3 in RF1, and the highest was 6,792/mm3 in RF4 (p=0.0001). A similar relationship was noticed when the groups were analyzed by VO2max quartile or fitness score. CRP and WBC both showed a stepwise increase or decrease in men, but was generally in order in women in accordance with the number of risk factors, VO2max level or fitness score. In apparently healthy Japanese subjects, elevated inflammatory indices (ie, higher CRP and WBC) were associated with more coronary risk factors and poorer physical fitness. Therefore, high-risk coronary subjects might be screened by conventional measurement of CRP.

Association of seropositivity for antibody to Chlamydia-specific lipopolysaccharide and coronary artery disease in Japanese men

Recent studies suggest an association between Chlamydia pneumoniae infection and coronary artery disease (CAD). To examine this relationship in Japanese men, serum IgA and IgG antibodies to Chlamydia-specific lipopolysaccharide were measured by enzyme-linked immunosorbent assay in 507 patients with CAD and 200 age-matched controls. CAD patients were divided into (1) 269 patients with myocardial infarction (MI) and (2) 238 patients with chronic coronary heart disease (CCHD). Compared with the control group, the CAD group did not differ in the prevalences of both antibodies (IgA: 23.7 vs 18.0%, p=0.10; IgG: 52.7 vs 51.0%, p=0.6). The index of IgG antibody was not significantly different between CAD and control groups (median 1.19 vs 1.18, p=0.3), whereas the index of IgA antibody was significantly higher in CAD than control group (median 0.60 vs 0.46, p<0.0001). Compared with the control group, the MI group had a significantly higher prevalence of IgA antibody (28.6 vs 18.0%, p=0.007); however, there was no difference in the prevalence of IgG antibody (58.0 vs 51.0%, p=0.13). The CCHD group did not differ in the prevalences of both antibodies (IgA: 18.1 vs 18.0%, p=0.9; IgG: 45.6 vs 51.0%, p=0.2). After the adjustment for coronary risk factors, odds ratios (ORs) of seropositive antibodies for CAD were 1.59 [95% confidence interval (CI): 0.88-2.87, p=0.12] for IgA seropositivity and 0.92 (95%CI: 0.58-1.47, p=0.7) for IgG seropositivity in all cases. In the MI and control groups, ORs of seropositive antibodies for MI were 2.67 (95%CI: 1.32-5.38, p=0.007) for IgA seropositivity, and 1.36 (95%CI: 0.79-2.36, p=0.2) for IgG seropositivity. This study discovered that IgA antibody to Chlamydia was significantly associated with CAD, especially with MI, in Japanese Men and the findings suggest that chronic infection of Chlamydia may be linked to the pathogenesis of MI.