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PubMed1985

Longitudinal correlation analysis of standing height and intelligence.

Intercorrelations of 10 successive years of measurement of height and intelligence are presented for separate samples of girls and boys. These correlations are based on data originally gathered and published by Dearborn, Rothney, and Shuttleworth as the Harvard Growth Study. Sample size varies from correlation to correlation, but most of those for girls are based on samples of 500-700 and those for boys on samples of 400-500. The intercorrelations of each of the 2 variables over 10 occasions do not differ appreciably by sex, but there are significant differences between the sexes in the cross-correlations. For the sample of girls there is clear evidence that individual differences in height at 8 and 9 anticipate later individual differences in intelligence. Correlations of early height with intelligence at 11 and 12 are especially high (.40). There is little evidence for similar anticipation of intelligence by height for boys. Correlates for both height and intelligence are found in socioeconomic status, ethnicity, and age of first menstruation for girls. Only the last of these contributes to the explanation of the changes in the cross-correlations with age. Analyses of sitting-height correlations with intelligence indicate that length of the long bones of the legs is also related to the observed pattern of correlations.

Adolescent↗

PubMed1981

Epidemiological correlations between diet and cancer frequency.

The literature concerning international correlations between dietary items and cancer frequency is reviewed. An updated correlation of the most recent data on cancer mortality and food consumption is made. Strong and consistent correlations are reported between death rates of cancers of the colon and breast and the per capita consumption of total fat and of nutrients derived from animal sources, especially beef, pork, eggs, and milk. Similar but less consistent correlations have been reported with cancers of the prostate, ovary, and endometrium. In addition, correlations between precursor lesions of coronary heart disease and colon cancer in New Orleans autopsy populations are reported. Some studies suggest that milk intake correlates better with atherosclerotic disease while beef intake correlates better with colon cancer. Negative correlations of colon cancer rates and vegetable consumption are reported. Colon cancer rates also show negative correlations with stool weight, irrespective of the type of vegetable responsible for the increased bulk. Epidemiological data are consistent with the hypothesis that excessive beef and low vegetable consumption are causally related to colon cancer. These food items probably do not have a direct carcinogenic role but rather provide a microenvironment favorable to the actions of carcinogens.

Breast Neoplasms↗

PubMed1984

Quantitative genetics and the evolution of ontogeny. II. Genetic and environmental correlations among age-specific characters in randombred house mice.

In this study, phenotypic, genetic, maternal and residual environmental correlations among all pairs of six ages (17, 24, 31, 38, 45 and 52 days) were calculated for each of five morphometric characters (body weight, head length, trunk length, trunk circumference, and tail length) in ICR randombred house mice. The maternal correlations between ages averaged nearly unity for all characters, and the overall level (and integration, I) of the genetic correlations (mean level = 0.82, mean I = 0.85) was greater than that for the residual environmental correlations (mean level = 0.26, mean I = 0.32). The patterns of the phenotypic and genetic correlations were similar, with the highest correlations being between contiguous ages and a relatively smooth decrease in correlations for increasingly distant ages. Nearly all of the genetic covariation among ages was explained by the first (average = 86%) and second (average = 14%) components derived from principal components analysis of the genetic correlations. Genes with basically equal pleiotropic effects presumably generated the first component, genes with different effects among ages the second component. From the patterns of genetic correlations, it is predicted that direct selection on any given age would result in a moderate, positive response at most other ages, with more change in the height relative to the shape of the growth curve for each characteristic.

Aging↗

PubMed1984

Correlations between cancer incidence rates from the Canadian National Cancer Incidence Reporting System, 1969-78.

Incidence rates for 19 cancers in females and 16 cancers in males have been computed from data reported by 8 Canadian provinces to the National Cancer Incidence Reporting System between 1969 and 1978. The rates, very similar in absolute and relative magnitude to those reported by the U.S. Third National Cancer Survey, have been used to examine patterns of correlation between various cancers within the 8 provinces. There is strong evidence of positive associations between a number of cancers, including a number of associations that have been reported in other similar correlational studies. Correlations that may be of particular interest in suggesting etiologic factors in common include clusters of smoking-related cancers (buccal cavity with pharynx, larynx, lung, and bladder), female sexual cancers (breast, corpus uteri, and ovary), and a group of cancers that have shown correlation in other studies (i.e., cancers of the pancreas and kidney, leukemias, lymphomas, and cancer of the prostate gland). Organs in the gastrointestinal tract (esophagus, stomach, colon, and rectum) anatomically close to each other show a high positive correlation in both females and males, but the further apart the organs are the lower is the correlation; these observations are consistent with other evidence of varying dietary etiologies. Two individual correlations of particular interest are those between female brain tumors and female bladder cancer (two cancers for which little is known of the etiology for a large percentage of them) and those between female breast cancer and female lung cancer. This study, the largest correlational study of incidence data reported to date, demonstrates the utility of such simple correlational analyses.

Canada↗

PubMedDate not supplied

Inter-individual variability in blood/air partitioning of volatile organic compounds and correlation with blood chemistry.

In vitro blood/air partition coefficients (KB/A) for acetone, 1,1,1-trichloroethane, toluene, and styrene were measured in blood samples from 73 human subjects and correlated with blood chemistry parameters (hematocrit, total cholesterol, serum triglycerides, serum albumin, total plasma proteins, Na+, K+, Cl-, and HCO3-). Statistically significant inter-individual variation existed in KB/A between some subjects. Substitution of group or generic in vitro KB/A values for values determined in some individuals could introduce errors of up to 50%. However, most subjects could be well represented by group averages (mean +/- SD; acetone, 301 +/- 22; 1,1,1-trichloroethane, 6.0 +/- 0.8; toluene, 19 +/- 3; styrene, 62 +/- 10). The KB/A values for acetone, 1,1,1-trichloroethane and toluene were normally distributed. The data for styrene appeared to deviate from a normal distribution and may have been bimodal. The KB/A values for the two structurally related compounds, toluene and styrene, were strongly correlated within individuals, while the KB/A values for compounds with less structural similarity, such as acetone and styrene, were poorly correlated. At most, 15% of the variation in KB/A among individuals could be explained by variation in the measured blood chemistry parameters. When the entire sample group was considered, blood chemistry parameters were not significantly correlated with KB/A for any compound. The KB/A of 1,1,1-trichloroethane was significantly correlated with the concentration of cholesterol and triglycerides in females. Sex was a significant grouping variable for the correlation of albumin concentration with the KB/A of styrene. Age was not a significant correlation variable. Blood chemistry parameters which previously have been correlated with KB/A in small sample groups do not appear to be significantly correlated in our larger sample group.

Acetone↗

PubMedDate not supplied

Cancer mortality and poverty in Argentina: a geographical correlation study.

Age-standardized mortality rates of cancer were calculated for the Argentine provinces using deaths from 7 years of registration (1980-1986). Correlations between the geographical distributions of the rates for the main causes of death by cancer were analyzed. The correlations were adjusted for socioeconomic status using an indicator of low socioeconomic level (NBI) as a third variable in a multivariate analysis or stratifying by NBI. Correlations between the distribution of the age-standardized mortality rates in males and females for the same tumor site also were analyzed. Positive intersex correlations were observed for mortality rates of cancers of the colon, liver, pancreas, esophagus, stomach, gallbladder, and bladder. Negative correlations with NBI were observed for cancers of the breast and ovary in females, colon and pancreas in both sexes, and bladder in males. Positive correlations with NBI were observed for cancer of the cervix and for all uterine cancers. After adjusting by NBI, only the correlations between the distributions of cancer of the lung and cancers of the bladder, larynx, and pancreas in males remained statistically significant. The stratified analysis showed changes in the values of many of the correlation indexes by level of NBI. It is concluded that the socioeconomic level, measured by the NBI, is a strong confounder and an effective modifier of many correlations presented.

Adolescent↗

PubMed1994

Genetic and environmental correlations among skinfold measures.

A bivariate genetic analysis, utilizing variance decomposition techniques based on maximum likelihood methods, was undertaken to examine the genetic and environmental correlations among eight skinfolds in a large pedigreed sample of Mexican Americans from San Antonio, Texas. The resulting correlation coefficients reveal significant values for both the genetic and environmental components among the traits examined. The genetic correlation coefficients showed the highest values between skinfolds from the same region (i.e., triceps, biceps, and forearm), while the environmental correlation remained fairly constant between all traits. These findings are further supported by a principal component analysis of the phenotypic, genetic, and environmental correlation matrices. This represents the first study to partition the phenotypic correlation between these traits into their genetic and environmental components. An examination of the graphical representations of the eigenvectors of these correlation matrices reveals that the patterns of central versus peripheral fat distribution seen in the phenotypic correlation matrix are largely a function of the genetic correlation structure. All these findings are interpreted as evidence of a global pleiotropic effect in the genetic expression of these traits, with what might be secondary regional pleiotropic effects among specific subsets of the skinfolds. In addition it appears that these pleiotropic effects exist against a background of a relatively constant shared environmental effect. It is concluded that these traits are not independent with respect to either shared genetic or environmental influences.

Adolescent↗

PubMed1993

[Study of Navarra (PECNA). Correlation of arterial blood pressure, in a child-young population, with anthropometric and biochemical parameters].

As part of an epidemiological study on cardiovascular risk factors among children and adolescent in Navarra, arterial blood pressure (BP) readings were taken in 5,829 children. These children, both males and females, between the ages of 4 and 17 years, were selected at random from the public and private school population in our community. The correlation between systolic blood pressure and diastolic blood pressure with anthropometric and biochemical parameters was analyzed. The correlation coefficient for systolic BP readings were always higher than those for diastolic BP. The highest correlations for both BP scores were found with weight, followed by height. Correlation with total weight parameters is superior to that found with body fat parameters. There were no significant correlations between BP and the lipid parameters. When analyzing multiple regression equations, we find that with only the child's weight and age, both systolic and diastolic BP can be predicted with correlation coefficients of 0.597 and 0.492, respectively. When doing a partial correlation analysis, the correlation between systolic BP and age, at a fixed height value, disappears; while the correlation of systolic BP with height remains when using a set age. This suggest that the best definition for hypertension is based on BP-height percentile, rather than BP-age.

Adolescent↗

PubMed1996

Significant correlation of the American Urological Association symptom score and a novel urodynamic parameter: detrusor contraction duration.

PURPOSE: Various investigators have reported the lack of specificity of the American Urological Association (AUA) symptom score and its poor correlation with urodynamic parameters. A retrospective study was performed to ascertain the correlation of the AUA symptom score with various urodynamic parameters, including detrusor contraction duration. MATERIALS AND METHODS: The urodynamic records of 120 consecutive patients with moderate (scores 8 to 19) or severe (scores greater than 19) symptoms were retrospectively analyzed to ascertain if the AUA symptom score correlated with the urodynamic parameters of maximum detrusor pressure, detrusor pressure at maximum flow, compliance, involuntary detrusor contractions and, a novel parameter, detrusor contraction duration. RESULTS: There were 63 men (mean age 59.7 years) and 57 women (mean age 58.8 years). Mean AUA symptom score plus or minus standard deviation was 17.8 +/- 3.7 and 15.4 +/- 2.9, respectively. There was no correlation between any urodynamic parameter and symptoms in women. In men increasing symptoms were associated with worsening urodynamic parameters. The 2 parameters that had the greatest correlation with symptom severity were incidence of involuntary detrusor contractions (r = 0.56, p < 0.006) and detrusor contraction duration (r = 0.61, p < 0.003). Furthermore, increasing incidence of involuntary detrusor contractions was associated with increasing irritative symptoms, while increasing detrusor contraction duration was correlated with increasing obstructive symptoms. Detrusor contraction duration was correlated with symptom severity and urodynamic outlet obstruction in men. CONCLUSIONS: These data demonstrated that the AUA symptom score correlates with certain urodynamic parameters. Furthermore, this correlation occurs in men in contrast to women despite similar AUA symptom scores. In addition, increasing detrusor contraction duration is associated with worsening symptoms and may herald worsening obstruction. Further prospective studies are underway to determine the prognostic value of these urodynamic parameters in altering ultimate outcomes of treatment.

Female↗

PubMed2000

Dispersal, Environmental Correlation, and Spatial Synchrony in Population Dynamics.

Many species exhibit widespread spatial synchrony in population fluctuations. This pattern is of great ecological interest and can be a source of concern when the species is rare or endangered. Both dispersal and spatial correlations in the environment have been implicated as possible causes of this pattern, but these two factors have rarely been studied in combination. We develop a spatially structured population model, simple enough to obtain analytic solutions for the population correlation, that incorporates both dispersal and environmental correlation. We ask whether these two synchronizing factors contribute additively to the total spatial population covariance. We find that there is always an interaction between these two factors and that this interaction is small only when one or both of the environmental correlation and the dispersal rate are small. The interaction is opposite in sign to the environmental correlation; so, in the normal case of positive environmental correlation across sites, the population synchrony will be lower than predicted by simply adding the effects of dispersal and environmental correlation. We also find that population synchrony declines as the strength of population regulation increases. These results indicate that dispersal and environmental correlation need to be considered in combination as explanations for observed patterns of population synchrony.

Moran effect↗

PubMed2005

Correlation between serum levels of insulin-like growth factor 1, dehydroepiandrosterone sulfate, and dihydrotestosterone and acne lesion counts in adult women.

OBJECTIVES: To determine if insulin-like growth factor 1 (IGF-1) and androgen levels (1) correlate with the presence and severity of acne in adult men and women, and (2) correlate directly with each other and interact in affecting acne. DESIGN: Case-control study and single-center examination of hormone levels in a cohort of volunteers. SETTING: Academic referral center. PATIENTS: Thirty-four subjects (8 women and 8 men with clinical acne, 10 women and 8 men without clinical acne). Clinical acne is defined by a history of persistent acne (acne present on most days for several years), recent acne treatment, and the presence of 10 or more inflammatory acne lesions and 15 or more comedones. INTERVENTIONS: Single visit for serum sampling. MAIN OUTCOME MEASURES: Serum levels of IGF-1 and androgens were determined, adjusted for age, and compared based on the presence or absence of clinical acne using an analysis of covariance. Correlations between hormone levels and acne lesion counts were calculated within each subgroup. Correlations were also calculated between serum levels of IGF-1 and androgens. Further statistical testing was conducted to determine whether IGF-1 or androgens had a greater effect on acne lesion counts. RESULTS: Dehydroepiandrosterone (DHEAS), dihydrotestosterone (DHT), and IGF-1 correlated positively with acne lesion counts in women. Androstenedione and DHEAS correlated with acne lesion counts in men. Although the age-adjusted mean serum levels of IGF-1 were higher in women with clinical acne than in women without clinical acne, this difference did not achieve statistical significance. No difference in IGF-1 level was noted in men based on the presence of clinical acne. In women with clinical acne, IGF-1 correlated with DHT. In men with clinical acne, IGF-1 correlated with DHEAS and androstenedione. In men and women with clinical acne, the effects of androgens on increased acne lesion counts were dependent on the influence of IGF-1. CONCLUSIONS: Increased IGF-1 levels in addition to androgens may influence acne in adult men and women. While IGF-1 appears to have a stronger effect on acne in women, androgens may play a greater role in acne for men. However, in both men and women these hormones are interrelated, possibly owing to reciprocal effects on hormone production.

Acne Vulgaris↗

PubMed2006

Hospital quality for acute myocardial infarction: correlation among process measures and relationship with short-term mortality.

CONTEXT: The Centers for Medicare & Medicaid Services (CMS) and the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) measure and report quality process measures for acute myocardial infarction (AMI), but little is known about how these measures are correlated with each other and the degree to which inferences about a hospital's outcomes can be made from its performance on publicly reported processes. OBJECTIVE: To determine correlations among AMI core process measures and the degree to which they explain the variation in hospital-specific, risk-standardized, 30-day mortality rates. DESIGN, SETTING, AND PARTICIPANTS: We assessed hospital performance in the CMS/JCAHO AMI core process measures using 2002-2003 data from 962 hospitals participating in the National Registry of Myocardial Infarction (NRMI) and correlated these measures with each other and with hospital-level, risk-standardized, 30-day mortality rates derived from Medicare claims data. MAIN OUTCOME MEASURES: Hospital performance on AMI core measures; hospital-specific, risk-standardized, 30-day mortality rates for AMI patients aged 66 years or older. RESULTS: We found moderately strong correlations (correlation coefficients > or =0.40; P values <.001) for all pairwise comparisons between beta-blocker use at admission and discharge, aspirin use at admission and discharge, and angiotensin-converting enzyme inhibitor use, and weaker, but statistically significant, correlations between these medication measures and smoking cessation counseling and time to reperfusion therapy measures (correlation coefficients <0.40; P values <.001). Some process measures were significantly correlated with risk-standardized, 30-day mortality rates (P values <.001) but together explained only 6.0% of hospital-level variation in risk-standardized, 30-day mortality rates for patients with AMI. CONCLUSIONS: The publicly reported AMI process measures capture a small proportion of the variation in hospitals' risk-standardized short-term mortality rates. Multiple measures that reflect a variety of processes and also outcomes, such as risk-standardized mortality rates, are needed to more fully characterize hospital performance.

Aged↗

PubMed1998

Expression of growth factors, growth-inhibiting factors, and their receptors in invasive breast cancer. II: Correlations with proliferation and angiogenesis.

Growth factors may play an important role in tumour growth and angiogenesis by their influence on tumour cell proliferation or their effect on neovascularization. The aim of the present study was to determine which of the growth factors, growth-inhibiting factors, and their receptors investigated in a previous study are correlated with proliferation and angiogenesis in invasive breast cancer, with emphasis on the impact of possible autocrine and paracrine loops. Five growth factors and their receptors: platelet-derived growth factor A chain (PDGF-AA) and PDGF alpha receptor (PDGF alpha R), PDGF-BB and PDGF beta receptor (PDGF beta R), transforming growth factor alpha (TGF alpha) and its receptor epidermal growth factor receptor (EGFR), and vascular endothelial growth factor (VEGF) and its receptors (Flt-1 and Flk-1/KDR; two growth-inhibiting factors: transforming growth factor beta-1 (TGF beta 1) and TGF beta 2 and their receptor couple TGF beta R-I and TGF beta R-II; and basic fibroblast growth factor (bFGF) were stained in 45 cases of invasive breast cancer by standard immunohistochemistry on frozen sections. Staining in tumour cells, stromal cells, and endothelial cells was scored as negative or positive. Proliferation was determined by assessment of the mitotic activity index (MAI) and the degree of angiogenesis was measure by counting the number of microvessels (microvessel density: MVD) in the most vascularized area of the tumour. bFGF and EGFR showed positive correlations with the MAI, while TGF beta 2 showed a negative correlation. Expression of bFGF, TGF alpha, TGF beta 2, and EGFR correlated positively with the MVD. Co-expression of the TGF alpha/EGFR growth factor/receptor combination showed a stronger correlation with the MAI and the MVD than EGFR or TGF alpha alone, and the TGF beta 2/TGF beta R-I/TGE beta R-II combination showed a positive correlation with the MVD. In conclusion, the expression of several growth factors, growth factor receptors and growth-inhibiting factors showed correlations with the rate of proliferation and the degree of angiogenesis in invasive breast cancer. Some growth factor/receptor combinations showed stronger correlations with proliferation and angiogenesis than the growth factor or receptor alone, pointing to the importance of possible auto- and paracrine loops for stimulation of proliferation and angiogenesis by growth factors and their receptors.

Autocrine Communication↗

PubMed2000

Clock drawing test: correlation with linear measurements of CT studies in demented patients.

OBJECTIVES: To investigate a presumed correlation between clock drawing ratings and linear measurements of computerized tomography (CT) studies in demented patients. DESIGN: Blinded evaluations of clock drawing tests and CT studies of elderly dementia patients were conducted by a geriatric psychiatrist and a neuroradiologist. SUBJECTS: Fifty-one community-dwelling elderly subjects meeting the criteria for DSM-IV diagnosis of dementia (Alzheimer's type dementia: N=31; vascular dementia: N=15; "mixed" type dementia: N=5). MATERIALS: Mini-Mental State Examination (MMSE), Cambridge Cognitive Examination (CAMCOG), Clinical Dementia Rating (CDR). CAMCOG derived scored clock drawings were evaluated using adaptations of Shulman et al.'s and Freedman et al.'s methods. CT studies were evaluated using six different linear measurements of brain atrophy described in the literature. RESULTS: Of the CT linear measurements, only the Cerebro-Ventricular Index-2 (CVI-2; bicaudate index) significantly correlated with clock drawing ratings (CAMCOG's clock r=-0.407, p=0.003; Shulman's method r=0.357, p=0.01, Freedman's method r=-0.413, p=0.003) in the dementia group. There was no significant correlation between CVI-2 with demographic (age), cognitive (MMSE, CAMCOG) and clinical (duration of illness, CDR) ratings. Alzheimer's patients generally maintained a significant correlation between CVI-2 and clock drawings, but vascular dementia patients did not; CVI-2 also correlated significantly with the Praxis subtest of the CAMCOG in dementia and Alzheimer's patients but not in the vascular dementia group. Similarly, multiple stepwise regression analysis showed that only CVI-2 but not the other radiological measures studied, was selected as the significant variable to correlated with clock drawing test ratings in the dementia group and Alzheimer's patients. Partial correlation analysis controlling for demographic and clinical variables shows that controlled variables had no significant effect on the relationship between clock drawing ratings and CVI-2. CONCLUSION: A single and easy to perform measure of caudate atrophy correlates specifically and consistently with impairments revealed in the clock drawing test and with a Praxis subtest, suggesting possible caudate involvement with clock drawings in dementia in general and of the Alzheimer's type in particular.

Aged↗

PubMed1987

Familial correlations from genes and shared environment for urine, plasma, and intraerythrocytic sodium.

Spouse-spouse, sib-sib, and parent-offspring correlations were calculated for urinary, plasma, and intracellular sodium levels on over 1,900 persons aged 3-86 years in 98 Utah kindreds. For 36 hours prior to their clinic visit, 31% of the sample was salt-loaded with salt tablets, while the rest followed their normal diet. For those on their normal diet, urine creatine-, age-, and sex-adjusted urinary sodium excretion from a timed 12-hour overnight sample showed similar and significant correlations between spouses (r = .29), sibs less than 20 years old (r = .38), and parent-offspring pairs for offspring less than 20 years old (r = .29). This contrasted with the lower correlations between sibs 20 years of age and older (r = .10) and parent-offspring pairs for offspring 20 years of age and older (r = .13), presumed to live in different households. Adult plasma sodium sib-sib (r = .13) and parent-offspring (r = .15) correlations were similar to the urinary sodium correlations, while the spouse-spouse (r = .48), the sib-sib (r = .64), and the parent-offspring (r = .63) correlations for those presumed to live in the same household nearly doubled. Intracellular sodium correlations for the adult sibs (r = .32) and offspring (r = .36) were over twice as large as for urinary or plasma sodium, although the spouse-spouse correlation (r = .37) remained large also.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1981

Quantitative genetics of skeletal nonmetric traits in the rhesus macaques on Cayo Santiago. II. Phenotypic, genetic, and environmental correlations between traits.

The general lack of phenotypic correlation among skeletal nonmetric traits has been interpreted as indicating a lack of genetic correlation among these traits. Nonmetric traits scored on animals in the skeletal collection of rhesus macaques from Cayo Santiago are used to calculate phenotypic, genetic, and environmental correlations between traits. The results show that even when phenotypic correlations are low, there may be large, significant genetic correlations among these traits. The genetic correlation pattern suggests that genes which affect nonmetric trait variation act primarily at a local level in the cranium, even though there are genes with pleiotropic effects on skeletal nonmetric traits throughout the cranium. Environmental and phenotypic correlations do not show this neighborhood pattern of correlation.

Animals↗

PubMed2006

Correlation between juvenile idiopathic arthritis activity and damage measures in early, advanced, and longstanding disease.

OBJECTIVE: To compare the correlation between juvenile idiopathic arthritis (JIA) measures of disease activity and damage in patients with early and late disease. METHODS: Three cohorts of patients with JIA disease duration < or =1 year (early disease, n = 70), 5-9.9 years (advanced disease, n = 114), and > or =10 years (longstanding disease, n = 39) were studied. Measures included physician's global assessment of overall disease activity (MD global), parent's global assessment of the child's well-being (parent global) and pain (parent pain), joint counts, Childhood Health Assessment Questionnaire (CHAQ), erythrocyte sedimentation rate, C-reactive protein level, and Poznanski score of radiographic damage. RESULTS: In all cohorts, the MD global assessment was generally well correlated with the other variables, except the Poznanski score. The parent global assessment was correlated strongly with the parent pain assessment and moderately with the CHAQ irrespective of disease duration. Correlations between the CHAQ and the joint counts were low in early disease, moderate in advanced disease, and high to moderate in longstanding disease. Correlation between the CHAQ and the Poznanski score was low in early and advanced disease and moderate in longstanding disease. The Poznanski score was highly correlated with the number of joints with restricted motion in longstanding disease. CONCLUSION: We found important differences in the level of correlation between JIA measures of activity and damage in patients with different lengths of disease duration. These findings have important implications for clinical trials because they indicate that the responsiveness of some variables and their correlation with other variables change as disease duration changes.

Adolescent↗

PubMed1994

Correlations among indices of electric and magnetic field exposure in electric utility workers.

Power-frequency electric and magnetic fields are known to exhibit marked temporal variation, yet in the absence of clear biological indications, the most appropriate summary indices for use in epidemiologic studies are unknown. In order to assess the statistical patterns among candidate indices, data on 4383 worker-days for magnetic fields and 2082 worker-days for electric fields collected for the Electric and Magnetic Field Project for Electric Utilities using the EMDEX meter [Bracken (1990): Palo Alto, CA: Electric Power Research Institute] were analyzed. We examined correlations at the individual and job title group levels among indices of exposure to both electric and magnetic fields, including the arithmetic mean, geometric mean, median, 20th and 90th percentiles, time above lower cutoffs of 20 V/m and 0.2 microT, and time above higher cutoffs of 100 V/m and 2.0 microT. For both electric and magnetic fields, the arithmetic mean was highly correlated with the 90th percentile; moderately correlated with the geometric mean, median, and lower and higher cutoff scores; and weakly correlated with the 20th percentile. Electric and magnetic field indices were generally weakly correlated with one another. Rank-order correlation coefficients were consistently greater than product-moment correlation coefficients. Job title group summary scores showed higher correlations among electric field indices and magnetic field indices and between electric and magnetic field indices than was found for individual worker-days, with only the 20th percentile clearly independent of the others. These results suggest that individuals' exposures are adequately characterized by a measure of central tendency for electric and magnetic fields, such as the arithmetic or geometric mean, and an indicator of a lower threshold or cutoff for each field type, such as the 20th percentile or proportion of time above 20 V/m or 0.2 microT. A single measure of central tendency for each type of field appears to be adequate when exposures are assessed at the job title level.

Electricity↗