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PubMed2006

Relation between mood and self-reported dry eye in contact lens wearers.

PURPOSE: The etiology of dry eye disease is poorly understood, and a significant percentage of the population reports experiencing frequent and burdensome symptoms. Recent evidence from other disciplines has shown a relation between self-rated mood and symptom reporting, and the purpose of this work was to explore the relation between self-rated mood and dry eye symptoms. METHODS: A cross-sectional/nested case-control study was used to examine factors associated with self-reported dry eye disease. Logistic and linear regression analyses were used to examine the relation between self-reported dry eye and positive and negative affect. All models included age, sex, education, income, race, and marital status, when appropriate. RESULTS: Four hundred fifteen individuals were enrolled in the study. Two thirds were women, and the average age was 30.6 +/- 11.2 (SD) years. Two hundred fifteen (51.8%) self-reported dry eye. The average positive-affect scores were 34.6 +/- 5.9 and 34.9 +/- 6.0 (t = 0.58, P = 0.56) for those self-reporting dry eye and not reporting dry eye, respectively. The average negative-affect scores were 19.4 +/- 6.0 and 18.6 +/- 5.7 (t = -1.38, P = 0.17) for the dry eye and non-dry eye groups, respectively. After controlling for age, neither logistic regression nor linear regression showed a relation between positive or negative affect and self-reported dry eye. CONCLUSION: Preliminary analyses suggest that self-reported mood is not related to dry eye status in contact lens wearers. Although symptoms are a hallmark of dry eye disease, they may not be significant enough such that they relate to affective states in the way they do for other symptomatic diseases with more associated pain (eg, arthritis).

Adult↗

PubMed2004

Association of visual field loss and mobility performance in older adults: Salisbury Eye Evaluation Study.

PURPOSE: To determine the association between visual field loss and orientation and mobility (O&M) performance in a population-based sample of older adults and to identify the specific regions of the visual field that are most strongly associated with O&M performance. METHODS: A population-based sample of 1504 persons between the ages of 72 to 92 was enrolled in the third round of Salisbury Eye Evaluation. Monocular visual fields (60 degrees radius) were tested with the 81-point, single intensity (24 dB) screening test strategy on the Humphrey Field Analyzer. Binocular visual fields were estimated from a combination of the monocular fields. The number of points missed was calculated for the overall visual field and for 3 non-overlapping regions: central (< or = 20 degrees radius), upper- and lower-peripheral visual fields. Orientation and mobility performance was evaluated by walking speed, number of bumps, and number of orientation errors on a circuitous, 32.8-m course seeded with obstacles. Log-linear regressions and linear regressions, adjusting for age, gender, body mass, height, cognitive and general health status, were performed. RESULTS: Loss in the overall visual field was associated with an increase in the number of bumps and decrease in walking speed. Visual field loss was not associated with the number of orientation errors. Out of the three visual field sub-regions that we tested, in terms of percentage of loss, the central and lower peripheral regions showed comparable decrements in walking speed and the central region was most strongly associated with number of bumps. CONCLUSIONS: The loss in visual field, which occurs with aging, is associated with a decline in mobility performance. Walking speed decreases, and the number of bumps into obstacles increases, with decreases in the visual field. The number of orientation errors is not associated with the loss in visual field that occurs with aging.

Aged↗

PubMed1986

Bioavailability of manganese sulfate and manganese monoxide in chicks as measured by tissue uptake of manganese from conventional dietary levels.

The biological availability of reagent grade manganese sulfate and manganese monoxide was determined in broiler chicks fed conventional dietary Mn levels. A basal corn-soybean meal diet (35 ppm Mn) was supplemented with 40, 80, or 120 ppm Mn from the two sources and fed ad libitum for 21 days. There were no differences in average daily feed intake, daily gain, or feed conversion among treatments. There was a linear (P less than .001) increase in bone, kidney, and liver Mn as dietary Mn increased. Manganese monoxide averaged 66% of the availability of manganese sulfate as determined by a combination of linear regression, multiple linear regression and tissue Mn increase. Bioavailability was similar to that obtained when sources were fed at high dietary levels in a previous study.

Animals↗

PubMedDate not supplied

Factors predictive of LASIK flap thickness with the Hansatome zero compression microkeratome.

PURPOSE: To determine the explanatory power of preoperative variables and comeal flap thickness in laser in situ keratomileusis (LASIK) using the Hansatome zero compression microkeratome (Bausch & Lomb, Rochester, NY). METHODS: A prospective, nonrandomized, comparative interventional case study was performed on 250 eyes of 129 consecutive patients who underwent LASIK surgery using the Hansatome zero compression microkeratome. A 160-microm or 180-microm microkeratome head and an 8.5- or 9.5-mm suction ring were used in the procedures. Preoperative measurements included refraction, spherical equivalent, keratometry, intraocular pressure, corneal white-to-white, anterior chamber depth, and corneal eccentricity. Corneal thickness was measured intraoperatively using ultrasonic pachymetry before and after flap creation, and the difference was taken as flap thickness. Flap diameter was measured with a corneal gauge. Data were analyzed using simple, multiple, stepwise linear and non-linear regression analyses and two-tailed t tests. RESULTS: The mean flap thickness was 124 +/- 17 microm with the nominal 160-microm head and 142 +/- 20 microm with the nominal 180-microm head. One third (33%) of the total variation in flap thickness could be accounted for by three preoperative variables: average corneal thickness, spherical equivalent refraction, and choice of 160- or 180-microm microkeratome head. A simple correlation of 0.114 was noted between corneal eccentricity and flap thickness, but this variable did not add significant explanatory power on multiple regression analysis. Linear regression analysis allowed determination of a flap thickness nomogram with a standard error of the estimate of 16.9 microm and a 95% confidence interval of +/- 33.1. CONCLUSIONS: Comeal thickness is the most systematic predictor of corneal flap thickness using the Hansatome microkeratome. Because three preoperative variables account for only 33% of the range in flap thickness, future studies should focus on variations in blade extension and corneal biomechanical factors, which may also play an important role in determining flap thickness.

Adult↗

PubMed1989

Correlation of hematologic recovery with CFU-GM content of autologous bone marrow grafts treated with 4-hydroperoxycyclophosphamide. Culture after cryopreservation.

We previously described an exponential correlation of the CFU-GM content of 4-hydroperoxycyclophosphamide-treated autologous bone marrow grafts and the rate of hematologic recovery of the recipients after transplantation. Those grafts were assayed before cryopreservation. We now describe a similar analysis based upon cultures of the thawed bone marrow. In a proportional hazards model, the CFU-GM content of the grafts sampled after thawing predicted time to achieving a peripheral blood count of 1 X 10(9)/l leukocytes, 0.5 X 10(9)/l granulocytes, 2% reticulocytes, and last platelet transfusion (p less than 0.001). Using linear regression analysis, the logarithm of the CFU-GM content/kg of recipient weight also was correlated with the time to achieving 1 X 10(9)/l leukocytes (r = -0.62), and 0.5 X 10(9)/l granulocytes (r = -0.66). The hazard ratios (Cox model) and regression coefficients (linear regression model) for the equations calculated from the post-thaw cultures were usually smaller than the corresponding coefficients based upon the pre-freeze cultures, suggesting that pre-freeze cultures may be more accurate predictors of aplasia duration. However, patients with poor post-freeze survival of CFU-GM were more likely to experience delayed engraftment. Therefore, the correlation of post-thaw cultures with engraftment may permit the analysis of cryopreservation techniques.

Adolescent↗

PubMed1997

[A method for estimating the prevalence of mammary Staphylococcus aureus and Streptococcus agalactiae infections in herds based on an examination of bulk milk samples].

Parallel quantitative determination executed in 92 herds at 107 sampling dates was focused on the counts of major pathogens (Staphylococcus aureus, Streptococcus agalactiae) in bulk milk samples and on the prevalence of the above pathogens in a herd by examination of individual milk samples. The counts of main pathogens were also determined in terms of quantity in rinsing water before milking and in bulk samples in 5 herds with pipeline milking. Tab. I shows the qualitative analysis of the relation. Sensitivity of the method is satisfactory for the pathogens observed (95% and 91%, resp.), but method is less specific for Staph. aureus (67% against 92% Str. agalactiae). Figs. 1 and 2 show coordinate graphs of the results obtained while Figs. 3 and 4 document the distribution of frequency of the particular values in data sets. The values do not exhibit normal distribution (P < 0.01). Spearman's coefficient of rank correlation of bulk milk and individual examinations amounted to 0.823 and 0.900 for Staph. aureus and Str. agalactiae, respectively. Four mathematical models were tested in the course of quantitative analysis, describing the relation between bulk milk examination and individual examination: (1) linear regression, (2) linear regression with fixed starting point, (3) logarithmic regression and (4) irrational function. A model based on the equation of irrational function (4) was found to be best: y = a + bx + c square root of x + k +/- a1 + i(t)c1 square root of x + k1. Tab. II shows the parameters of the equation for examined microorganisms. Correlation coefficients for the above equation are r = 0.733 and r = 0.842 for Staph. aureus and Str. agalactiae, respectively. Prediction curves (Figs. 5 to 8) and confidence regions of prediction curves were also determined for the best model, and a prediction table was constructed (Tab. III). It was confirmed that the milking machines were not a significant source of direct contamination of bulk milk samples with the examined pathogens (Tab. V).

Animals↗

PubMed1991

The effects of transformations and preliminary tests for non-linearity in regression.

Non-linear relationships between two variables are often detected as a result of a preliminary statistical test for linearity. Common approaches to dealing with non-linearity are to (a) make a linearizing transformation in the independent variable or (b) fit a relationship that is non-linear in the independent variable, such as including a quadratic term. With either approach, the resulting test for association between the two variables can have an inflated type I error. We consider testing the significance of the quadratic term in a quadratic model as a preliminary test for non-linearity. Using simulation experiments and asymptotic arguments, we quantify the type I error inflation and suggest simple modifications of standard practice to protect the size of the type I error. In the case of quadratic regression, the type I error will be increased by roughly 50 per cent. The simple strategy of appropriately correcting the alpha-level is shown to have minimal loss of power if the relationship is truly linear. In the case of a linearizing transformation, the impact on the type I error will depend on the values of the independent variable and on the set of potential linearizing transformations considered. Simulation results suggest that a procedure which adjusts the test statistic according to the results of the preliminary test may offer adequate protection.

Aging↗

PubMed2000

The centercept: an estimable and meaningful regression parameter.

Linear regression is a mathematical model that is employed broadly throughout all of social science research. The choice of parameterization for linear models has important substantive and statistical implications. This article examines the typical parameterization chosen, which includes a parameter for slope and a parameter for the y-intercept. The article demonstrates that the centercept has an interpretive advantage over the traditionally used y-intercept and that the centercept is typically estimated more accurately.

Humans↗

PubMed1998

Impact of resting and ischemic blood flow on infarct probability in ischemic preconditioning--a new approach to infarct size-blood flow data by logistic regression.

The linear regression analysis of infarct size (IS) v ischemic myocardial blood flow (MBF) does not account for the heterogeneity of MBF and infarcted tissue; moreover, it cannot assess a blood flow threshold for infarction (MBFT) accurately, as with ischemic preconditioning (IP) the close relationship between ischemic MBF and IS otherwise observed is lost. Finally, the impact of resting blood flow on myocardial infarction cannot be considered in such analysis. Therefore, in a retrospective data analysis of 32 enflurane-anaesthetized swine undergoing 90 min severe ischemia and 120 min reperfusion without (CON, n = 12) or with IP induced by either 3 (IP3, n = 8) or 10 min ischemia (IP10, n = 12) and 15 min reperfusion, a MBFT was assessed by logistic regression (LR) in individual tissue pieces. MBFT was arbitrarily defined as that ischemic MBF (microspheres) at which infarct probability was 0.2, derived from the ratio of infarcted (n = 141, TTC) to all tissue samples (n = 684). The duration of the preconditioning ischemia and MBF both at rest and during the sustained ischemia were significant predictors of infarct probability. Ischemic MBFT at an infarct probability of 0.2, was 0.089 +/- 0.023 ml/min/g in CON. MBFT was decreased to 0.051 +/- 0.03 ml/min/g with IP3 (P < 0.05 v CON) and further to 0.004 +/- 0.037 ml/min/g with IP10 (P < 0.05 v CON, IP3). Corresponding to the leftward shift of MBFT, the relationships between infarct probability and MBF were shifted in parallel by IP with no change in their slopes.

Animals↗

PubMed1998

Changes in lipid peroxide level in retinal pigment epithelial cells in vitro upon addition of linoleic acids or linoleic acid hydroperoxides under varying concentrations of oxygen.

We previously observed the presence of autofluorescent lipofuscin or its like in retinal pigment epithelial (RPE) cells, which were incubated with linoleic acid hydroperoxides (LHP). We studied the effect of oxygen on the level of lipid peroxides in RPE cells in the presence of linoleic acids (LA) or LHP. The level of lipid peroxides in these cells was determined by use of the thiobarbituric acid-reactive substance (TBARS), which responded to oxygen concentrations qualitatively, and a linear regression analysis. Multiple linear regression analysis disclosed that treatment with LA for 24 hr resulted in detectable increase in the level of TBARS in the cells, whereas treatment with LA or LHP for 48 hr caused detectable decrease. Stepwise linear regression analysis showed that the level of TBARS decreased in an oxygen-tension dependent manner in the cells incubated with LA for 48 hr. Thus, it was shown that short-term incubation with LA increased the level of TBARS in the cells and that LA decreased its level in an oxygen-tension dependent manner. For these results, the postulation was made that the prolonged auto-oxidation of LA caused production of lipofuscin-like materials, a complex of lipid peroxides and proteins that were insoluble in SDS and acetic acid solution.

Animals↗

PubMed2004

A comparison of X-ray fluorescence and wet chemical analysis of air filter samples from a scrap lead smelting operation.

Personal and area air samples were taken at a scrap lead smelter operation in a bullet manufacturing facility. Samples were taken using the 37-mm styrene-acrylonitrile closed-face filter cassette (CFC, the current US standard device for lead sampling), the 37-mm GSP or "cone" sampler, the 25-mm Institute of Occupational Medicine (IOM) inhalable sampler, and the 25-mm Button sampler (developed at the University of Cincinnati). Polyvinylchloride filters were used for sampling. The filters were pre- and post-weighed, and analyzed for lead content using a field-portable X-ray fluorescence (XRF) analyzer. The filters were then extracted with dilute nitric acid in an ultrasonic extraction bath and the solutions were analyzed by inductively coupled plasma optical emission spectroscopy. The 25-mm filters were analyzed using a single XRF reading, while three readings on different parts of the filter were taken from the 37-mm filters. The single reading from the 25-mm filters was adjusted for the nominal area of the filter to obtain the mass loading, while the three readings from the 37-mm filters were inserted into two different algorithms for calculating the mass loadings, and the algorithms were compared. The IOM sampler was designed for material collected in the body of the sampler to be part of the collected sample as well as that on the filter. Therefore, the IOM sampler cassettes were rinsed separately to determine if wall-loss corrections were necessary. All four samplers gave very good correlations between the two analytical methods above the limit of detection of the XRF procedure. The limit of detection for the 25-mm filters (5 microg) was lower than for the 37-mm filters (10 microg). The percentage of XRF results that were within 25% of the corresponding ICP results was evaluated. In addition, the bias from linear regression was estimated. Linear regression for the Button sampler and the IOM sampler using single readings and the GSP using all tested techniques for total filter loading gave acceptable XRF readings at loadings equivalent to sampling at the OSHA 8-hour Action Level and Permissible Exposure Limit. However, the CFC only had acceptable results when the center reading corrected for filter area was used, which was surprising, and may be a result of a limited data set. In addition to linear regression, simple estimation of bias indicated reasonable agreements between XRF and ICP results for single XRF readings on the Button sampler filters, (82% of the individual results within criterion), and on the IOM sampler filters (77% or 61%--see text), and on the GSP sampler filters using the OSHA algorithm (78%). As a result of this pilot project, all three samplers were considered suitable for inclusion in further field research studies.

Air Pollutants, Occupational↗

PubMed1998

Can cerebrovascular reactivity be assessed without measuring blood pressure in patients with carotid artery disease? .

BACKGROUND AND PURPOSE: Conventional methods of assessing cerebrovascular reactivity (CVR) omit the influence of blood pressure (BP). This study demonstrates the significant influence of BP during the assessment of CVR in patients with carotid artery disease. METHODS: In 56 subjects the CVR was bilaterally assessed by measurement of cerebral blood flow velocity change in response to inhalation of 5% CO2 in air while BP was continuously monitored. Three methods of calculating the CVR were used: the conventional ratio between relative cerebral blood flow velocity and end-tidal CO2, simple linear regression, and multiple linear regression analysis (MLRA). The clinical significance of the difference in CVR indices was evaluated. The Bland-Altman test was applied to quantify the comparability and bias between measurements. The magnitude and significance of a change in BP during the CVR assessment were calculated in conjunction with an estimate of the velocity change attributed to the BP. The statistical significance of the data segment length on the variability and magnitude of the CVR index was computed. RESULTS: The value of the CVR index was reduced by 20% and 6% in comparison to the conventional ratio approach when MLRA and linear regression were applied, respectively. With the use of MLRA, in 96% of cases the value of the BP coefficient was statistically significant, and in four patients the increase in velocity was primarily attributed to the increase in BP. CONCLUSIONS: The influence of BP is significant and requires consideration when the CVR index is calculated in patients with carotid artery disease.

Aged↗

PubMedDate not supplied

Influence of age on intrarenal resistive index measurement in normal subjects.

BACKGROUND: We investigated the influence of age on intrarenal arterial resistive index (RI) measurement in 135 normal subjects (71 male, 64 female; age range = 17-68 years, median age = 37 years). METHODS: Each subject underwent color Doppler measurement of the intrarenal RI from three distinct interlobar arteries in the superior, middle, and inferior parts of both kidneys. The mean of six RI values obtained from both kidneys was used for analysis. The correlation of RI with different variables was investigated by linear regression and stepwise multiple linear regression. Variables analyzed were age, systolic blood pressure, diastolic blood pressure, mean blood pressure, pulse pressure, and pulse rate. RESULTS: The results of linear regression showed that age had a significantly positive correlation ( r = 0.276, p = 0.0012) and diastolic blood pressure had a significantly negative correlation ( r = -0.186, p = 0.0311) with the RI. The results of stepwise multiple linear regression showed that the combination of age and diastolic blood pressure could explain approximately 15% of the RI changes ( r(2) = 0.1535). CONCLUSION: Although there is a statistically significant positive correlation between intrarenal RI and age, the correlation is weak. This suggests that the influence of age on RI measurement is small and may be of no clinical importance.

Adult↗

PubMed2003

A comparison of several regression models for analysing cost of CABG surgery.

Investigators in clinical research are often interested in determining the association between patient characteristics and cost of medical or surgical treatment. However, there is no uniformly agreed upon regression model with which to analyse cost data. The objective of the current study was to compare the performance of linear regression, linear regression with log-transformed cost, generalized linear models with Poisson, negative binomial and gamma distributions, median regression, and proportional hazards models for analysing costs in a cohort of patients undergoing CABG surgery. The study was performed on data comprising 1959 patients who underwent CABG surgery in Calgary, Alberta, between June 1994 and March 1998. Ten of 21 patient characteristics were significantly associated with cost of surgery in all seven models. Eight variables were not significantly associated with cost of surgery in all seven models. Using mean squared prediction error as a loss function, proportional hazards regression and the three generalized linear models were best able to predict cost in independent validation data. Using mean absolute error, linear regression with log-transformed cost, proportional hazards regression, and median regression to predict median cost, were best able to predict cost in independent validation data. Since the models demonstrated good consistency in identifying factors associated with increased cost of CABG surgery, any of the seven models can be used for identifying factors associated with increased cost of surgery. However, the magnitude of, and the interpretation of, the coefficients vary across models. Researchers are encouraged to consider a variety of candidate models, including those better known in the econometrics literature, rather than begin data analysis with one regression model selected a priori. The final choice of regression model should be made after a careful assessment of how best to assess predictive ability and should be tailored to the particular data in question.

Aged↗

PubMed2004

Applicational possibilities of linear and non-linear (polynomial) regression and analysis of variance. III. Stability determination of pharmaceutical preparations: stability of diclofenac-sodium in Diclofen injections.

This paper presents the application of the regression analysis program and the program for comparing linear regressions (modified method for one-way, analysis of variance), writtens in BASIC program language, for instance, determination of content of Diclofenac-Sodium (active ingredient in DIKLOFEN injections, ampules á 75 mg/3 ml). Stability testing of Diclofenac-Sodium was done by isothermic method of accelerated aging at 4 different temperatures (30 degrees, 40 degrees, 50 degrees and 60 degrees C) as a function of time (4 different duration of treatment: (0-155, 0-145, 0-74 and 0-44 days). The decrease in stability (decrease in the mean value of the content of Diclofenac-Sodium (in %), at different temperatures as a function of time, is possible to describe by, linear dependance. According to the value for regression equation values, the times are assessed in which the content of Diclofenac-Sodium (in %) will decrease by 10%, of the initial value. The times are follows at 30 degrees C 761.02 days, at 40 degrees C 397.26 days, at 50 degrees C 201.96 days and at 60 degrees C 58.85 days. The estimated times (in days) in which the mean value for Diclofenac-Sodium content (in %) will by 10% of the initial values, as a junction of time, are most suitably described by 3rd order parabola. Based on the parameter values which describe the 3rd order parabola, the time was estimated in which Diclofenac-Sodium content mean value (in %) will fall by 10% of the initial one at average ambient temperatures of 20 degrees C and 25 degrees C. The times are: 1409.47 days (20 degrees C) and 1042.39 days (25 degrees C). Based on the value for Fischer's coefficien (F), the comparison of trenf of Diclofenac-Sodium content (in %) shows that, under the influence of different temperatures as a function of time, among them, depending on temperature value, there is: statistically very significant difference (P << .05) at 50 degrees C and lower toward 60 degrees C, i.e. statistically probably significant difference (P > 0.01) at 40 degrees C and lower towards 50 degrees C and there is no statistically significance difference (P >> 0.05) at 30 degrees C towards 40 degrees C.

Algorithms↗

PubMed2000

Use of a non-linear spline regression to model time-varying fluctuations in mammary-secretion element concentrations of periparturient mares in Michigan, USA.

A study was designed to model the fluctuations of nine specific element concentrations in mammary secretions from periparturient mares over time. During the 1992 foaling season, serial samples of mammary secretions were collected from all 18 pregnant Arabian mares at the Michigan State University equine teaching and research center. Non-linear regression techniques were used to model the relationship between element concentration in mammary secretions and days from foaling (which connected two separate sigmoid curves with a spline function); indicator variables were included for mare and mare parity. Element concentrations in mammary secretions varied significantly during the periparturient period in mares. Both time trends and individual variability explained a significant portion of the variation in these element concentrations. Multiparous mares had lower concentrations of K and Zn, but higher concentrations of Na. Substantial serial and spatial correlation were detected in spite of modeling efforts to avoid the problem. As a result, p-values obtained for parameter estimates were likely biased toward zero. Nonetheless, results of this analysis indicate that monitoring changes in mammary-secretion element concentrations might reasonably be used as a predictor of impending parturition in the mare. In addition, these results suggest that element concentrations warrant attention in the development of neonatal milk-replacement therapies. This study demonstrates that non-linear regression can be used successfully to model time-series data in animal-health management. This approach should be considered by investigators facing similar analytical challenges.

Animal Husbandry↗

PubMed1999

Heart rate monitoring as a field method for estimating energy expenditure as evaluated by the doubly labeled water method.

Energy expenditure (TEE) determined by the doubly labeled water technique (DLW) in 10 adult subjects (5 males and 5 females) was used to evaluate the energy expenditure estimated from 24 h heart rate monitoring records (HR method) for 2 d randomly sampled during 2 weeks of DLW study. Individual data on HR and oxygen consumption, obtained during a step test (resting conditions, and up and down at 3 or 4 stepping rates) and postabsorptive conditions (resting metabolic rate: RMR), were used to calculate three types of calibration regression line, i.e., straight-linear regression (EE-HR: A for TEEhr-A), log-linear regression (lnEE-HR: B for TEEhr-B), and two-linear regression (flex-HR method: C for TEEhr-C). When the 24 h HR records were applied, these calibration regressions provided three estimates of TEE (mean +/- SD kcal/24 h): TEEhr-A (3,059 +/- 1,246 in all subjects), TEEhr-B (2,472 +/- 843), and TEEhr-C (2,759 +/- 1,228). Mean TEE determined by the DLW method (TEEdlw) was 2,544 +/- 378 kcal/24 h. Although no mean values estimated by HR methods were significantly different statistically from the mean value of TEEdlw, the variances of the estimates (e.g., SD) by the HR method were much greater than that of TEEdlw (between twofold and threefold). TEEhr-B estimated by lnEE-HR regression provided the smallest differences from that of TEEdlw (mean difference of -3.1% with a range of -35.1(-)+36.6%). From these observations, the following conclusions were made: 1) The estimates of TEE by HR are useful as a group mean, but interpretation of the individual TEE estimates requires caution because of great deviations from the reference values. 2) Among the calibration methods tested, the log-linear calibration regression (lnEE on HR) gives the best estimates of TEE by the HR method and is recommended for use in future studies.

Adolescent↗

PubMed1995

Effect of dietary sodium on airways responsiveness and its importance in the epidemiology of asthma: an evaluation in three areas of northern England.

BACKGROUND: Although several investigations have shown a relationship between asthma (or its surrogate, airways responsiveness) and dietary or urinary sodium, others have not, and the matter remains controversial. This "salt effect" has been investigated during two recent epidemiological surveys of men in northern England. The first assessed the possible effect on airways responsiveness of occupational exposure to welding fumes, and the second characterised airways responsiveness in two geographically distinct residential areas. Thus, three separate study areas/populations were involved. METHODS: Investigation 1 involved 1059 shipyard workers aged 16-27 years who were exposed variously to welding fumes, and Investigation 2 involved 587 men aged 20-44 years who lived in rural West Cumbria or in urban Newcastle upon Tyne. In Investigation 1, a 24 hour urine specimen was requested from each subject with quantifiable airways responsiveness (PD20 < or = 6400 micrograms methacholine) and from an equal number of subjects without measurable airways responsiveness from the same occupational subgroup. In Investigation 2, every subject was asked to provide a 24 hour urine specimen. RESULTS: Of the men undergoing methacholine tests, satisfactory 24 hour urine specimens were obtained from 234 (22.1%) in Investigation 1 and 232 (39.5%) in Investigation 2. Analysis using multiple linear regression, multiple linear logistic regression, and multiple regression for censored data produced consistent results within each study population but conflicting results between them, such that there was no hint of a relationship between airways responsiveness and 24 hour urinary sodium excretion in the shipyard workers of Investigation 1 nor in the rural West Cumbrian population of Investigation 2, but an association was found in the urban Newcastle population of Investigation 2. All study populations were sufficiently large to demonstrate anticipated relationships between airways responsiveness and atopy, baseline FEV1, and (Newcastle only) age. CONCLUSIONS: If airways responsiveness is related to dietary sodium the relationship is not likely to be strong.

Adolescent↗