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PubMed1996

Prognosis versus actual outcome. II. The effectiveness of clinical parameters in developing an accurate prognosis.

The assignment of prognosis is one of the most important functions undertaken in clinical practice, yet there is little evidence to support the current decision-making process which is based on an outdated model of disease etiology and progression. This study evaluated 100 treated periodontal patients (2,484 teeth) under maintenance care for 5 years, with 38 of these patients followed for 8 years, to determine the relationship of assigned prognoses to the clinical criteria commonly used in the development of prognosis. The method of generalized estimating equations (GEE) for correlated data was utilized to determine the relationship of each clinical factor to the assignment of initial prognosis, improvement in prognosis at 5 years, and worsening in prognosis at 5 years. A multiple linear regression model was constructed for predicting initial prognosis based on initial clinical data. Increased probing depth, more severe furcation involvement, greater mobility, unsatisfactory crown-to-root ratio, malpositioned teeth, and teeth used as fixed abutments resulted in worse initial prognoses. The coefficients from this model were able to predict accurately the 5-year and 8-year prognoses 81% of the time. When teeth with "good" prognoses were excluded, the predictive accuracy dropped approximately 50%. Multiple logistic regression models indicated that improvement in prognoses and worsening in prognoses were both strongly associated with initial probing depth, initial furcation involvement, initial tooth malposition, and smoking when adjusted for initial prognosis. In addition, good hygiene was found to increase the probability of improvement in prognosis while initial mobility was found to decrease the likelihood of improvement in prognosis. Neither of these factors was found to be significant in worsening of prognosis. Smoking decreased the likelihood of improvement by 60% and doubled the likelihood of worsening in prognosis at 5 years. The results of this study indicate that some clinical factors used in the assignment of prognoses are clearly associated with changes in clinical condition over time. The data also demonstrated that the traditional approach for assigning prognoses is ineffective for teeth with an initial prognosis of less than good. Since most periodontally involved teeth are compromised, further work should include the development of a more effective method for assigning prognoses that is based on clear, objective clinical criteria.

Age Factors↗

PubMed2005

The physician as a factor in outpatient medical care after laparoscopically assisted vaginal hysterectomy: a multivariate analysis.

OBJECTIVE: To evaluate whether physician experience affects outpatient medical care utilization after laparoscopically assisted vaginal hysterectomy (LAVH). STUDY DESIGN: A total of 120 patients who underwent LAVH were included in the study; 84 underwent LAVH by 2 senior physicians, who had performed an average of 3 LAVHs per month for >6 years; 36 patients underwent LAVH by 3 junior physicians, who had performed an average of 1 case per month for < 3 years. Data were analyzed by the multiple linear regression model. The dependent variable was the number of outpatient visits within 3 months after discharge. The independent variables were patient age, parity, pelvic adhesions, chronic disease and physicians performing LAVH > 6 years. RESULTS: The patients in the 2 groups did not differ in age, parity, chronic disease or pelvic adhesions. The level of physician experience significantly influenced the mean number of outpatient visits after LAVH within 3 months. After controlling for patient characteristics, the mean number of outpatient visits after discharge within 3 months of LAVH performed by senior physicians with 6 years of experience was reduced (-1.98). CONCLUSION: LAVH performed by experienced physicians reduces the need for patients to seek postoperative outpatient medical care, thereby controlling medical costs incurred under the hospital global budget payment system. However, adding more variables to the multiple regression model, such as the socioeconomic status of patients, habits of seeking medical help, distance between home and hospital and relationship between patient and physician, may further explain the factors affecting outpatient medical care utilization.

Adult↗

PubMed2000

Elevated serum leptin in patients with coronary artery disease: no association with the Trp64Arg polymorphism of the beta3-adrenergic receptor.

BACKGROUND: Serum leptin is associated with the occurrence of cardiovascular risk factors but it is unknown whether leptin is also associated with cardiovascular disease. Another open question is whether the Trp64Arg polymorphism of the beta3-adrenergic receptor (beta3-AR) is a determinant of circulating leptin. OBJECTIVES: We measured serum leptin concentrations in a large group of patients with angiographically assessed coronary artery disease (CAD) and investigated the relationship between the Trp64Arg polymorphism of the beta3-adrenergic receptor (AR) and serum leptin. PATIENTS AND METHODS: Leptin was measured in the fasting state in 1000 consecutive patients with angiographically confirmed CAD by radioimmunoassay. The codon 64 T/C polymorphism of the beta3-AR gene was analysed by the polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) technique. Controls were 1000 age-, gender- and weight-matched subjects without clinical signs of CAD. RESULTS: Serum leptin concentrations were significantly higher in patients with CAD than in those without CAD (median: 6.8 vs 6.1 ng/ml, P < 0.001). In a multiple regression analysis leptin was found to be a determinant of CAD (P = 0.005) along with established risk factors. No differences in serum leptin were observed between wild-type and heterozygous carriers of the Trp64Arg mutation of the beta3-AR gene, whereas the small group of homozygous carriers had higher leptin due to their higher BMI. In a multiple linear regression analysis, body mass index, gender and fasting insulin were the main significant determinants of serum leptin, whereas the beta3-AR polymorphism had no effect. CONCLUSIONS: Patients with coronary artery disease exhibit higher serum leptin concentrations than age- and gender-matched controls of comparable BMI, indicating that leptin could contribute to the development of cardiovascular disease, possibly via activation of the sympathetic nervous system. The Trp64Arg variant of the beta3-adrenoceptor did not influence serum leptin.

Aged↗

PubMed1997

Uroflowmetry in women with urinary incontinence and pelvic organ prolapse.

OBJECTIVE: To characterize uroflowmetry parameters in women with pelvic organ prolapse (POP) and urinary incontinence (UI) and to assess the effects of clinical and urodynamic variables on these parameters. PATIENTS AND METHODS: The study comprised 655 consecutive women who presented with UI or POP and who had interpretable uroflowmetry values. Normal uroflowmetry values were defined as a maximum flow (Q(max)) > or = 15 mL/s, a mean flow (Q(mean)) > or = 10 mL/s, a post-void residual volume (PVR) < or = 100 mL and a continuous, single-peak waveform. Parametric and non-parametric analysis of variance and chi-square analysis were used to compare differences between diagnostic groups. Multiple linear regression models were developed to evaluate factors considered to influence uroflowmetry. RESULTS: Of the 655 patients, 471 (72%) had UI of whom 16% had pure detrusor instability (DI), 69% pure genuine stress incontinence (GSI) and 15% with both, and 184 (28%) had POP, 26% of whom also had DI. Of all patients, 72% had normal uroflowmetry patterns, 13% had multiple peaks and 15% had patterns with interrupted flow; 56% had completely normal uroflowmetry. There were significant differences in uroflowmetry values between the POP and UI groups, with the former having a lower Q(max) and Q(mean) (P < 0.001), larger PVRs (P < 0.001) and a lower percentage of totally normal uroflowmetry (33% and 64%, respectively, P < 0.001). Of patients with POP, 30% had a PVR > 100 mL. Because of the differences, the POP and UI groups were evaluated separately in the regression analysis. In both groups, the most important determinants of flow rate were the volume voided and pressure transmission ratio (PTR). However, when several factors (including age, voided volume, PTR and maximum detrusor pressure with flow and at Q(max)) were included in the model, they accounted for only 23-26% of the variability of flow in the patients with UI and 36-39% of the variability in patients with POP. The subsets of patients with pure DI in both the UI and POP groups had higher PVR volumes than the other subsets. CONCLUSIONS: These results show that the positive correlation between flow rate and voided volume described in normal populations is also observed in women with UI and POP. However, most of the variability in urine flow was not attributable to factors such as age, voided volume and PTR, confirming the complexity of the micturition mechanism. Women with POP had more objective evidence of emptying-phase dysfunction than women with UI, although most emptied their bladders efficiently. Finally, the results suggest that women with DI exhibit dysfunction of both inhibitory and facilitory detrusor control.

Female↗

PubMedDate not supplied

Relationship between health-related quality of life domains and bone status in postmenopausal Japanese women.

OBJECTIVE: To assess the relationship between health-related quality of life domains and bone status, including bone metabolism, in postmenopausal Japanese community women. DESIGN: The study subjects were 88 women who were participants in a screening program for osteoporosis in 2003 without a history of mental disorders, metabolic disorders, smoking, bone fractures, and/or estrogen treatment. The participation rate was 75.9%. The age range was 50 to 68 years (mean, 57), and body mass index (BMI) ranged from 15.7 to 36.6 (mean, 22.4). Health-related quality of life domains were evaluated using the Medical Outcomes Study Short-Form 36 Health Survey, and bone mineral content was measured by quantitative ultrasound of the calcaneus. Serum total osteocalcin and serum N-telopeptide were measured by enzyme-linked immunosorbent assay. Multiple linear regression models were used to study the association of age, BMI, and eight health-related quality of life domains as independent variables in age-corrected bone status and markers of bone turnover as dependent ones. RESULTS: The participants' calcaneal Z scores by quantitative ultrasound ranged from -2.14 to 2.71. The mean Z score was -0.17 (-0.27, -0.07). Multiple regression analysis revealed that BMI (P < 0.05), physical function (P < 0.01), and role-emotional (role limitations caused by emotional problems) (P < 0.01) were factors in increasing bone mineral content. Also, a positive relationship was found between vitality (P < 0.01), social function (P < 0.05), and total osteocalcin. CONCLUSIONS: Although causality is not clear, in addition to low BMI, role limitations due to poor emotional status and low physical function are related to low bone mineral content in postmenopausal Japanese community women. These results imply that when we are concerned about osteoporosis in postmenopausal women, we should pay attention not only to their physical function but also to their psychological state.

Aged↗

PubMed1996

Spirometry of healthy adult South African men. Part II. Interrelationship between socio-environmental factors and 'race' as determinants of spirometry.

AIM: To examine the interaction of socio-environmental background, 'race' and anthropometry on spirometry. METHODS: A study population of white and black bank workers with broadly comparable current socio-economic circumstances was identified. Detailed questionnaires regarding a number of indicators of socio-environmental status (SES) were administered in addition to anthropometric and spirometric measurements. Multiple linear regression analyses were performed. The Kappa statistic was used to determine the best predictors of SES. RESULTS: 'Race' was found to be the best predictor of SES. Within the black group a sub-classification of high and low SES was possible. In all respects the white SES indicators were higher than those of the black high SES group. Multiple regression analysis showed that sitting height was a better anthropometric predictor of spirometry than standing height. Replacing 'race' with other indicators of SES gave similar measures of prediction (by Mallow's CP statistic) of spirometry in the over-30-year age group. CONCLUSION: The impact of 'race' on spirometry can be reduced substantially by incorporating sitting height and indicators of SES in the regression equations. This observation lends support to the hypothesis that 'race' is not a direct genetic predictor of lung size, but may have an influence because of SES and anthropometric features associated with 'race'.

Adult↗

PubMed2000

Mental maze solving.

We sought to determine how a visual maze is mentally solved. Human subjects (N = 13) viewed mazes with orthogonal, unbranched paths; each subject solved 200-600 mazes in any specific experiment below. There were four to six openings at the perimeter of the maze, of which four were labeled: one was the entry point and the remainder were potential exits marked by Arabic numerals. Starting at the entry point, in some mazes the path exited, whereas in others it terminated within the maze. Subjects were required to type the number corresponding to the true exit (if the path exited) or type zero (if the path did not exit). In all cases, the only required hand movement was a key press, and thus the hand never physically traveled through the maze. Response times (RT) were recorded and analyzed using a multiple linear regression model. RT increased as a function of key parameters of the maze, namely the length of the main path, the number of turns in the path, the direct distance from entry to termination, and the presence of an exit. The dependence of RT on the number of turns was present even when the path length was fixed in a separate experiment (N = 10 subjects). In a different experiment, subjects solved large and small mazes (N = 3 subjects). The former was the same as the latter but was scaled up by 1.77 times. Thus both kinds of mazes contained the same number of squares but each square subtended 1.77 degrees of visual angle (DVA) in the large maze, as compared to 1 DVA in the small one. We found that the average RT was practically the same in both cases. A multiple regression analysis revealed that the processing coefficients related to maze distance (i.e., path length and direct distance) were reduced by approximately one-half when solving large mazes, as compared to solving small mazes. This means that the efficiency in processing distance-related information almost doubled for scaled-up mazes. In contrast, the processing coefficients for number of turns and exit status were practically the same in the two cases. Finally, the eye movements of three subjects were recorded during maze solution. They consisted of sequences of saccades and fixations. The number of fixations in a trial increased as a linear function of the path length and number of turns. With respect to the fixations themselves, eyes tended to fixate on the main path and to follow it along its course, such that fixations occurring later in time were positioned at progressively longer distances from the entry point. Furthermore, the time the eyes spent at each fixation point increased as a linear function of the length and number of turns in the path segment between the current and the upcoming fixation points. These findings suggest that the maze segment from the current fixation spot to the next is being processed during the fixation time (FT), and that a significant aspect of this processing relates to the length and turns in that segment. We interpreted these relations to mean that the maze was mentally traversed. We then estimated the distance and endpoint of the path mentally traversed within a specific FT; we also hypothesized that the next portion of the main path would be traversed during the ensuing FT, and so on for the whole path. A prediction of this hypothesis is that the upcoming saccade would land the eyes at or near the locus on the path where the mental traversing ended, so that "the eyes would pick up where the mental traversal left off." In this way, a portion of the path would be traversed during a fixation and successive such portions would be strung together closely along the main path to complete the processing of the whole path. We tested this prediction by analyzing the relations between the path distance of mental traverse and the distance along the path between the current and the next fixation spot. (ABSTRACT TRUNCATED)

Adult↗

PubMed1998

Relationships of lead in breast milk to lead in blood, urine, and diet of the infant and mother.

We have obtained stable lead isotope and lead concentration data from a longitudinal study of mobilization of lead from the maternal skeleton during pregnancy and lactation and in which the newly born infants were monitored for 6 months postpartum to evaluate the effects of the local environment on lead body burden of the infant. Samples of maternal and infant blood, urine, and diet and especially breast milk were measured for 21 mothers and 24 infants. Blood lead concentrations were less than 5 microg/dl in all except one subject. The mean lead concentration in breast milk +/- standard deviation was 0.73 +/- 0.70 microg/kg. In seven subjects for whom serial breast milk sampling was possible, the lead concentration varied by factors of from 2 to 4, and for three subjects there was an increase at or after 90 days postpartum. For the first 60-90 days postpartum, the contribution from breast milk to blood lead in the infants varied from 36 to 80%. Multiple linear regression analyses indicated statistically significant relationships for some of the variables of isotope ratios and lead concentrations between breast milk, blood, urine, and diet for infants and mothers. For example, the analyses revealed that both a mother's breast milk 207Pb/206Pb and 206Pb/204Pb ratios and lead concentration provide information to predict her infant's blood 207Pb/206Pb and 206Pb/204Pb ratios. The major sources of lead in breast milk are from the maternal bone and diet. An evaluation of breast milk lead concentrations published over the last 15 years indicates that studies in which the ratio of lead concentrations in breast milk to lead concentrations in whole maternal blood (Multiple>100) were greater than 15 should be viewed with caution because of potential contamination during sampling and/or laboratory analyses. Selected studies also appear to show a linear relationship between breast milk and maternal whole blood, with the percentage of lead in breast milk compared with whole blood of <3% in subjects with blood lead levels ranging from 2 to 34 microgram/dl. The levels of lead in breast milk are thus similar to those in plasma. Breast-fed infants are only at risk if the mother is exposed to high concentrations of contaminants either from endogenous sources such as the skeleton or exogenous sources.

Adult↗

PubMed1997

Abdominal fat determines growth hormone-binding protein levels in healthy nonobese adults.

The circulating high affinity GH-binding protein (GHBP), which derives from the extracellular domain of the hepatic GH receptor, correlates inversely to GH levels and directly to body mass index (BMI) in healthy adults. As GH secretion and adiposity are also interrelated, we tested the hypothesis that body composition more than GH, determines GHBP levels in healthy adults. Forty-two healthy adults [21 females and 21 males; mean age, 39.4 yr range, 27-59 yr); mean BMI, 23.9 kg/m2 (range, 18.9-34.7 kg/m2)], underwent anthropometric measurements (BMI, W/H ratio, computed tomography scan, dual energy x-ray absortiometry (DEXA) scan, and bioimpedance) in addition to two GH stimulation tests (arginine and clonidine) and a 24-h GH profile. By simple linear regression, serum GHBP correlated positively to several indices of adiposity: intraabdominal fat (r = 0.537; P = 0.001), sc abdominal fat (r = 0.680; P < 0.001), BMI (r = 0.483; P = 0.001), W/H ratio (r = 0.452; P = 0.003), total body fat (DEXA scanning; r = 0.503; P = 0.002), and body fat (bioimpedance; r = 0.354; P = 0.023). Lean body mass estimated by DEXA scan was negatively associated with GHBP (r = 0.541; P < 0.001). GHBP was inversely proportional to arginine-stimulated GH release (r = -0.346; P = 0.027) and negatively associated with several measures of spontaneous GH release as estimated by deconvolution analysis (GH mass, GH production rate, and mean GH; r = -0.371; P = 0.017, r = -0.393; P = 0.011, and r = -0.343; P = 0.028, respectively)). With multiple linear regression analyses, indices of adiposity were significant determinants of GHBP levels, whereas GH status did not contribute independently to the prediction of GHBP. Neither insulin-like growth factor I nor fasting insulin levels correlated to GHBP levels. In conclusion, GHBP levels in normal adults seem to be determined by abdominal fat mass rather than GH secretion.

Abdomen↗

PubMed2000

Multiple sites in HIV-1 reverse transcriptase associated with virological response to combination therapy.

OBJECTIVE: To determine whether analysis of sequence variation in reverse transcriptase at baseline can explain differences in response to combination antiretroviral therapy. METHODS: Amino acid sequences of reverse transcriptase obtained from baseline isolates from 55 patients included in a trial of zidovudine and didanosine versus zidovudine/didanosine/nevirapine (ACTG241) were analysed. Simple and multiple linear regression were used to determine the relationship between numbers and identity of mutations at baseline and virological response after 8 and 48 weeks. RESULTS: Numbers of baseline zidovudine resistance mutations were predictive of short-term response (week 8). Amino acid identity at position 215 explained > 20% of the variation in response at week 8, but less at week 48. Multiple regression identified the combinations: 215 + 44 and 41 + 202, each of which explained about 30% of the variation in week 8 response. A model incorporating amino acids 214 + 215 + 60 + 202 + baseline viral load explained > 40% of the variation in response at week 48. Unexpectedly, the mutant combination 601 + 215Y/F responded threefold better than 60V + 215Y/F over 48 weeks. CONCLUSIONS: Use of clinical data to analyse virological response to combination therapy has revealed effects of baseline amino acid mutations at sites not previously identified as being important in antiretroviral resistance. Predictors of long-term responses were different from those involved in the short term and may require more complex analysis.

Acquired Immunodeficiency Syndrome↗

PubMed1990

Energy exchange of two breeds of hens in respiration chambers.

The heat production for two breeds of laying hens was estimated by indirect respiration calorimetry. Using multiple linear regression techniques, egg energy output was identified as a significant contributor to variability in heat production (P = .0113). Heat production of the hens decreased with increasing egg energy output. Body weight, feed intake, egg energy output, and genetic stock were all significant contributors to variability in heat production. Comparisons of traditional techniques (relating energy balance to metabolizable energy intake) and multiple regression techniques (heat production as a function of body weight, feed intake, egg energy output, and genetic stock) for evaluating calorimetry data were made.

Animals↗

PubMed2005

Non-linear quantitative structure-activity relationship for adenine derivatives as competitive inhibitors of adenosine deaminase.

Logistic regression and artificial neural networks have been developed as two non-linear models to establish quantitative structure-activity relationships between structural descriptors and biochemical activity of adenosine based competitive inhibitors, toward adenosine deaminase. The training set included 24 compounds with known k(i) values. The models were trained to solve two-class problems. Unlike the previous work in which multiple linear regression was used, the highest of positive charge on the molecules was recognized to be in close relation with their inhibition activity, while the electric charge on atom N1 of adenosine was found to be a poor descriptor. Consequently, the previously developed equation was improved and the newly formed one could predict the class of 91.66% of compounds correctly. Also optimized 2-3-1 and 3-4-1 neural networks could increase this rate to 95.83%.

Adenine↗

PubMed1994

Determination of left ventricular mass by echocardiography in a normal population: effect of age and sex in addition to body size.

OBJECTIVE: In this study, we determined the effect of age, sex, and body size on left ventricular mass. DESIGN: Two-dimensional-guided M-mode echocardiography was used in an assessment of 111 healthy, normal adults. MATERIAL AND METHODS: Left ventricular mass was calculated with the cube function formula corrected by a regression equation to agree with autopsy estimates of left ventricular mass. Calculated left ventricular mass, indexed by body surface area and by height, was analyzed on the basis of sex and age of the study participants. Age was analyzed as a dichotomous, trichotomous, and continuous variable. The effects of age, sex, and obesity, as well as interactions, were tested within a multiple linear regression model framework. RESULTS: Left ventricular mass, when indexed for either body surface area or height, was greater in men than in women. For women, but not men, we found a small but significant increase in left ventricular mass with advancing age. Body mass index, an indicator of obesity, increased with aging in women but not in men and affected left ventricular mass. No significant changes were noted in left ventricular cavity size with advancing age, and the increase in left ventricular mass in women was due to increased ventricular wall thickness. CONCLUSION: The findings in this study suggest that left ventricular mass, as assessed by two-dimensional-guided M-mode echocardiography, is affected not only by sex and body size but also by age in women. This phenomenon may be related to an increase in body mass index with advancing age in women. In clinical studies that use echocardiographic left ventricular mass to diagnose left ventricular hypertrophy, these observations should be considered.

Activities of Daily Living↗

PubMed1990

Analysis of variables of plasmid transformation of a bacterial vaccine: studies on recombinant BCG.

Stepwise regression analysis was applied to evaluate the strength order of the effect of five explanatory variables on the transformation of BCG substrains by electroporation with hybrid shuttle plasmid [pAL5000:pIJ666] and derived as YUB plasmids containing a kanamycin resistance selection marker. From 66 successful transformations, data of 42 transformations of the Pasteur 1172P2 BCG substrain are analysed. The estimated parameters in the multiple linear regression model show that the association of the explanatory variables with the explained variable, i.e. the efficiency of the transformation of BCG expressed in c.f.u./microgram DNA, in decreasing strength order is: concentration of the plasmid DNA; viability of the non-electroporated concentrated BCG suspensions; viability of the BCG cultures; age of the BCG cultures; and time constant of the electroporation. More extended analysis of other factors of the transformation will improve objective statistical inference regarding the biophysical and molecular biological interpretation of the transformation mechanism by electroporation of the different bacterial species. More precise understanding of optimal conditions of genetic transformation will be particularly important for developing recombinant BCG vaccines.

BCG Vaccine↗

PubMed2003

Sources and concentrations of indoor nitrogen dioxide in Barcelona, Spain.

Sources and concentrations of indoor nitrogen dioxide (NO2) were examined in Barcelona, Spain, during 1996-1999. A total of 340 dwellings of infants participating in a hospital-based cohort study were selected from different areas of the city. Passive filter badges were used for indoor NO2 measurement over 7-30 days. Dwelling inhabitants completed a questionnaire on housing characteristics and smoking habits. Data on outdoor NO2 concentrations were available for the entire period of the study in the areas of the city where indoor concentrations were determined. Bivariate analysis was performed to investigate relationships between indoor NO2 concentrations on one hand and outdoor NO2 concentrations, housing, and occupant characteristics on the other. Stepwise multiple linear regression was performed with variables that were found to have a significant bivariate relationship. Indoor NO2 mean values ranged between 23.57 ppb in 1996 and 27.02 ppb in 1999, with the highest yearly value of 27.82 ppb in 1997. In the same time period, mean outdoor NO2 concentration ranged between 25.26 and 25.78 ppb with a peak of 30.5 ppb in 1998. Multiple regression analysis showed that principal sources of indoor NO2 concentrations were the use of a gas cooker, the absence of an extractor fan when cooking, and cigarette smoking. The absence of central heating was also associated with higher NO2 concentrations. Finally, each ppb increase in outdoor NO2 was associated with a 1% increase in indoor concentrations.

Air Pollution, Indoor↗

PubMed1993

Interval mapping of multiple quantitative trait loci.

The interval mapping method is widely used for the mapping of quantitative trait loci (QTLs) in segregating generations derived from crosses between inbred lines. The efficiency of detecting and the accuracy of mapping multiple QTLs by using genetic markers are much increased by employing multiple QTL models instead of the single QTL models (and no QTL models) used in interval mapping. However, the computational work involved with multiple QTL models is considerable when the number of QTLs is large. In this paper it is proposed to combine multiple linear regression methods with conventional interval mapping. This is achieved by fitting one QTL at a time in a given interval and simultaneously using (part of) the markers as cofactors to eliminate the effects of additional QTLs. It is shown that the proposed method combines the easy computation of the single QTL interval mapping method with much of the efficiency and accuracy of multiple QTL models.

Chromosome Mapping↗

PubMedDate not supplied

The association of airways responsiveness to respiratory symptom prevalence and to pulmonary function in a random population sample.

In a random population sample of 1905 subjects we studied the occurrence of respiratory symptoms in relation to airways responsiveness. Responders (PC10 FEV1 to histamine at 16 mg.ml-1 or less) had crude prevalence rates two to three times higher than nonresponders. In logistic regression analysis, odds ratios were estimated for each threshold value, compared to the reference value (greater than 32 mg.ml-1), controlling for age, sex, area of residence, and smoking habit. Odds ratios increased with decreasing threshold values in a dose-response relationship for all symptoms, except for bronchitis periods. We analysed the association of airways responsiveness to pulmonary function level by multiple linear regression, controlling for age, sex, height, area of residence, and smoking habit. There was an inverse relationship of FEV1 level to threshold value. Male subjects within a threshold value of 1 mg.ml-1 had a mean adjusted FEV1 of 1170 ml less than males with a threshold value of greater than 32 mg.ml-1. The relationship of responsiveness to decline of FEV1 with time was studied in 186 male subjects who took part in five consecutive surveys from 1967 to 1981. The greatest mean adjusted yearly decline was noted in responding smokers: 35.3 ml per yr, compared to nonreactive nonsmokers: 10.9 ml per yr. Regression analysis of the yearly decline in 169 subjects with at least two pairs of two consecutive threshold tests revealed that the more positive tests subjects had, the greater was their mean adjusted yearly decline. It is concluded that airways responsiveness may be an important factor in the development of chronic obstructive pulmonary disease.

Adult↗

PubMed2006

Impact of the time rate of blood pressure variation on left ventricular mass.

OBJECTIVES: Blood pressure (BP) changes are steeper in hypertensive than in normotensive individuals, whereas an increased rate of BP fluctuations is associated with medial hypertrophy of the carotid arteries. We evaluated the association between the rate of BP variation derived from ambulatory blood pressure monitoring (ABPM) data analysis and left ventricular mass (LVM). METHODS: ABPM and echocardiographic measurements of LVM were performed in 365 normotensive, 185 white-coat hypertensive (WCH) and 448 uncomplicated hypertensive individuals. RESULTS: The daytime and night-time rate of systolic blood pressure (SBP) and diastolic BP variation were significantly higher in hypertensive than in normotensive (P < 0.001) and WCH (P < 0.05) individuals. In the entire study population multiple linear regression models revealed independent determinants of LVM in the following rank order: body mass index (beta + 0.266, P < 0.001), daytime SBP (beta + 0.264, P < 0.001), male sex (beta +0.220, P < 0.001), age (beta + 0.203, P < 0.001), daytime heart rate (HR; beta - 0.191, P < 0.001), daytime rate of SBP variation (beta + 0.167, P < 0.001), and SBP dipping (beta - 0.132, P < 0.001). A 0.1 mmHg/min increase in the daytime rate of SBP variation correlated with an increment of 7.087 g (95% confidence interval 4.775-9.399) in the LVM. The addition of the daytime rate of SBP variation in the multiple regression model for the prediction of LVM significantly increased the adjusted model R [R change 0.024 (2.4%); P for change < 0.001]. CONCLUSION: Steeper BP variations may produce a greater stress on the left ventricular wall and may have an additive role to body habitus, BP and HR levels in the detection of cardiac hypertrophy. Target-organ damage in hypertensive patients, in addition to BP levels, dipping status and BP variability, may also be related to a steeper rate of BP oscillations.

Adult↗