DEFINING THE PREVALENCE OF HEART DISEASE IN AN EXAMINATION SURVEY.
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Diagnosis↗
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Results for “statistical physics”
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Testing a model of physical activity and obesity tracking from youth to adulthood: the cardiovascular risk in young Finns study.
OBJECTIVE: To test a potential model of the relationship between physical activity and obesity from youth to adulthood. DESIGN: Longitudinal study data from the cardiovascular risk in young Finns study. SUBJECTS: A total of 1319 boys (n=626) and girls (n=693) aged 9, 12, 15 and 18 years were randomly selected from five university towns and their rural surroundings in 1980. They were followed up for 21 years. In 2001 they were 30, 33, 36 and 39 years old. MEASUREMENTS: Physical activity was assessed by a short questionnaire at two measurement points. Obesity was measured by body mass index (BMI) and sum of skinfolds in 1980 and BMI and waist circumference in 2001. RESULTS: Structural equation analysis (LISREL) indicated that the prevalence of abdominal obesity in adulthood was directly affected by adult physical activity (beta (beta)=-0.16, t=-4.02, P< 0.05 for men, beta=-0.12, t=-3.35, P<0.05 for women) and indirectly via youth physical activity (beta=-0.10, t=-4.68, P< 0.05 for men, beta=-0.07, t=-4.54, P<0.05 for women). Obesity tracked significantly from youth to adulthood (beta=0.41, t=11.13, P<0.05 for men, beta=0.34, t=9.39, P<0.05 for women). Youth physical activity might reduce body weight in youth but was not directly associated with adult abdominal obesity in either men or women. The model accounted 19% of abdominal obesity in men and 13% in women. The path from youth physical activity to adult obesity through youth obesity seemed to be stronger than the path through adult physical activity. CONCLUSIONS: This study lends general support to the hypothesized model that abdominal obesity in adulthood is directly related to adult physical activity and youth overall obesity in both sexes. Youth physical activity had an indirect effect on abdominal obesity through the maintenance of physical activity in adulthood. Participation in and maintaining physical activity from youth to adulthood may have an important role in reducing obesity in adulthood.
Adolescent↗
Ab initio protein folding.
Ab initio protein folding methods have been developing rapidly over the past few years and, at the last Critical assessment of methods of protein structure prediction (CASP) meeting, it was shown that important progress has been made in generating structure from sequence. Both methods based on statistical potentials and methods using physics-based potentials have shown improvements. Most current methods use statistics-based potentials and the development of these is ongoing. Additionally, the inclusion of multiple sequence data in the algorithms in order to aid in finding the native structure is a common theme. The use of physics-based potentials is less developed, which means that less progress has been made in understanding why a sequence forms a structure.
Animals↗
Evaluation of health-related quality of life in low-income patients with COPD receiving long-term oxygen therapy.
STUDY OBJECTIVE: To assess health-related quality of life (HRQL) in a low-income population of patients with hypoxemia and COPD receiving long-term oxygen therapy (LTOT). DESIGN: Cross-sectional study. SETTING: Large, tertiary care, university teaching hospital. PATIENTS OR PARTICIPANTS: Thirty-six patients with COPD requiring LTOT (mean age, 63.5 years; mean FEV(1), 32.1% of predicted; PaO(2), 50.2 mm Hg) and 33 control subjects with COPD but no severe hypoxemia (mean age, 63.1 years; FEV(1), 35.7%; PaO(2), 66.5 mm Hg). INTERVENTIONS: Patients underwent pulmonary function testing to assess physiologic function and the degree of respiratory impairment. A baseline dyspnea index (BDI) was used to determine levels of dyspnea, and a 6-min walk test was performed to evaluate physical performance and exercise capacity. The St. George Respiratory Questionnaire (SGRQ) and the Medical Outcomes Study Short-Form 36-item questionnaire (SF-36) were used to assess health status and HRQL. MEASUREMENTS AND RESULTS: The scores on the SGRQ and SF-36 indicated severe impairment. Patients receiving LTOT showed a trend toward worse scores on most dimensions of the SGRQ and SF-36, but differences between groups were only statistically significant for the physical functioning and social functioning dimensions of the SF-36. Dyspnea, as measured by the BDI, significantly correlated with all questionnaire domains except the SF-36 pain index. CONCLUSIONS: The HRQL of these low-income patients with COPD was markedly impaired, with more pronounced impairment in those receiving LTOT. The severity of dyspnea was a significant predictor of various components of quality of life in these patients.
Cross-Sectional Studies↗
WORK AND THE HEART: ANTICIPATION AND ERGONOMETRY.
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Heart↗
Seven-year change in graded exercise treadmill test performance in young adults in the CARDIA study. Cardiovascular Risk Factors in Young Adults.
PURPOSE: Most studies of physical fitness change have been relatively small, not population-based, and lacking in women and nonwhites. The purpose of this analysis was to evaluate the 7-yr change in physical fitness in a biracial (black and white) population of young men and women. METHODS: We evaluated change in exercise treadmill test performance in a biracial (black and white) population of 1,962 young adults, ages 18-30 yr at baseline, who completed symptom-limited graded exercise treadmill tests at the baseline (1985-1986) and year 7 (1992-1993) examinations of the CARDIA study. RESULTS: Mean test duration decreased 58 s (9.5%) over 7 yr (black men, 13.6% decrease, white men, 7.4%; black women, 11.1%; white women, 7.0%). Mean time to heart rate 130 (WL130), a measure of submaximal performance, decreased 31 s (11.3%) (black men, 16.9%; white men, 10.0%; black women, 12.3%; white women, 6.1%). Baseline body mass index (BMI) and physical activity were not statistically significant predictors of test duration change in any race-gender group, but change in BMI and activity were. Seven-year weight gain >20 lbs (31% of cohort) was associated with a large decrease in fitness (18.5% decrease in mean duration, 21.8% decrease in WL130). CONCLUSION: These data suggest that fitness declines during young adulthood in blacks and whites and that fitness changes are related to changes in weight and physical activity.
Adult↗
EVALUATION OF FAR INFRARED RELATIONS TO ODOR BY A STANDARDS SIMILARITY METHOD.
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Chemical Phenomena↗
The OR control system of bacteriophage lambda. A physical-chemical model for gene regulation.
A quantitative model has been developed for processes in the bacteriophage lambda that control the switchover from lysogenic to lytic modes of growth. These processes include the interactions of cI repressor and cro proteins at the three DNA sites of the right operator, OR, the binding of RNA polymerase at promoters PR and PRM, the synthesis of cI repressor and cro proteins, and the degradative action of recA during induction of lysis. The model is comprised of two major physical-chemical components: a statistical thermodynamic theory for relative probabilities of the various molecular configurations of the control system; and a kinetic model for the coupling of these probabilities to functional events, including synthesis of regulatory proteins cI and cro. Using independently evaluated interaction constants and rate parameters, the model was found capable of predicting essential physiological characteristics of the system over an extended time. Sufficiency of the model to predict known physiological properties lends credence to the physical-chemical assumptions used in its construction. Several major physiological characteristics were found to arise as "system properties" through the non-linear, time-dependent, feedback-modulated combinations of molecular interactions prescribed by the model. These include: maintenance of the lysogenic state in the absence of recA-mediated cI repressor degradation; induction of lysis and the phenomenon of subinduction; and autogenous negative control of cro. We have used the model to determine the roles, within the composite system, of several key molecular processes previously characterized by studies in vitro. These include: co-operativity in cI repressor binding to DNA; interactions between repressors and RNA polymerase (positive control); and the monomer-dimer association of cI repressor molecules. A major role of cI repressor co-operativity is found to be that of guaranteeing stability of the lysogenic state against minor changes in cI repressor levels within the cell. The role of positive control seems to be that of providing for a peaked, rather than monotonic, dependence of PRM activity on cI repressor level, while permitting PR activity to be a step function. The model correlates an immense body of studies in vivo and in vitro, and it makes testable predictions about molecular phenomena as well as physiological characteristics of bacteriophage lambda. The approach developed in this study can be extended to include more features of the lambda system and to treat other systems of gene regulation.
Allosteric Regulation↗
Renal cryoablation in a canine model.
OBJECTIVES: To assess the potential safety and utility of cryoablation for treatment of selected renal tumors in a canine model. METHODS: Ultrasound and direct physical measurements (depth and width) of five cryolesions were compared. Cryolesions were examined histologically in 6 animals, which were killed at 4 hours, 2 days, 1 week, 3 weeks, 6 weeks, and 12 weeks. Mortality/morbidity was assessed in 12 animals over a 1-month interval, where 6 animals received small (approximately 2 cm) cryolesions and 6 animals received large (one third to one half of kidney) cryolesions. Laparoscopic cryoablation was performed in 2 animals. RESULTS: A statistically significant association of physical and ultrasound dimensions was observed (correlation coefficient R = 0.9295; P = 0.0001). Histologic studies in animals killed up to 1 week after cryoablation revealed complete coagulative necrosis within the cryolesion. The boundary transition from normal to complete tissue necrosis occurred in 1 to 2 mm. Animals killed 3 weeks to 3 months after cryoablation revealed progressive organization with granulation tissue, chronic inflammation, hemosiderosis, fibrosis, and contraction of the cryolesion with parenchymal loss. Untreated renal tissue was histologically normal in all kidneys. No mortality or morbidity was detected in the 12 animals followed for 30 days regardless of the size of the cryolesion. Laparoscopic cryoablation was performed successfully in 2 animals without modification of standard laparoscopic methods. CONCLUSIONS: Sonographic, histologic, and laparoscopic data in a canine model suggest that cryoablation may be a safe, feasible, and useful method for treatment of selected renal neoplasms.
Animals↗
Bayesian analysis of systems with random chemical composition: renormalization-group approach to Dirichlet distributions and the statistical theory of dilution.
We investigate the statistical properties of systems with random chemical composition and try to obtain a theoretical derivation of the self-similar Dirichlet distribution, which is used empirically in molecular biology, environmental chemistry, and geochemistry. We consider a system made up of many chemical species and assume that the statistical distribution of the abundance of each chemical species in the system is the result of a succession of a variable number of random dilution events, which can be described by using the renormalization-group theory. A Bayesian approach is used for evaluating the probability density of the chemical composition of the system in terms of the probability densities of the abundances of the different chemical species. We show that for large cascades of dilution events, the probability density of the composition vector of the system is given by a self-similar probability density of the Dirichlet type. We also give an alternative formal derivation for the Dirichlet law based on the maximum entropy approach, by assuming that the average values of the chemical potentials of different species, expressed in terms of molar fractions, are constant. Although the maximum entropy approach leads formally to the Dirichlet distribution, it does not clarify the physical origin of the Dirichlet statistics and has serious limitations. The random theory of dilution provides a physical picture for the emergence of Dirichlet statistics and makes it possible to investigate its validity range. We discuss the implications of our theory in molecular biology, geochemistry, and environmental science.
Algorithms↗
Transition through stages of smoking: the effect of gender and self-concept on adolescent smoking behavior.
PURPOSE: To determine whether self-concept, gender, and age are significant factors in an adolescent's transition through stages of smoking to regular smoking. METHODS: A questionnaire composed of 29 items (nine questions pertaining to smoking behavior and 20 to four self-concept variables: physical, family, social, and peer self-concept) was administered to 368 randomly selected high school adolescents (188 males and 180 females) aged 12-17 years during regular contact (roll call) time. RESULTS: Overall, 40.5% of the sample had tried tobacco (excluding chewing tobacco) (42.8% of females and 38.3% of males). Although prevalence of smoking varied according to the stage of smoking, it increased with age. With reference to self-concept, Scheffe post hoc contrasts revealed a statistically significant difference between physical self-concept and the remaining measures of self-concept (peer, family, and social) and at each stage of smoking. The effect for male students was less than for females. CONCLUSION: Programs aimed at prevention and intervention should incorporate strategies which are commensurate with female lifestyles and the more positive aspects that individuals might experience on quitting.
Adolescent↗
[Treatment of the sick elderly in households accommodating several generations].
Multigenerational households with widowed persons aged 70 and more have been studied in order to determine the relationship between the following two groups of variables: (a) variables in the aged person describing the existence and degree of an organic mental impairment due to a dementive process and of other signs of physical illnesses. (b) variables in her daughter or daughter in law consisting of selfratings of psychosomatic complaints and of attitude-scales. Results were as follows: (a) If there were indications of personality changes due to an organic brain syndrom the relatives had a lower degree of life-satisfaction and more frequently suffered from psychosomatic symptoms and interpersonal stress than those, whose old relatives showed an unaltered personality. (b) A great number of comparisons failed to show any statistical differences. Especially severe physical illness, organic brain syndrome and the need for physical care were not related to life satisfaction, psychosomatic complaints, stress due to emotional involvement and the attitude towards home-care. Our attempt to explain the missing correlations led to the following factors: the small size of the sample, self-selection of the sample and possibly inappropriate operationalisation and measurement of variables. In respect to these results the ongoing study will be modified in some details: There will be a qualitative analysis of transcribed semi-structured interviews. The proportion of families with severely demented relatives will be increased. In an additional step we shall examine families, who have decided to transfer their old member into an institution.
Aged↗
Nonparametric testing using the chi-square distribution.
We have described three separate uses of the chi-square distribution: comparing observed and expected frequency distributions of a nominal variable, testing for the independence of two variables, and using the chi-square test in determining correlation coefficients. We hope this paper has helped you gain an understanding of the uses of the chi-square test and the steps required to calculate this statistic.
Humans↗
[Multidimensional classification of physical development of young people].
The program complex "Status" based on the methods of multidimensional statistics, for the classification of the physical development of young people was worked up. 610 persons were examined and classified to 14 groups by this method.
Adolescent↗
Dietary restriction of adult male rhesus monkeys: design, methodology, and preliminary findings from the first year of study.
Dietary restriction (DR) retards aging processes and extends maximum life span in rodents and in simpler animals. We initiated a study in 30 adults (8-14 years old) male rhesus monkeys to determine whether or not aging processes are retarded by adult-onset DR in a primate species and herein report results from the experiment's first year. Following a 3-6 month period when baseline data were obtained, 15 animals were assigned to a control group and given free access to a semipurified diet for 6-8 hours per day. The other 15 monkeys were fed the same diet but at 70% of their baseline intake levels predetermined individually. The animals are being evaluated semi-annually for body size and composition, physical activity, metabolic rate, glucose tolerance and insulin sensitivity, hematologic indices, immunologic function, and fingernail growth. Ocular function is assessed annually. The preliminary observations after one year are: (a) all monkeys appear to be in excellent health; (b) average body weights for controls increased by 9% while monkeys on DR did not gain weight; (c) monkeys on DR have less body fat than do control monkeys, whereas the amount of lean body mass has not been significantly influenced by DR; (d) there was a small but statistically significant reduction in physical activity for monkeys on DR relative to controls; and (e) DR has not overtly influenced the other measures. Control monkeys gradually reduced their voluntary levels of food intake during the first year of study, and food allotments to DR monkeys are being adjusted accordingly in order to reinstate the intended 30% difference between groups. These early data indicate that DR can be safely instituted in adult monkeys, but that longer term and/or more severe DR is required to determine if it is capable of influencing age-sensitive indices in long-lived primates.
Accommodation, Ocular↗
Physical impairment and functional outcome in patients having lower extremity fractures after age 65.
The purpose of this study was to evaluate physical impairment and functional outcome in a group of patients who had a fracture of a lower extremity after age 65. The 30 subjects participating were treated between January 1992 and February 1998, for a unilateral fracture of the lower extremity. At the return examination, the patients' lower extremities were evaluated for range of motion (ROM) and strength. The participants also completed the Short Form 36 (SF-36) questionnaire, and their scores were compared with those of age-matched controls to determine relative disability. There were no statistically significant differences in ROM or muscle strength of the injured versus noninjured extremities, except in the case of knee flexion. The Mental Component Score (MCS) of the SF-36 in our study population was statistically different from that of controls, and there was no statistical difference in the Physical Component Score (PCS). A moderate correlation was found between the PCS and physical impairment.
Aged↗
Effects of high and low intensity aerobic conditioning programs on blood fibrinolysis and lipid profile.
The purpose of this study was to determine the effect of high and low intensity exercise conditioning programs on components pertinent to blood fibrinolysis and selected lipid profile variables in sedentary, but healthy individuals. Eighteen normal subjects were divided into two equal groups: high intensity, and low intensity exercise groups. Each subject in the high and low intensity groups exercised on a bicycle ergometer for 20 min, three times a week for 12 weeks at an intensity corresponding to 80% and 30% VO2 max, respectively. One week before and 1 week after the conditioning programs data were collected for body weight, percentage body fat, VO2 max and 12 h fasting blood levels of total tissue-type plasminogen activator (t-PA), tissue-type plasminogen activator activity (t-PAa), total plasminogen activator inhibitor (PAI-1), plasminogen activator inhibitor activity (PAI-1a), cholesterol (CHOL), triglycerides (TG), and high-density lipoprotein cholesterol (HDL-C). Post-conditioning, maximum oxygen consumption increased significantly (P < 0.05) only in the high intensity exercise group while body weight and percentage body fat did not change (P > 0.05) in either of the groups. Physical conditioning induced no statistically significant (P > 0.05) changes in the resting baseline of CHOL, TG or HDL-C. The resting baseline values of t-PA, t-PAa, PAI-1 and PAI-1a before conditioning did not vary significantly (P > 0.05) between two groups. Similarly, after training no significant change in t-PA, t-PAa or PAI-1. However, PAI-1a decreased significantly (P < 0.05) in the high intensity group, but not in the low intensity (P > 0.05). It is concluded that high, but not low, intensity physical conditioning significantly enhances the cardiorespiratory fitness and reduces the resting level of plasminogen activator inhibitor activity which may be linked with the favourable effects of exercise conditioning.
Adult↗
No impact of physical activity on the period of the circadian pacemaker in humans.
The intrinsic period tau of the circadian pacemaker in humans was investigated by means of forced desynchrony. In this protocol, during 6 scheduled days, the sleep-wake alternation was forced to a period of 20h (i.e., 13.5h for wakefulness and 6.5h for sleep). Light intensity was kept below 10 lux. Three experiments were performed. In experiment 1, 12 subjects were free to spend the available time studying, watching videos, and reading books. In experiment 2, at 2h intervals, 11 subjects spent 6 half-hour sessions per subjective day cycling with minimal effort on a cycle trainer, resulting in an average increase of heart frequency of less than 10 beats per minute. In experiment 3, 11 subjects spent the same intervals of time cycling, but now during 20 minutes per session at an average heart rate of between 140 and 150 beats per minute. Core body temperature was measured continuously. A deconvolution technique discriminated the impact of the circadian pacemaker on body temperature from the impact of activities related to sleeping and waking. From this analysis, the period of the pacemaker was derived. We found the following results: experiment 1, tau = 24.30 +/- 0.36h; experiment 2, tau = 24.17 +/- 0.45h; experiment 3, tau = 23.98 +/- 0.42h. The trend of shorter tau at higher levels of physical activity was not statistically significant. We conclude that tau in humans, determined under conditions of forced desynchrony, is very close to 24h. The suggestion from the literature that single activity pulses would predominantly yield phase delays of the circadian pacemaker is not confirmed by these multiple pulse experiments because no lengthening of tau with increasing effort was observed.
Adult↗