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Biomedical subjects

J J Koval

Publications and source records attributed to J J Koval.

51 records · Page 3Linked to original sources
PubMed1982

Design considerations in the estimation of intraclass correlation.

The design of family studies to estimate the value of an intraclass correlation coefficient p is considered when ni individuals are to be selected from each of k families, i = 1, 2, ..., k. In particular, the accuracy of a balance design (ni = n, i = 1, 2, ..., k) for estimating p is compared with the accuracy of an unbalanced "natural" design, in which the ni are sampled at random from family size distributions that tend to occur in practice. It is found for two different estimators of p that the balanced design is usually preferable, but only to a small degree if the number of families sampled is greater than 50.

Epidemiologic Methods↗
PubMed1982

The effectiveness of an electro-ionizing toothbrush in the control of dentinal hypersensitivity.

The object of the investigation was to test the value of the 3M Brand Electro-Ionizing Toothbrush in the treatment of dentinal hypersensitivity. Eighty-eight volunteers were divided into three groups, each using different methods: (I) stannous fluoride dentifrice and 3M brush without a battery; (II) stannous fluoride dentifrice and 3M brush with a 1 1/2 volt battery; and (III) strontium chloride dentifrice and 3M brush without a battery. The volunteers brushed their teeth for 3 minutes twice a day for 12 weeks using one of the three test agents. The subjects were tested at weeks 0, 2, 4, 8 and 12 by means of a cold water spray quantitated by a temperature probe. All three groups experienced improvement and by week 12 Groups II and III displayed much less sensitivity than did Group I. At the end of the 12 weeks the subjects were questioned as to benefit of treatment. The questionnaire revealed that stannous fluoride with the ionizing brush provided significantly greater relief than did the stannous fluoride alone.

Adult↗
PubMed1981

A multivariate analysis of family data.

The authors describe the application of multivariate analysis to the problem of estimating intra-family correlations and testing them for statistical significance. This is illustrated by a re-analysis of survey data collected by Miall and Oldham (Clin Sci 1958;17:459-87) on the familial aggregation of blood pressure. The multivariate analysis provides collective tests of significance for parent-child and child-child correlations based on likelihood ratio theory, and maximum likelihood estimates for individual intra-family correlations.

Blood Pressure↗
PubMed1980

The estimation of intraclass correlation in the analysis of family data.

The maximum likelihood estimator of the intraclass correlation coefficient rho in samples of unequal size from a multivariate normal distribution has been derived and compared to several other estimators, using Monte Carlo simulation. It is recommended that maximum likelihood be used if no prior knowledge concerning the value of rho is thought to be high. Fow low to moderate values of rho it is recommended that the analysis of variance estimator be used, with those families having only one member deleted from the analysis.

Analysis of Variance↗
PubMed1978

The effect of chemical fixatives on cell walls of Bacillus subtilis.

Cell walls of Bacillus subtilis were treated with several chemical fixatives which are commonly used preparatory to electron microscopy; i.e., osmium tetroxide, formaldehyde, acrolein, crotonaldehyde, and glutaraldehyde. Dimensional analysis was performed on thin sections of fixed walls from plastic embeddings and, by means of the statistical technique of multiple comparisons, significant differences were found between wall thicknesses from the various fixations. These differences varied with the fixation time and the type of fixative used in the reaction. When compared to embedded walls which had been stained before fixation, the overall effect was a reduction in wall thickness which was attributed to fixative action and not to the embedding or staining processes. The reduction of wall thickness was even more apparent when dimensions of fixed walls were compared to published dimensions of both frozen sections and freeze-etch profiles. Since these fixatives bind to reactive sites within the wall fabric, a change in electrochemical charge density is effected which can be monitored in terms of heavy-metal-binding capacity. Most monoaldehyde fixatives and osmium tetroxide render the wall as reactive, or less reactive, to uranyl acetate as unfixed walls, whereas glutaraldehyde can significantly increase the binding capacity.

Acrolein↗
PubMed1977

The relation of clinical and laboratory findings to the survival of patients with macroglobulinaemia.

The relation of clinical and laboratory findings at the time clinical presentation to subsequent survival was investigated in 204 patients with macroglobulinaemia. It was found that the ten following clinical and laboratory parameters were of prognostic significance and a further twelve were not. The best prognoses were found amongst male patients, patients aged 50-69 years and those with serum IgM paraprotein concentrations of 20-39 g/1, type lambda paraproteins, no Bence-Jones proteinuria or cryoglobulinaemia, only one paraprotein, serum cold haemagglutinin activity, serum albumin above 40 g/1 and serum urea below 10 mmol/1.

Adolescent↗
PubMedDate not supplied

Does an interaction between smoking and drinking influence the risk of Alzheimer's disease? Results from three Canadian data sets.

Investigation of the relationship of smoking and drinking to Alzheimer's disease (AD) may advance research on the cause of AD and provide a basis for treatment. Pharmacological mechanisms for an involvement of smoking and drinking are plausible but epidemiologic reports are inconsistent. Evidence of behavioural and physiological interactions suggests that tobacco and alcohol use may not only individually affect AD, but may also modify each other's effects. A modelling strategy was developed to examine the interaction between smoking and drinking on the risk of AD. Three Canadian data sets were analysed: the University of Western Ontario Dementia Study (UWODS) (n=363); the Canadian Study of Health and Aging (CSHA) (n=516), and the database from the Clinic for Alzheimer Disease and Related Disorders at the Vancouver Hospital and Health Sciences Centre, University of British Columbia site (UBC) (n=843). Multiple logistic regression models were adjusted for the potential confounders age, age squared, sex, education, family history of dementia, head injury and hypertension. Analysis of the CSHA provided evidence consistent with the hypothesis that smoking and drinking influence each other's effects on AD, with smoking reducing the risk of AD among drinkers. A similar interaction was marginally significant (p=0.052) in the UWODS data set, but not significant in the UBC data. Extension of these analyses, particularly in longitudinal studies and within genetic risk groups, is needed to determine whether this interaction can be replicated. If so, research on the biological interactions of nicotine and alcohol may provide a basis for the development of therapeutic interventions as well as providing clues to the cause of this disorder.

Aged↗
PubMedDate not supplied

The degree and type of relationship between psychosocial variables and smoking status for students in grade 8: is there a dose-response relationship?

BACKGROUND: While most research focuses on simply analyzing the differences between smokers and non-smokers, dose-response analyses may be used to find evidence of the nature of the association between psychosocial variables and involvement with smoking in adolescence. METHODS: For the study, 1,614 grade 8 students from Scarborough, Ontario, Canada, completed a self-administered questionnaire that included items on sociodemographic characteristics, experience with smoking, lifestyle, health and weight, work status, and social involvement as well as parental education, occupation, and family and peer smoking. A series of scales measuring self-esteem, stress, coping, social support, mastery, social conformity, and rebelliousness was incorporated. RESULTS: Dose-response relationships were evidenced for all categories of variables and were demonstrated for the total group and, in most cases, for males and females when analyzed separately. CONCLUSIONS: Relationships between variables are not "all or none," but may vary depending on amount or level of other factors. These relationships provide insight into the mechanisms underlying initiation to, maintenance of, and cessation of smoking and should be taken into account in programs to reduce or prevent adolescent tobacco use.

Achievement↗
PubMedDate not supplied

Are psychosocial factors related to smoking in grade-6 students?

The associations of psychosocial characteristics with both gender and smoking behavior were explored in a sample of 1552 grade-six students from 107 schools in one Ontario, Canada, school district. Ever smokers were more likely to have spending money: a part-time job; to have missed school in previous 2 months; perceive themselves to be below average or average in school; to have a mother, a father, and a sibling who smoke; to have consumed low alcohol and alcoholic beverages; and agree with fewer positive statements concerning second-hand smoke and the addictive properties of smoking. Ever smokers had more close friends who tried smoking, spent more time with friends, scored higher on depression, rebelliousness, and social conformity scales, reported more life events in the past year, and had lower scores for social support. More boys than girls had ever smoked (18.9% vs. 14.7%). Gender differences were found for sociodemographic, attitudes, social bonding, and psychosocial factors.

Adolescent↗
PubMedDate not supplied

Stress-coping and other psychosocial risk factors: a model for smoking in grade 6 students.

Smoking uptake by adolescents is best studied by a following a cohort of children as they proceed through adolescence. In this analysis of the first stage of such a study, several hypotheses about psychosocial factors that may modify the initiation of smoking in adolescents were examined in 1,552 11- and 12-year-olds in a school system in Scarborough, Canada. Investigation of the stress-coping hypothesis and other possible effect modifiers as they relate to ever-smoking revealed that stress (measured by number of life events) was important for both males and females (p = .0163 and .0056, respectively). However, the mechanisms underlying smoking appear to be different for males and females, even at this young age. In models adjusting for several factors simultaneously, rebelliousness was found to be the most important factor (p = .0001) followed by attitudes toward the effect of second-hand smoke (p = .0063) for males, whereas for females, mother smoking was the most important factor (p = .0001) followed by rebelliousness (p = .0102). Implications for design of prevention programs are discussed.

Adaptation, Psychological↗
PubMedDate not supplied

Lung function in older humans: the contribution of body composition, physical activity and smoking.

An allometric model was used to determine the important factors related to the decline in forced expiratory volume (FEV1.0) across ages 55-86 years in independently living men and women. Measurements were available from a randomized sample of 181 men and 203 women residing in London, Ontario, Canada. The effects of height, age, sex, adiposity, fat free mass (FFM), grip strength and physical activity (PA) on FEV1.0 were assessed using an allometric model to test the hypothesis that sex differences in lung function would be due in part to sex-related differences in the aforementioned variables and would therefore be eliminated by our analysis. The following model was linearized and parameters were identified using standard multiple regression: FEV1.0 = height(beta1) x FFM(beta2) x grip strength(beta3) x PA(beta4) x exp(beta0 + beta5age + beta6sex + beta7smoking + beta8%body fat) x epsilon. Results indicate that the amount of FFM and heavy intensity physical activity participated in by the elderly may be more important in influencing forced expiratory function than previously recognized. In addition, results from this study have confirmed the importance of age and height in the prediction of FEV1.0 and demonstrated a negative effect of smoking on lung function. Individuals with a greater FFM and physical activity level tended to be associated with an above average lung function performance. The cross-sectional rate of decline in FEV1.0 determined from our model was approximately 12% per decade.

Aged↗
PubMedDate not supplied

Body mass indices and skeletal size in 394 Canadians aged 55-86 years.

Demispan (finger web to midline) is the preferred index of stature in the study of the elderly where height is unreliable because of age-related loss or distortion. As a consequence, two alternative mass indices, Demiquet (male mass. demispan-2) and Mindex (female mass. demispan-1), have been proposed for use in the elderly, in place of body mass index calculated from height, which might be suspect. These gender-specific indices reflect the squared and linear relationship of height to mass in men and women respectively. To assess the independence of Demiquet and Mindex from stature and the reliability of demispan, height, demispan (second fingerweb to midline), and mass were recorded in a random sample of independent Canadian men (182) and women (212) aged 55-86 years. Both Demiquet and Mindex were highly correlated with mass, r = 0.81 (p = 0.001) and r = 0.96 (p = 0.001), respectively. In both gender groups these mass indices were independent of height and demispan. The demispan within- and between-observer errors were small -0.04(-0.16 to 0.08)cm and -0.09(-0.22 to 0.03) cm and the between-observer intraclass correlation estimate of reliability was 0.96 (lower-bound one-sided 95% CI 0.90). Demispan is a reliable and reproducible measure of stature in the elderly. Demiquet and Mindex are useful mass indices, independent of stature and suitable for use in the study of the elderly where the use of mass indices based on height may be questionable.

Aged↗
PubMedDate not supplied

An outcome measure to quantify passive stiffness of the ankle.

The primary aim of this research project was to develop a method to quantify a specific variable of neuromuscular function, passive stiffness of the ankle. It was then used to determine if values for the outcome measure varied with age and sex in a sample of elderly men and women between 55 and 85 years old. Subjects were screened for medical conditions contraindicative to testing, e.g. severe arthritis, other history of bone or muscle disorders, ankle fracture, neural disorder causing spasticity or contracture. A rotatable footplate which recorded position and resistive torque with a potentiometer and strain gauge, respectively, was linked to an electric, computer-controlled torque motor. Passive elastic stiffness, defined as the slope of the passive resistance curve at 10 degrees dorsiflexion (in N.m/degree), was greater in males, (p < .001), and increased with age (p = .002). There was a significant effect of age group on passive range of motion (ROM) values for ankle dorsiflexion (p < .001), but also a significant sex by age interaction (p = .001). Females showed a large drop from a mean of 19.3 degrees +/- 3.2 in the youngest group (55-60 yr) to 12.1 degrees +/- 5.5 in the 81 to 85 yr olds. Corresponding mean values for the middle-aged males were 15.4 degrees +/- 4.3 versus 13.1 degrees +/- 3.5 of dorsiflexion in the group of 81 to 85 yr old men. It was concluded that passive ROM of the ankle into dorsiflexion showed decreases in the elderly, which seemed to reflect less complaint tissue structures.

Aged↗
PubMedDate not supplied

Geographic differences in the attitudes, knowledge and infection control practices of Ontario dentists.

Geographic differences in the HIV related attitudes, knowledge and behaviours of 5,997 dentists in Ontario were investigated using mailed questionnaires (response rate 70%). Proportionately more respondents from larger population centres reported that they knowingly treated HIV-infected patients (p < 0.00001), they were unwilling to treat HIV-infected patients (p < 0.05), they had an exaggerated perception of the risk of HIV infection after a needlestick injury (p < 0.01), they were concerned about personal risk (p < 0.01) and staff fears (p < 0.05) related to HIV/AIDS, and that patients with HIV or AIDS should be treated in hospitals/specialized practices (p < 0.001). Multiple logistic regression analysis controlling for age, sex, and specialty, showed that respondents who practised in smaller population centres were significantly more willing to treat HIV-infected patients ( < 10,000, odds ratio = 1.6; 10,000-49,999, odds ratio = 1.3). Significantly fewer respondents in the Central West, and Central East Health Planning Region, where AIDS is most prevalent, reported that they were willing to treat HIV patients.

Adult↗