Biomedical subjects

S Chinn

Publications and source records attributed to S Chinn.

At least 145 records · Page 8Linked to original sources

PubMed1989

Longitudinal studies: design and analysis.

Objectives should determine study design, and from that the analysis should follow. Multiple objectives, some longitudinal, some cross-sectional, have implications for sampling, especially at second and subsequent occasions. The nature of the hypothesis or estimate required, and the data to be collected, will determine the frequency and timing of follow-up. Sample size must allow for follow-up failure. Difficulties with analysis result from ill-defined hypotheses, especially in relation to repeated measurements on the same outcome variable. Methods of analysis are described in relation to the hypothesis or the estimate required.

Data Collection↗

PubMed1989

Changing exposure: passive smoking.

Major effects on health postulated to result from passive smoking are increased risk of lung cancer in spouses of smokers and increased respiratory conditions in children of parents who smoke. Prospective studies have added little to knowledge of the first, but could potentially differentiate between the several causal hypotheses for the second. A number of studies have collected respiratory symptoms on lung function data on several occasions, but few have analysed them in relation to changing exposure. Only sufficient data on children whose parents change their smoking habits considerably can differentiate between effects that are immediate, reversible and non-cumulative, irreversible effects on infants only, and cumulative effects.

Adult↗

PubMed1988

Height of primary school children and parents' perceptions of food intolerance.

In the national study of health and growth parents' responses to a self completed questionnaire were used to categorize children according to their experience of food intolerance. The heights of the children in each group were then compared. Useful responses to the questions on food intolerance were received for 6813 (85%) children in the sample and measurements of height obtained for 7856 (98%). Children with food intolerance were shorter than other children. A difference in height of about 1.5 cm remained after adjusting for social and biological factors and some common symptoms in childhood using multiple regression. The number of different types of food avoided was associated with shortness in the food intolerant group but not in the non-food-intolerant group. Regardless of the underlying aetiology, these findings suggest that parents' complaints of food intolerance in their children should be taken seriously.

Body Height↗

PubMed1988

Respiratory illness and home environment of ethnic groups.

Factors contributing to differences in the prevalences of respiratory symptoms and diseases among ethnic groups were studied in primary schoolchildren living in 20 inner city areas of England in 1983. The raised prevalences of respiratory symptoms in these groups were compared with results from a national representative sample of children studied in 1982. Data on age, sex, respiratory illness, and social and environmental variables were obtained by questionnaire for 4815 children living in inner cities. The children were classified as white, Afro-Caribbean, Urdu, Gujarati, Punjabi, other Asian, or "other." Significant differences in the prevalence of respiratory conditions were found among the ethnic groups after allowance was made for the effects of interfering variables. Except for asthma all conditions were most prevalent in Afro-Caribbeans and whites. In these two ethnic groups respiratory illness was significantly associated with belonging to a one parent family and the combined use of gas cookers and paraffin heaters at home. Respiratory illness was found to vary in prevalence among ethnic groups but may be perceived differently by different groups. Further studies, measuring lung function, are necessary.

Africa↗

PubMed1988

Seasonal variation in bronchial reactivity in a community population.

Morbidity and mortality from asthma is increased during the grass-pollen season and during the autumn months in the United Kingdom. It is not apparent why this seasonal variation occurs nor whether the variation in morbidity and mortality is associated with variation in bronchial reactivity. We have measured bronchial reactivity on four occasions during 12 months in 60 subjects selected from a community population in the south of England. All subjects had had a histamine challenge test and skin tests to common antigens as part of a survey of asthma prevalence in March 1984. Further measurements of the provocative dose causing a 20% fall in FEV1 (PD20) were made at the peak of the grass-pollen season in June, at the end of September, and in the following March, and current symptoms of respiratory tract infection (RTI) were assessed on all four occasions. Geometric mean PD20 demonstrated significant seasonal variation between 1.38, 0.82, 0.92, and 1.20 mumol in March, June, September, and March, respectively (p less than 0.02). Relative to March 1984, PD20 was significantly decreased in June and September (p less than 0.005 and p less than 0.02, respectively) but not in March 1985 (p = 0.39). Within subjects atopy was significantly related to decrease in PD20 in September (p less than 0.05) and in March 1985 (p less than 0.025) but not in June (p = 0.40). Change in PD20 between occasions was unrelated to RTI symptoms, age, or smoking status, but it was related to change in baseline FEV1/FVC (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1988

Class-specific herpes simplex virus antibodies in sera and cervical secretions from patients with cervical neoplasia: a multi-group comparison.

Serum and cervical secretions were collected from patients with cervical dysplasia, carcinoma-in-situ (CIS), squamous cell carcinoma (cervical SCC), and controls with normal cervices, attending clinics within the West Lambeth Health District, London. Enzyme-linked immunosorbent assays were used to examine cervical secretory IgA (sIgA) and serum IgG and IgA antibodies to herpes simplex virus (HSV). Sexual and demographic factors were considered during data analysis, which involved fitting multiple linear or multiple logistic regressions to HSV antibody levels. Prevalence of sIgA-HSV and levels of serum antibodies to HSV in all groups were compared with those of gynaecology controls. Caucasian women with mild dysplasia had a significantly higher prevalence of sIgA-HSV. Serum IgG levels to HSV (IgG-HSV) were significantly elevated in women with mild dysplasia and severe dysplasia/CIS. Serum IgA levels to HSV1 (IgG-HSV1) were significantly higher in women with cervical SCC (after adjusting for smoking habits) and other genital tumours. Significantly higher levels of serum IgA to HSV2 (IgA-HSV2) were also found among Caucasian women with cervical SCC. The possible role of HSV as a co-factor in cervical carcinogenesis is discussed.

Antibodies, Viral↗

PubMed1988

Passive smoking and respiratory conditions in primary school children.

The effect of passive smoking on respiratory symptoms of children aged 5 to 11 years was investigated in over 4000 English children and nearly 800 Scottish children participating in the National Study of Health and Growth in 1982. After adjusting for associations of respiratory symptoms with age, sex, and a number of potentially confounding variables, significant associations were found of wheeze, both occasional and persistent, day or night cough, and bronchitis attacks with number of cigarettes smoked by parents at home for English children and for occasional wheeze in Scottish children. Asthma attacks and cough first thing in the morning showed positive but not statistically significant associations in English children. The presence of at least one condition was statistically significant in both English and Scottish children. The largest relative risk for exposure to 20 cigarettes a day compared to no exposure was 1.60 for persistent wheeze in English children (95% confidence interval 1.17-2.18).

Child↗

PubMed1988

Comparison of histamine and methacholine for use in bronchial challenge tests in community studies.

Measurement of bronchial reactivity is widely used in epidemiological surveys. Histamine has been compared with methacholine inhalation challenge in two samples of adults from a small town to determine which is the better agent for use in community studies. Increasing doses of histamine and methacholine were given, up to a maximum of 4 and 12 mumol respectively, according to the method of Yan et al, the provocative dose of agonist causing a 20% fall in FEV1 (PD20) being measured. More subjects had a measurable PD20 with methacholine than with histamine, both in a random sample of 108 subjects (25 v 11 subjects, p less than 0.01) and in an additional 95 subjects selected because of wheeze in the last 12 months (67 v 48 subjects, p less than 0.01). Side effects were mild with both agents but histamine caused voice change in more subjects (21% v 11%). Repeatability was assessed in a further group of subjects with wheeze in the last year. The 95% range for a single estimation of PD20 in subjects with a measured PD20 on at least one occasion was +/- 2.5 doubling doses for histamine (n = 25) and +/- 2.1 doubling doses for methacholine (n = 33). Thus methacholine has advantages over histamine for community studies of bronchial reactivity as it is possible to use doses that produce more PD20 measurements with fewer side effects.

Adolescent↗

PubMed1988

The relation between change in airway reactivity and change in respiratory symptoms and medication in a community study.

Airway reactivity is known to increase in relation to the severity of asthma, and, in the community, hyperreactivity has been shown to be associated with respiratory symptoms such as wheezing and shortness of breath. However, the relation between change in airway reactivity and change in the severity of respiratory symptoms and change in the use of asthma medications within subjects has not been studied. We have investigated this relationship in a community population. In September 1984 and March 1985, the provocative dose of histamine producing a 20% fall in FEV1 (PD20) was measured, and respiratory symptoms and medication use assessed by questionnaire in 78 subjects taking part in a study of seasonal changes in airway reactivity. On both occasions, PD20 was negatively correlated with current frequency of wheezing, with the amount of asthma medication in regular use, and with the current general assessment of breathing problems. In the 45 subjects who had a PD20 value of 8 mumol or less on at least one of the two occasions tested, PD20 increased between September and March by 0.46 (SEM, 0.32) doubling doses of histamine (p = 0.16). Within subjects, change in PD20 was negatively correlated with change in the frequency of wheezing in the past month (p less than 0.005) and with change in medication use (p less than 0.05). This study demonstrates that PD20 is related to the severity of respiratory symptoms and medication use, and that change in airway reactivity within subjects in a community population is associated with changes in the frequency of wheezing and in the use of asthma medication.

Adult↗

PubMed1987

Analysis of human lymphocyte transformation responses to graded doses of T cell mitogens by curve fitting.

The between-group comparison of complete lymphocyte transformation dose-response curves is complex. We have therefore derived a mathematical model of the dose-response characteristics of human mononuclear cells to stimulation by concanavalin A (ConA) and purified phytohaemagglutinin (PHA), in order to simplify such analyses. This model describes dose-response curves in terms of the magnitude of the peak response, the dose of mitogen that elicits the peak and an estimate of the range of mitogen doses which induce a response. Responses to ConA were described by the model more precisely than those to PHA. Furthermore, use of the model revealed differences between anorexia nervosa patients and healthy subjects in terms of the dose of mitogen necessary to elicit a peak response and the range of mitogen concentrations producing a response. It is proposed that this form of mathematical treatment may be of use for the comparison of lymphocyte transformation dose-response curves and for the valid rejection of suspect results.

Anorexia Nervosa↗

PubMed1987

Parents' perceptions of food intolerance in primary school children.

In a study of about 7000 children, parents' perceptions were used to examine the prevalence of food intolerance, the types of food implicated, the association of intolerance with diseases, and the social background of those identified as being food intolerant. One hundred and ninety two children (3%) were perceived as being food intolerant, with a further 105 (2%) being classed as intolerant under a less stringent definition of intolerance. For 128 (67%) of these children a doctor was consulted. The pattern of food avoided was very similar in children for whom the decision to exclude certain foods was made by health staff and in those for whom the parents themselves made decisions about their child's diet. A strong association was seen between the mother's level of education and the child being perceived as being food intolerant. Between 20% and 30% of children with a disease associated with food intolerance--for example, eczema--had currently or previously avoided some types of food. The results of this study emphasise the need to develop criteria to tackle the growing demand for National Health Service treatment by parents who believe their child to be food intolerant.

Child↗

PubMed1987

On measuring repeatability of data from self-administered questionnaires.

It is usually necessary to estimate repeatability of a self-administered questionnaire from responses by subjects on just two occasions. It is shown that it is not possible to estimate false positive and false negative classification rates separately, but that an average correct classification can be calculated. This is recommended as the appropriate absolute measure of repeatability, whereas the kappa statistic, which can be interpreted as the ratio of between subject to total variation, is a measure of repeatability relative to prevalence of responses. Both measures should be calculated to give complete information on repeatability, analogous to absolute and relative measures used for continuous variables.

False Negative Reactions↗

PubMed1987

Vegetarianism and growth in Urdu, Gujarati, and Punjabi children in Britain.

As part of a nutritional surveillance system of primary school children the relation between growth and vegetarianism in the Urdu, Gujarati, and Punjabi groups was explored. The aim of the analysis was to ascertain if vegetarian children from ethnic minorities are at a disadvantage in terms of nutritional status within their group of origin. Data for 80.7% of 473 Urdu children, 86.6% of 551 Gujarati children, and 84.4% of 1265 Punjabi children were available for the analysis. No significant differences in weight-for-height and triceps skinfold were found between vegetarians and non-vegetarians even after adjustment for potential confounding variables. Vegetarian girls tended to be shorter than non-vegetarian girls in all Asian groups, although this difference reached a statistically significant level (p less than 0.01) only in the Urdu group. Although our findings should be interpreted with caution they indicate that health visitors and other health staff should be aware of the possible contribution of vegetarianism to the nutritional status of Asian girls.

Child↗

PubMed1987

Descriptive epidemiology of bronchial reactivity in an adult population: results from a community study.

The bronchial response to inhaled histamine has been suggested as an epidemiological tool for assessing the prevalence of asthma, though the exact relationship between reactivity and asthma is unknown. Tests of bronchial reactivity to histamine were carried out in 511 subjects aged 18-64 years, randomly selected from the population in two areas of the South of England, who had returned questionnaires on respiratory symptoms. Bronchial reactivity to less than or equal to 8 mumol histamine was present in 14% and was associated with positive skin test responses to common allergens and with smoking history. Both of these relationships were in turn dependent on age, skin sensitivity being the more important determinant of reactivity in the young and smoking the more important in older subjects. Bronchial reactivity was least prevalent in the 35-44 year age group. No independent effect on reactivity of sex, social class, or area of residence was detected, and no significant effect from recent respiratory tract infections. Interpretation of the bronchial response to histamine in selected groups of subjects must take account of age, atopic state, and smoking history.

Adult↗

PubMed1987

Estimation and repeatability of the response to inhaled histamine in a community survey.

Epidemiological problems arising from the absence of an agreed definition of asthma have led to the use of bronchial reactivity tests in community surveys of asthma prevalence. Since only a minority of the general population will develop bronchoconstriction in response to the dose of histamine considered acceptable for use in the community it is important to make maximum use of the data available. Several methods for summarising the information in the dose-response curve obtained from a histamine challenge test have been compared. A standardised histamine challenge test was administered to 797 subjects selected from two communities, and a repeat test to 106 subjects. The test was well accepted. For most subjects FEV1 rose initially after administration of histamine (median rise 100 ml), so maximum FEV1 was used as the baseline from which the 20% fall to achieve a PD20 was calculated. In order to use all the data rather than just two points on the FEV1-log dose graph, PD20 was estimated by means of curve fitting, and the values were compared with PD20 from linear interpolation. An exponential curve was found to fit the data well. Extrapolation from the maximum dose of 4 mumol up to 8 mumol was allowed in the estimation of PD20 by both methods. The curve fitting method gave slightly more reproducible PD20 values than did linear interpolation, and also gave more estimates in the range 0.03-8 mumol. The repeatability of PD20 compared well with that of asthmatic subjects tested in a clinical environment. Curve fitting has an advantage over linear interpolation in large community studies, for which analysis of data by computer is essential.

Adolescent↗

PubMed1987

National Study of Health and Growth: effect of change in design with reference to efficiency of mixed longitudinal studies for measuring trends.

The National Study of Health and Growth (NSHG) is a surveillance system which monitors the growth of primary school children in England and Scotland, set up in 1972 following changes in the school milk and welfare system. However, the study contained few children from inner city areas or ethnic minorities. In 1982 its design was changed from one in which the same areas were surveyed every year, to two separate systems with areas surveyed every two years, one set of areas corresponding to those in the original study, and the other set consisting of inner city and ethnic minority areas. The precision of the estimates of trends in height and weight for each system was smaller than that of the original system, but by less than 50%, so that an overall gain in information was achieved. Studies of mixed longitudinal design are shown also to be generally, but not always, less efficient for estimating trends than independent cross-sectional surveys obtaining the same number of measurements.

Body Height↗

PubMed1987

Developing a new questionnaire for measuring the prevalence and distribution of asthma.

Over the last few years the International Union Against Tuberculosis (IUAT) has been developing a new questionnaire for measuring the prevalence and distribution of asthma. The methods that are being used to establish the validity of the questionnaire are described, along with some preliminary results. These results are used to illustrate a number of problems. Current work concerning the further development and testing of the questionnaire is described.

Asthma↗

PubMed1987

A randomized controlled trial of an information booklet for hypertensive patients in general practice.

A randomized controlled trial of an information and medical record booklet designed to improve patient understanding and participation in the management of hypertension was conducted in six inner London general practices. After one year there were no significant differences between the group who had received the booklets and the control group in mean systolic or diastolic blood pressure, but the study group scored significantly higher on knowledge about hypertension and its management. However, the difference between the two groups was small, possibly because both groups started with a high level of understanding about hypertension and its management. In addition, the mean diastolic blood pressure in the control group showed that the treatment provided was already satisfactory, and that there was little need for improvement. Nevertheless, the information booklet evaluated in this study provides health professionals with a highly acceptable method of informing the patient about hypertension and its management and could be used both in hospital and general practice.

Adult↗