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Biomedical subjects

S Chinn

Publications and source records attributed to S Chinn.

At least 19 recordsLinked to original sources
PubMed1995

Adjustment of reported prevalence of respiratory symptoms for non-response in a multi-centre health survey.

BACKGROUND: Estimation of non-response bias by modelling prevalence as a function of the number of mailings required to achieve a response, or of the cumulative response, has been advocated, but the models have not incorporated age and sex, differential response rates by age and sex, or season of response. METHODS: The effect on age-sex standardized prevalence of estimating non-response bias using a variety of models was investigated using data on nine symptom and medication questions from 13,007 subjects in the three English centres of the European Community Respiratory Health Survey. Comparison was made of goodness of fit and the prediction of responses in a 25% follow-up sample with the observed values. RESULTS: Despite low response rates in Cambridge and significant decreases in prevalence with additional mailings or increasing cumulative response in Norwich, there were only small effects on estimated age-sex standardized prevalences. No model was consistently better for any centre or question. CONCLUSIONS: The models are useful for exploring the sensitivity of estimated prevalence to non-response bias, but should be used with caution to adjust estimates. Ideally first mailings should be staggered over the whole year so that mailing and season are not confounded, and sufficient mailings or other contacts carried out for the whole sample to ensure a high response rate.

Adult↗
PubMed1995

Monitoring the growth of children: conclusions from a long-term study.

BACKGROUND: The National Study of Health and Growth (NSHG) was set up in 1972 to monitor the growth of primary school children. Areas were selected in England and Scotland by stratified random sampling. Schools within these areas were visited annually until 1982, biennially thereafter, resulting in a mixed longitudinal design. The reasons for the original design and the study as it has operated are reviewed, with advantages and disadvantages compared to the monitoring system now to be implemented by the Department of Health. METHODS: Description of the statistical and interpretive problems of monitoring rates of growth and a comparison of the response rates achieved in the two types of monitoring. RESULTS: Although the design of the NSHG was selected in order to monitor rates of growth this presents statistical problems. The usable information is contained in trends in attained height rather than in rates of growth. This study has achieved an average response rate of over 95%; less than 78% can be expected from the proposed survey of households. CONCLUSIONS: The small loss of efficiency of the mixed longitudinal design compared with repeated cross-sectional studies is more than compensated for by its high response rate and the comparability of data over time, neither of which can be guaranteed by the proposed survey.

Body Height↗
PubMed1995

Interpretation of measured red cell mass and plasma volume in adults: Expert Panel on Radionuclides of the International Council for Standardization in Haematology.

Four European centres provided height and weight data on 202 males and 204 females undergoing red cell mass (RCM) and plasma volume (PV) measurements. For these populations, the RCM and PV predictions by the various published methods were compared. It was shown clearly that predictions based solely on body weight were inappropriate, particularly because approximately half of the male and female populations could be regarded as overweight or obese. Although there was reasonable agreement in the prediction values given by the formulae based on both height and weight, it was not possible to establish which formulae could be recommended. For that reason, the published literature containing normal RCM and PV measurements were re-examined. RCM data for 283 males and 171 females and PV data for 100 males and 67 females were included. Measurements were standardized for variables such as trapped plasma in the PCV, exclusion of buffy coat in the PCV and calculation of PV at zero time. As a result of this analysis, prediction formulae based on surface area for RCM and PV with 98/99% reference ranges have been established.

Adult↗
PubMed1995

Cross sectional stature and weight reference curves for the UK, 1990.

The current reference curves of stature and weight for the UK were first published in 1966 and have been used ever since despite increasing concern that they may not adequately describe the growth of present day British children. Using current data from seven sources new reference curves have been estimated from birth to 20 years for children in 1990. The great majority of the data are nationally representative. The analysis used Cole's LMS method and has produced efficient estimates of the conventional centiles and gives a good fit to the data. These curves differ from the currently used curves at key ages for both stature and weight. In view of the concerns expressed about the current curves and the differences between them and the new curves, it is proposed that the curves presented here should be adopted as the new UK reference curves.

Adolescent↗
PubMed1995

Physical fitness of 9 year olds in England: related factors.

STUDY OBJECTIVE: To examine the influence of social factors, passive smoking, and other parental health related factors, as well as anthropometric and other measurements on children's cardiorespiratory fitness. DESIGN: This was a cross sectional study. SETTING: The analysis was based on 22 health areas in England. PARTICIPANTS: The subjects were 299 boys and 282 girls aged 8 to 9 years. Parents did not give positive consent for 15% of the eligible sample. A further 25% of the eligible sample did not participate because the cycle-ergometer broke down, study time was insufficient, or they were excluded from the analysis because they were from ethnic minority groups or had missing data on one continuous variable. MEASUREMENTS AND MAIN RESULTS: Cardiorespiratory fitness was determined using the cycle-ergometer test. It was measured in terms of PWC85%-that is, power output per body weight (watt/kg) assessed at 85% of maximum heart rate. The association between children's fitness and biological and social factors was analysed in two stages. Firstly, multiple logistic analysis was used to examine the factors associated with the children's ability to complete the test for at least four minutes. Secondly, multiple linear regression analysis was used to examine the independent association of the factors with PWC85%. In the logistic analysis, shorter children, children with higher blood pressure, and boys with a larger sibship size had poorer fitness. In the multiple regression analysis, only height (p < 0.001) was positively associated, and the sum of skinfold thicknesses at four sites (p = 0.001) was negatively associated with fitness in both sexes. In girls, a positive association was found with pre-exercise peak expiratory flow rate (p < 0.05), and there were negative associations with systolic blood pressure (p < 0.05) and family history of heart attack (p < 0.05). In boys an association was found with skinfold distribution and fitness (p < 0.05), so that children with relatively less body fat were fitter. Social and health behaviour factors such as father's social class, father's employment status, or parents' smoking habits were unrelated to child's fitness. CONCLUSION: Height and obesity are strongly associated, and systolic blood pressure to a small extent, with children's fitness, but social factors are unrelated.

Blood Pressure↗
PubMed1995

Factors associated with weight for height and skinfold thickness in British children.

STUDY OBJECTIVE: To examine the associations of social and biological factors with measures of obesity in children. DESIGN: The study had a cross sectional design. SETTING: The analyses were based on data from two national study of health and growth cross sectional surveys. The "representative sample" comprised 1990 data from 22 English areas and 1990-91 data from 14 Scottish areas; the "inner city sample" comprised 1991 data from 20 English areas. PARTICIPANTS: The subjects were primary school children aged mainly 5-11 years living in England and Scotland. The "representative" sample included 10,628 children--6463 living in England and 4165 living in Scotland. The "inner city" sample included 7049 children--2183 white, 1124 Afro-Caribbean, 2696 Indian subcontinent, and 1046 from other groups. Due to missing values on continuous variables, 8374 children were included in the analyses. MEASUREMENTS AND MAIN RESULTS: The relation between social environment and childhood overweight was studied using several indicators of obesity. Triceps, subscapular, the sum of triceps and subscapular skinfolds, and weight for height were used as dependent variables. The analyses were carried out in two stages. Firstly, multiple linear regression analyses were used to assess the factors associated with dependent variables treated as continuous. Secondly, multiple linear logistic regression analyses were used to examine the association between independent factors and overweight and fatness defined as binary variables. Birth weight, mother's body mass index (BMI), and father's BMI were consistently associated (p < 0.001) in all models and were the variables that contributed most to the explained variation in the dependent variables. In the multiple regression analyses there was a consistent interaction between the effects of ethnic origin and family size on each outcome variable. In the logistic regression analyses the interaction was not significant, and highly significant associations between both overweight and fatness with the number of children were shown. Ethnic group was not significantly associated with overweight but it was with fatness. The strengths of the remaining significant associations were slight and inconsistent in relation to the dependent variables or the type of analysis. CONCLUSION: Very few variables were associated with measures of overweight and fatness. The only useful factor that was highly associated with all measures of fatness was the parents' BMI. Strategies to prevent childhood obesity should be aimed at the total population and special emphasis should be placed on families in which one or both parents are overweight.

Birth Weight↗
PubMed1994

Trends in weight-for-height and triceps skinfold thickness for English and Scottish children, 1972-1982 and 1982-1990.

Data from the 1972, 1982 and 1990 surveys of the National Study of Health and Growth were used to calculate changes in height, weight, triceps skinfold thickness and weight-for-height index for children aged between 4.5 and 11.99 years. There were data for 7887, 6396 and 6420 white English children in the 3 years respectively, and data for 1586, 1191 and 1317 Scottish children. Increases in all measurements were found from 1972 to 1990, except for weight-for-height in English boys, and were generally greater from 1982 to 1990 than from 1972 to 1982. Approximately a third of the increases in weight-for-height and triceps skinfold thickness from 1972 to 1990 were associated with increases in parental body mass indices and decreases in family size. No consistent differences in trends were found between social groups. Greater trends were found for girls and for Scottish children, and Scottish boys are now heavier and fatter than their English counterparts. Trends in weight-for-height and fatness may have implications for future trends in coronary heart disease, and lessen the likelihood that the targets for reductions in obesity in the White Paper Health of the Nation will be met. Preventive measures should be directed at the entire population.

Body Height↗
PubMed1994

Response to venepuncture for monitoring in primary schools.

The feasibility and acceptability of collecting blood from children by venepuncture was assessed in a sample of 593 children from seven primary schools in Canterbury. Venepuncture is necessary to obtain blood for the measurement of haemoglobin, ferritin, and cholesterol in line with Department of Health surveys in England. Return of consent forms was 87%; 75% of parents in the total sample allowed their child to be tested. Response rates differed between schools. Only 4% of eligible children refused to participate at the time of testing. In 22 (3.7%) children a blood sample could not be obtained or the volume was insufficient for analysis. There was a significant difference in the failure rate between phlebotomists. Venepuncture in the school setting was technically feasible and acceptable. The reluctance of some groups in the community to participate may bias the sample.

Bloodletting↗
PubMed1994

Serum total cholesterol and ferritin and blood haemoglobin concentrations in primary schoolchildren.

Serum total cholesterol and ferritin and haemoglobin concentrations were measured in blood samples obtained by venepuncture in 378 of 593 children aged 5-6 or 8-9 years from seven primary schools in Canterbury. This study formed part of an investigation to assess the feasibility of including a venepuncture procedure for monitoring purposes in primary schoolchildren. Although only one child had a very low haemoglobin concentration of 61 g/l, a large percentage, 25% in the rising 6 years and 7% in the rising 9 years, had concentrations between 100 and 115 g/l--that is, less than the reference fifth centile. Eight per cent had a serum ferritin concentration less than 8 micrograms/l. Cholesterol concentrations higher than 5.2 mmol/l were found in 20% of the 5-6 year olds and 23% of the 8-9 year olds, and in 19% of boys and 25% of girls. About 5% of children had cholesterol concentrations above 6 mmol/l. The number of children with anaemia, iron deficiency, and high cholesterol raises serious concerns about the nutritional and coronary heart disease risk of British children.

Age Factors↗
PubMed1994

The European Community Respiratory Health Survey.

The European Community Respiratory Health Survey (ECRHS) was planned to answer specific questions about the distribution of asthma and health care given for asthma in the European Community. Specifically, the survey is designed to estimate variations in the prevalence of asthma, asthma-like symptoms and airway responsiveness; to estimate variations in exposures to known or suspected risk factors for asthma, and assess to what extent these variations explain the variations in the prevalence of disease; and to estimate differences in the use of medication for asthma. The protocol provides specific instructions on the sampling strategy adopted by the survey teams, as well as providing instructions on the use of questionnaires, the tests for allergy, lung function measurements, tests of airway responsiveness, and blood and urine collection. The principal data collection sheets and questionnaires are provided in the appendices, together with information on coding and quality control. The protocol is published as a reference for those who wish to know more of the methods used in the study, and also to give other groups who wish to collect comparable data access to the detailed methodology.

Asthma↗
PubMed1994

Prevalence of asthma and asthma-like symptoms in young adults living in three east Anglian towns.

BACKGROUND: The European Community respiratory health survey is examining the prevalence of asthma and risk factors for asthma. AIM: As part of this multinational survey, a study was undertaken to determine the prevalence of asthma and asthma-like symptoms in young adults living in Cambridge, Ipswich and Norwich using a postal questionnaire. METHOD: A previously validated symptom questionnaire was sent to 2500 men and 2500 women aged 20-44 years living in and registered with a general practitioner in each of the three towns. RESULTS: In total, approximately 9000 adults responded. The prevalence of symptoms suggestive of asthma was found to be similar in the three towns. Of respondents, 8% reported having been woken by an attack of shortness of breath at some time in the last 12 months, higher than previously reported. Five per cent reported having had an asthma attack. CONCLUSION: General practitioners wishing to examine asthma prevalence in their own practice population could use a similar methodology.

Adult↗
PubMed1992

Interregional variations in measures of health from the Health and Lifestyle Survey and their relation with indicators of health care need in England.

STUDY OBJECTIVE: The aim was to assess the extent to which a range of routinely available need indicators which have been suggested for use in NHS spatial resource allocation formulas were associated geographically in England with the different dimensions of population health status collected in the 1985/86 Health and Lifestyle Survey (HLS). DESIGN: Regional health authorities were ranked according to each of the HLS health variables which varied significantly between authorities. The HLS health variables were regressed on a selection from the range of routinely available morbidity and socioeconomic indicators available from the 1981 census. The potential need indicators were also regressed on the health variables. SETTING: The analyses were undertaken at individual level and at regional health authority level in England. SUBJECTS: The study comprised the English component of the HLS random sample representative of the population in private households in Great Britain. MAIN RESULTS: The different HLS health variables did not yield consistent regional health authority rankings. Among the variables, forced expiratory volume in one second (FEV1) and self assessed health appeared to be associated with most of the other health and need variables except longstanding illness. Longstanding illness was not strongly associated with any of the other HLS health variables but appeared to show some association with three deprivation indices constructed from the 1981 Census. CONCLUSIONS: There may be a case for including a measure of chronic ill health in the new NHS system of capitated finance in addition to the all cause standardised mortality ratio which is used currently as a measure of need for health care.

Chronic Disease↗
PubMed1992

Trends in body mass index in young adults in England and Scotland from 1973 to 1988.

STUDY OBJECTIVE: The aim was to determine whether the mean body mass index of young adults in England and Scotland had increased during the years 1973 to 1988. DESIGN: The study was an analysis of reported heights and weights for parents of children participating in a mixed longitudinal study of children's growth. SETTING: 20 study areas (16 in England and four in Scotland) were selected by stratified random sampling. SUBJECTS: Subjects were parents of 5229 children who were new entrants to the study in the years 1973-6 and 1982-8. After excluding cases containing missing values on continuous variables, data for 4568 (87%) women (mean age 30 years) and 4029 (77%) men (mean age approximately 32 years) were analyzed. MEASUREMENTS AND MAIN RESULTS: Changes in weight for height over time were determined using body mass index as dependent variable, adjusting for age, social class, family size, and study area. In women, mean body mass index showed an annual increase of 0.10 (95% CI 0.03 to 0.17%) per year of study. Body mass index also increased with increasing age and family size and was greatest for women with husbands in manual occupations. The secular trend in body mass index in women was not explained by changes in the distribution of these variables. The proportion of women with BMI greater than 25 kg/m2 increased over the study period. In men the secular trend in body mass index was not quite significant in this age group [annual increase 0.05% (-0.01 to 0.12%)]. CONCLUSIONS: There has been an increase in the body mass index of young women in England and Scotland over the years 1973 to 1988. This increase was not explained by changes in the age, parity, social class of the subjects sampled. Evidence of a trend in men was not found.

Age Factors↗
PubMed1992

Portable liquid oxygen and exercise ability in severe respiratory disability.

BACKGROUND: The development of portable liquid oxygen systems, capable of delivering high flow rate oxygen for long periods, justifies reassessment of the value of supplemental oxygen to aid exercise tolerance in patients with chronic respiratory insufficiency. The type of exercise test and the low oxygen flow rates previously used may account for the variable and often poor responses to supplemental oxygen reported in earlier studies. METHODS: The walking tolerance of 30 patients with severe respiratory disability was measured while they were breathing air and increasing doses of supplemental oxygen (2, 4, 6 1/min) by using both the standard six minute walking test and an endurance walking test. To assess the initial learning effect and repeatability of the walking tests, three six minute walks and three endurance walks were performed on day 1 and a single walk of each type on days 2, 3, and 14. In addition, oxygen dosing studies were performed on days 2 and 3 after the initial baseline walking tests. Each dosing study comprised four endurance walking tests or four six minute walking tests with patients breathing either air at a flow rate of 4 1/min from a portable cylinder or supplemental oxygen at a flow rate of 2, 4 or 6 1/min from a portable liquid oxygen supply. The order of the tests was randomised. Walking distance with each flow rate of oxygen was compared with walking distance with patients carrying cylinder air and for the initial unburdened walks. Breathlessness was assessed by visual analogue scoring on completion of each walk. RESULTS: Exercise ability and breathlessness were significantly improved with supplemental oxygen and this benefit outweighed the reduction in performance resulting from carrying the portable device. Supplemental oxygen at flow rates of 2, 4, and 6 1/min increased mean endurance walking distances by 37.9%, 67.7% and 85.0% and six minute walking distances by 19.2%, 34.5%, and 36.3% by comparison with distances when the patient was carrying air with a flow rate of 4 1/min. The additional work of carrying the portable gas supply reduced endurance walking distance by 22.2% and six minute walking distance by 14.1% by comparison with a baseline unburdened walk. Comparison of supplemental oxygen at 2, 4, and 6 1/min with the baseline unburdened performance showed increased endurance walking distances of 7.3%, 30.4%, and 43.9% and six minute walking distances of 2.3%, 15.5%, and 17.0%. Walking distance was increased by more than 50% by comparison with an unburdened walk in seven patients with the endurance walking test but in only three patients with the six minute walking test. The benefit was similar in patients with obstructive and with interstitial lung disease. Individual responses were variable and only desaturation during the baseline walk in patients with obstructive lung disease had any predictive value for benefit with oxygen. CONCLUSION: As there was no clear relation between response to oxygen therapy and the patients' characteristics, assessment for supplemental oxygen therapy will depend on exercise testing. It is suggested that portable oxygen should be considered only if a patient shows a 50% improvement in exercise ability with high flow rate oxygen (4-6 1/min) by comparison with an unburdened walk.

Ambulatory Care↗
PubMed1992

Height and age adjustment for cross sectional studies of lung function in children aged 6-11 years.

BACKGROUND: No standard exists for the adjustment of lung function for height and age in children. Multiple regression should not be used on untransformed data because, for example, forced expiratory volume (FEV1), though normally distributed for height, age, and sex, has increasing standard deviation. A solution to the conflict is proposed. METHODS: Spirometry on representative samples of children aged 6.5 to 11.99 years in primary schools in England. After exclusion of children who did not provide two repeatable blows 910 white English boys and 722 girls had data on FEV1 and height. Means and standard deviations of FEV1 divided by height were plotted to determine whether logarithmic transformation of FEV1 was appropriate. Multiple regression was used to give predicted FEV1 for height and age on the transformed scale; back transformation gave predicted values in litres. Other lung function measures were analysed, and data on inner city children, children from ethnic minority groups, and Scottish children were described. RESULTS: After logarithmic (ln) transformation of FEV1 standard deviation was constant. The ratios of actual and predicted values of FEV1 were normally distributed in boys and girls. From the means and standard deviations of these distributions, and the predicted values, centiles and standard deviation scores can be calculated. CONCLUSION: The method described is valid because the assumption of stable variance for multiple regression was satisfied on the log scale and the variation of ratios of actual to predicted values on the original scale was well described by a normal distribution. The adoption of the method will lead to uniformity and greater ease of comparison of research findings.

Age Factors↗
PubMed1992

Comparison of bronchial reactivity and peak expiratory flow variability measurements for epidemiologic studies.

Inclusion of a standardized measurement of airway function is important in epidemiologic studies of asthma to facilitate comparison between different studies. Bronchial reactivity is widely used in such studies, but measurement of peak expiratory flow (PEF) variability has a number of potential advantages. We compared PEF variability with methacholine challenge tests in a community population sample. Subjects selected at random (n = 95) and on the basis of having experienced wheeze in the last 12 months (n = 130) performed a challenge test with methacholine to a maximum dose of 12.25 mumol and made serial PEF recordings every 2 h for a week. PEF variability was expressed as mean daily maximum amplitude as a percentage of the mean (amplitude % mean). Increased bronchial reactivity and PEF variability were arbitrarily defined as values above the 10th or below the 90th percentiles in the random sample. A measurement of amplitude % mean was available from all 225 subjects, whereas only 115 (51%) had a measurable PD20 methacholine. PD20 measurements correlated weakly but significantly with amplitude % mean (r = -0.44, p less than 0.001). Increased values of both bronchial reactivity and PEF variability were related to the presence of respiratory symptoms in the week before testing. Asthma was more strongly related to increased bronchial reactivity than to PEF variability. Both measurements showed a strong association with atopy and the intraclass correlation coefficients (ratio of between-subject to total variance) were similar for both.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Weight-for-height in children aged 4-12 years. A new index compared to the normalized body mass index.

Data from the 1990 survey of the National Study of Health and Growth, comprising 3357 white English boys and 3050 white English girls, were used to construct and evaluate a new index of weight-for-height. Prediction of triceps + subscapular skinfold thickness, using half of the data, led to the index (weight -9)/height3.7, where weight was in kilograms, height in metres. Using the second half of the data the index was shown to have almost as good a correlation with normalized (triceps + subscapular skinfold) as the body mass index (BMI) in children aged 4-12 years. The new weight-for-height index had stable variance from age 4 to 12 years after simple log transformation, unlike the BMI which required transformation via three age-related parameters prior to analysis or centile calculation. Neither index was a good proxy for skinfold measurements for comparison of ethnic groups. From data from inner city areas surveyed in 1989 children of Indian subcontinent origin had substantially lower weight-for-height, but only Gujarati children were thinner than white children, whereas Afro-Caribbean children were slightly heavier for their height, but thinner. Centiles of weight-for-height, and of BMI by age, for ages 4-12 years, were calculated for white English boys and white English girls.

Body Height↗