Biomedical subjects

D Couper

Publications and source records attributed to D Couper.

27 records · Page 2Linked to original sources

PubMed1997

Modelling prevalence of a condition: chronic graft-versus-host disease after bone marrow transplantation.

A variety of estimators have been proposed for modelling how the proportion of patients with a transient condition varies over time. In this paper we compare these estimators qualitatively and quantitatively and introduce a new estimator based on a generalized additive model (GAM). The assumptions on which the various estimators are based are discussed. Using simulations we compare their performances and investigate their robustness to departures from the assumptions. The GAM estimator is the only one which can incorporate covariate information. Even when estimating a single prevalence function without any covariate information the GAM estimator is seen to be preferable as long as the censoring mechanism is random censoring. The GAM prevalence estimator is applied to data on chronic graft-versus-host disease following bone marrow transplantation.

Bone Marrow Transplantation↗

PubMed1997

Factors related to infant apnoea and cyanosis: a population-based study.

OBJECTIVES: To examine the relationship between infant and parental characteristics and parental report of infant cyanosis and also hospital admission for apnoea/cyanosis. METHODS: A prospective cohort study was conducted. It involved the one-fifth of Tasmanian live births who were assessed, using a perinatal score, as being at higher risk of sudden infant death syndrome (SIDS). From 1 May 1988 to 30 April 1993, 6213 infants (89% of eligible infants) participated in the hospital (4 days postnatal age) and home interview (5 weeks postnatal age). Data on usual sleep position and infant history of cyanosis were collected at home interview. Hospital admission records for apnoea/cyanosis in the first year of life were linked to data on cohort infants in Southern Tasmania. RESULTS: Several factors were related to parental reports of cyanosis, with strong associations observed for very premature infants < 28 weeks (adjusted odds ratio [AOR] 6.06, 95% confidence interval [2.47, 14.85]), history of fits (AOR 5.59 [2.35, 13.13]); and the administration of antihistamine medication during the first month of life (AOR 3.03 [1.12, 8.18]). The median age at hospital admission was 7 weeks postnatal age. A family history of asthma, a history of fits, a history of turning blue while feeding or trouble breathing while feeding were associated with parental reports of cyanosis, breathing difficulties and also with hospital admission for apnoea/cyanosis. Other factors such as prematurity, maternal smoking, bottle feeding and a history of fever were significantly related to the infant history of cyanosis but not to hospital admission. This may partly reflect the low incidence rate (1.37%) for hospitalization for apnoea/cyanosis in the first year of life among these cohort infants. CONCLUSIONS: Several infant and parental characteristics are associated with increased risk of infant apnoea/cyanosis in this study but further population-based work with a larger group of infants hospitalised for apnoea/cyanosis should be conducted. The finding of an association between the administration of antihistamine medication and infant cyanosis highlights the possibility of adverse side-effects if antihistamine medication is administered to young infants.

Age Distribution↗

PubMed1997

Characteristics of infants receiving prompt first diphtheria-tetanus-pertussis immunisation in an infant cohort.

The Centers for Disease Control in the United States have stated that studies to determine factors associated with failure to receive the first recommended dose of diphtheria-tetanus-pertussis are required. We examined an infant cohort to identify family and infant characteristics predictive of prompt first immunisation, to document changes in prompt first immunisation rates over time and to identify reasons for immunisation delay. The study sample consisted of one-fifth of live births in Tasmania at risk of sudden infant death syndrome. From 1 January 1988 to 31 December 1994, families of 8011 infants (83 per cent of eligible infants) participated in a telephone interview when the infants were a median postnatal age of 11 weeks and 3 days. Prompt immunisation was defined as the report by parents of diphtheria-tetanus-pertussis vaccination before a postnatal age of 10 weeks. The proportion of cohort infants promptly immunised increased (P < 0.0001) over time from 1988 to 1994. Prompt immunisation was associated with various characteristics of the infant and family. The proportion of infants promptly immunised decreased as birth order increased and as the interpregnancy interval between the index child and his or her immediately elder sibling decreased. After exclusion of infants not promptly immunised because of illness, birth order and interbirth interval remained significant predictors of prompt immunisation, suggesting that these factors are acting to increase immunisation delay through pathways unrelated to their potential effect on infant illness rates.

Appointments and Schedules↗

PubMed1997

Sleeping position, infant apnea, and cyanosis: a population-based study.

OBJECTIVES: To examine the relationship between usual infant sleeping position and the parental report of infant cyanosis, pallor, breath-holding, and breathing difficulties; and to document hospital admission rates for apnea/cyanosis over time and to describe how admission rates vary by usual sleeping position. METHODS: A prospective cohort study was conducted. It involved the one fifth of Tasmanian live births that were assessed, using a perinatal score, as being at higher risk for sudden infant death syndrome (SIDS). From May 1, 1988 to April 30, 1993, 6213 infants participated in the hospital (4 days postnatal age) and home interview (5 weeks postnatal age) (89% of eligible infants). Data on usual sleep position and infant history of cyanosis were collected at home interview. Hospital admission records for apnea/cyanosis in the first year of life were linked to data on cohort infants in southern Tasmania. RESULTS: Infants who slept supine were not more likely to have been reported to experience cyanosis, pallor, or breathing problems at 1 month of age, when compared with infants sleeping in other positions. In fact, the risk of cyanosis was higher in the prone, face-down sleeping position than in the supine sleeping position (adjusted odds ratio = 4.21, 95% confidence interval [1.33, 13.28]). Among cohort infants in southern Tasmania, hospital admission rates for apnea/cyanosis did not differ by usual sleeping position or year of birth. CONCLUSIONS: Infants usually sleeping supine do not have increased rates of morbidity in relation to parental reports or hospital admissions for apnea/cyanosis. In a location where SIDS and total postneonatal mortality has fallen after intervention to reduce the prevalence of the prone position, rates of hospital admission for apnea/cyanosis have not changed.

Cohort Studies↗

PubMed1996

Is this finding relevant? Generalisation and epidemiology.

The decision about whether the findings from analytical epidemiological studies can be extrapolated to another setting is an important one. We discuss some of the issues involved in the process of generalisation. A critical systematic qualitative approach should be used. This involves an assessment of the internal validity of the study and of the nature of the study base. The study subject matter and choice of epidemiologic measure should be considered. A study base similar to the target population is essential if the study is descriptive or if there is concern about effect modifiers whose effects cannot be predicted. In addition, data from quantitative tests of study findings in different populations should be considered.

Data Interpretation, Statistical↗

PubMed1996

Features of infant exposure to tobacco smoke in a cohort study in Tasmania.

STUDY OBJECTIVES: To document changes in smoking style around infants over time and to identify factors associated with the smoking hygiene of mothers and others. DESIGN: A population based cohort study. SETTING: Population based, involving 22% of live births in Tasmania, Australia. PARTICIPANTS: From 1 May 1988 to 30 April, 1993, 6109 infants and their mothers (89% of eligible infants) participated in the hospital and home interview of the cohort study. Infants eligible for cohort entry were those assessed at birth to be at a higher risk of SIDS. MAIN RESULTS: The overall proportion of mothers who smoked during pregnancy and postnatally did not decline. Increasing trends were found for mothers and others not smoking in the same room as baby or while holding or feeding the baby, significant over the five year period. Good smoking hygiene (mother not smoking in the same room as baby) was positively associated with--first birth (OR = 1.74 (1.30, 2.33)), low birth weight (1.69 (1.27, 2.23)), being born after 1 May 1991 (1.67 (1.33, 2.11)), and private health insurance status (1.39 (1.02, 1.90)). Good smoking hygiene was negatively associated with maternal smoking during pregnancy (0.50 (0.31, 0.80)), intention to bottle feed (0.62 (0.49, 0.78)), the level of maternal postnatal smoking, increasing numbers of smokers in the household, and parents cohabiting but unmarried. A similar analysis was conducted for other household residents who smoked. CONCLUSIONS: Changes in maternal smoking prevalence have been small. The exposure of infants to tobacco smoke postnatally has decreased significantly, although a large proportion of infants are still exposed to tobacco smoke. The identification of the above parental and infant factors associated with good smoking hygiene should be useful for health education planning.

Cohort Studies↗

PubMed1996

Exercise-induced bronchial hyperresponsiveness and parental ISAAC questionnaire responses.

The predictive value of parental questionnaire responses for exercise-induced bronchoconstriction in childhood asthma has not been fully clarified. The aim of this study was to compare exercise-induced bronchial hyperresponsiveness in 7 year old children with parental responses to core questions in the International Study of Asthma and Allergies in Childhood (ISAAC) study. A cross-sectional study was conducted on 191 (91% of eligible) children from seven randomly selected schools in Southern Tasmania. Study measurements included a parental questionnaire and exercise challenge testing, using a recently validated 6 min free-running protocol. The response to exercise was assessed using forced expiratory volume in one second (FEV1) measurement. The median percentage fall in FEV1 was significantly higher in children whose parents responded positively to ISAAC questions on a history of wheeze (p = 0.0031) or asthma (p = 0.0005), recent wheeze (p = 0.0005), sleep disturbance due to wheeze (p = 0.0005), or exercise-induced wheeze (p = 0.0015). Receiver operating characteristic (ROC) curve analysis showed exercise-induced bronchial hyperresponsiveness to be a good indicator of current asthma status. Using a 12% or greater fall in FEV1 postexercise as a positive test response, the exercise challenge had sensitivity and specificity estimates for current asthma and exercise-induced wheeze of (0.58 and 0.77) and (0.60 and 0.77), respectively. In conclusion, the respiratory response to exercise was consistent with parental responses to the ISAAC questionnaire in a population-based sample of 7 year old children. These findings will assist interpretation of large ISAAC studies in terms of asthma prevalence.

Adult↗

PubMed1996

Hanging and poisoning autopsies in Fiji.

OBJECTIVE: Fiji is a Pacific nation with roughly equal numbers of indigenous Fijians and Indians. Previous studies, using police and medical records, have suggested significant racial, regional, age and gender differences in suicidal behaviour. The objective of the present study is to use a unique data set (autopsy reports) in the evaluation of earlier reports and to identify groups at greater risk. METHOD: Hanging and poisoning autopsy reports from two distinct regions were examined. RESULTS: The rate of autopsy (per 100000 population per year) among Indians (19.5) is significantly greater (p < 0.0001) than among Fijians (1.53). In the north, among the Indians, there are more autopsies in females (21.2) than males (16.8), and hanging constitutes 85% of total suicides, while in the Central and Eastern Divisions hanging constitutes only 58% of the total. These are regional influences. Among Fijians, the rates of hanging autopsy are significantly greater (p < 0.001) in males (1.98) than females (0.40); however, among Indians there is no significant difference. This is a racial difference. Hanging remains the preferred option for all groups. The mean age at autopsy is 31.7. There is no significant difference between the mean ages of the races, the sexes or the regions. There is no significant difference between the mean age of poisoning (31.5) and hanging (31.8). CONCLUSION: There is a significant racial difference in rates of suicide but the influences of region, age and method are relatively slight.

Adult↗

PubMed1995

Correlates of prone infant sleeping position by period of birth.

Intervention to avoid the prone sleeping position during infancy has occurred in various countries after evidence that it increases the risk of sudden infant death syndrome (SIDS). This study examined cohort data to determine if correlates of the prone position differed by period of birth, before intervention (1 May 1988 to 30 April 1991) compared with after intervention (1 May 1991 to 30 April 1992). The usual prone sleeping position was more closely associated with the following factors after intervention: teenage motherhood, low maternal education, paternal unemployment, unmarried motherhood, non-specialist antenatal care, not reading books to prepare for a baby, poor smoking hygiene, and bottle feeding. For example, the association of usual prone position with being unmarried shown by the odds ratio (95% confidence interval) was 0.54 (0.47 to 0.63) in the period before intervention and 1.92 (1.18 to 3.15) in the period after intervention. The alteration in correlates of the prone position reported here provide an example to support the theoretical concept that well known 'modifiable' risk factors for disease tend to be associated with each other in both populations and individuals. This phenomenon was not evident in the population before intervention, that is, before the prone sleeping position became a well known SIDS risk factor.

Adult↗