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Biomedical subjects

A L Ponsonby

Publications and source records attributed to A L Ponsonby.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1995

The contribution of changes in the prevalence of prone sleeping position to the decline in sudden infant death syndrome in Tasmania.

OBJECTIVE: To determine the independent contribution of changes in infant sleep position to the recent decline in sudden infant death syndrome (SIDS) rate in Tasmania. DESIGN: (1) A comparison of the whole population incidence of SIDS before and after an intervention to reduce the prevalence of prone sleeping position. (2) A within-cohort analysis of the contribution of sleep position and other exposures to the decline in SIDS after the intervention. SETTING: Tasmania, Australia. PARTICIPANTS: (1) All SIDS cases from 1975 through 1992. (2) A sample of one in five infants born in Tasmania who at perinatal assessment were scored to be at higher risk for SIDS since January 1988. Of 5534 infants included in the study, 39 later died of SIDS. INTERVENTIONS: Multiple public health activities to reduce the prevalence of the prone infant sleeping position in Tasmania and verbal information on the association between prone position and SIDS to cohort participants from May 1, 1991. MAIN OUTCOME MEASURE: Sudden infant death syndrome incidence. RESULTS: The Tasmanian SIDS rate decreased (P < .01) from 3.8 (95% confidence interval [CI], 3.5 to 4.2) deaths per 1000 live births from 1975 through 1990 to a rate of 1.5 (95% CI, 0.9 to 2.2) deaths per 1000 live births in 1991 through 1992. The SIDS mortality rate in the cohort by period of birth was 7.6 (95% CI, 4.9 to 10.3) deaths per 1000 live births for those born from May 1, 1988, through April 30, 1991, and 4.1 (95% CI, 1.3 to 7.0) deaths per 1000 infants for those born from May 1, 1991, through October 31, 1992. The prevalence of usual prone sleeping position at 1 month of age was 29.9% and 4.3% in these two cohorts, respectively (adjusted odds ratio, 0.11; 95% CI, 0.08 to 0.13). Logistic regression demonstrated that 70% of the SIDS rate reduction in the cohort could be accounted for by the decreased prevalence of the prone sleeping position. Other factors examined individually contributed to less than 10% of the SIDS rate reduction. CONCLUSIONS: The major contributing factor to the recent SIDS rate decline in Tasmania has been the reduction in the proportion of infants usually sleeping prone.

Cohort Studies↗
PubMed1995

The Tasmanian SIDS Case-Control Study: univariable and multivariable risk factor analysis.

A population-based retrospective case-control study has been conducted in Tasmania since October 1988. Study measurements pertained to the scene of death of last sleep, as well as a verbal questionnaire on relevant exposures. From 1 October 1988 to 1 October 1991, 62 cases of sudden infant death syndrome (SIDS) occurred. Case response rate for retrospective interviews was 94% (58/62). The initial control response rate was 84% (101/121). After stratification for maternal age and birthweight, there was no increase in risk associated with the usual side position (odds ratio [OR] 1.05 [0.27, 5.02]), compared with the supine position (OR 1.00, reference). The prone position was associated with increased risk [OR 5.70 (1.67, 25.58)], relative to the supine position. In the final multivariable model, predictors of SIDS in this study were usual prone position (P < 0.001), maternal smoking (P = 0.008), a family history of asthma (P = 0.045) and bedroom heating during last sleep (P = 0.039). Protective factors were maternal age over 25 years (P = 0.013) and more than one child health clinic attendance (P = 0.003). The results provide further support for current health education activities which aim to inform parents of modifiable risk factors for SIDS, including the prone sleeping position, thermal stress and infant exposure to tobacco smoke.

Breast Feeding↗
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↗
PubMed1994

An assessment of the impact of public health activities to reduce the prevalence of the prone sleeping position during infancy: the Tasmanian Cohort Study.

BACKGROUND: An intervention to reduce the prevalence of the prone sleeping position during infancy was implemented in Tasmania particularly from 1991 onward. The purpose of this report is to assess the impact of public health activities in promoting avoidance of the prone infant sleeping position among cohort study participants. METHODS: The prospective cohort study involved the one-fifth of Tasmanian live births who are assessed perinatally as being at higher risk for Sudden Infant Death Syndrome (SIDS). From 1 January 1988 until 30 April 1992, 5,403 infants participated in the hospital (4 days postnatal age) and home interviews (5 weeks postnatal age) (88% of eligible infants). After the finding that cohort infants who usually slept prone were at significantly greater risk for SIDS, additional questions on awareness and choice of infant sleep position were asked. RESULTS: The proportion of infants usually sleeping prone declined from 29.9% in the cohort prior to publication of the cohort findings (1 May 1988-30 April 1991) to 5.4% in the post publication cohort (1 May 1991-30 April 1992), RR = 0.18 (0.15, 0.22). Teenage motherhood was associated with non-awareness (RR = 2.39 (1.41, 3.24)) of an association between prone position and SIDS. After adjusting for maternal age, nonawareness remained positively associated with maternal smoking, maternal education (< Year 12), and paternal unemployment, while mothers who read books to prepare for the baby and who were married were more likely to be aware. In the period after the cohort study publication, the most common reasons given for the usual prone position were that the baby preferred that position and slept better. CONCLUSION: Public health activities to reduce the prevalence of the prone sleeping position have had a significant impact, with a dramatic reduction in the proportion of cohort infants usually sleeping prone. The identification of characteristics of nonaware mothers and the reasons for choosing a particular sleeping position will be used to maintain and improve health education in this area.

Child, Preschool↗
PubMed1994

The relation between climatic temperature and sudden infant death syndrome differs among communities: results from an ecologic analysis.

We examined the negative relation between temperature and the sudden infant death syndrome (SIDS) in 22 communities in seven countries. We estimated the percentage increase in SIDS rate for a 1 degree C drop in climatic temperature. The relation differed substantially among communities. In New Zealand and Australia (10 communities), the association was consistently strong; in Europe (seven communities), it varied from strong to weak; and in the USA (five communities), it was moderate or weak. We postulate that low climatic temperature indirectly increases the incidence of SIDS, particularly in countries where outdoor climatic temperature modifies the indoor temperature and clothing habits.

Australia↗
PubMed1993

Factors potentiating the risk of sudden infant death syndrome associated with the prone position.

BACKGROUND: In several studies the sudden infant death syndrome (SIDS) has been significantly associated with sleeping in the prone position. It is not known how the prone position increases the risk of SIDS. METHODS: We analyzed data from a case-control study (58 infants with SIDS and 120 control infants) and a prospective cohort study (22 infants with SIDS and 213 control infants) in Tasmania. Interactions were examined in matched analyses with a multiplicative model of interaction. RESULTS: In the case-control study, SIDS was significantly associated with sleeping in the prone position, as compared with other positions (unadjusted odds ratio, 4.5; 95 percent confidence interval, 2.1 to 9.6). The strength of this association was increased among infants who slept on natural-fiber mattresses (P = 0.05), infants who were swaddled (P = 0.09), infants who slept in heated rooms (P = 0.006), and infants who had had a recent illness (P = 0.02). These variables had no significant effect on infants who did not sleep in the prone position. A history of recent illness was significantly associated with SIDS among infants who slept prone (odds ratio, 5.7; 95 percent confidence interval, 1.8 to 19) but not among infants who slept in other positions (odds ratio, 0.83). In the cohort study, the risk of SIDS was greater among infants who slept prone on natural-fiber mattresses (odds ratio, 6.6; 95 percent confidence interval, 1.3 to 33) than among infants who slept prone on other types of mattresses (odds ratio, 1.8). CONCLUSIONS: When infants sleep prone, the elevated risk of SIDS is increased by each of four factors: the use of natural-fiber mattresses, swaddling, recent illness, and the use of heating in bedrooms.

Bedding and Linens↗
PubMed1993

A comparison of prospective and retrospective responses on sudden infant death syndrome by case and control mothers.

Based on information from two studies of sudden infant death syndrome (SIDS) from 1988-1991 in Tasmania, Australia, prospective and retrospective maternal responses to an identical set of questions were compared for 27 cases and 25 controls. There was good agreement on demographic factors, maternal obstetric history, parental smoking, and infant feeding practices. Reported changes in sleep habits were slightly greater for cases, and further work is needed to determine if this reflects recall bias or real changes during early infant life. Case mother reports regarding family history of disease and infant bedding were more discrepant, suggesting recall bias and supporting prospective collection of this information.

Bias↗