Prone sleeping position and SIDS: evidence from recent case-control and cohort studies in Tasmania

The most recent data from the cohort and case-control studies of SIDS and prone position recently reported from Tasmania are reviewed. The cohort analysis was based on 4103 infants born between 1 January 1988 and 1 December 1990 assessed as being at high risk at birth, of whom 29 later died of SIDS. A matched analysis which controlled for infant birthweight and maternal age indicated that prone sleeping position was associated with an increased risk of SIDS (OR 3.92, 95% Cl [1.37-11.24]). The case-control study was based on all (n = 55) Tasmanian SIDS death from October 1989 to April 1991 and matched live controls. The unadjusted odds ratio for prone position and SIDS was 5.04 (95% Cl [2.29-11.11]). The population attributable risk percentage, based on the high risk cohort data, was 0.38 (95% Cl [0.35-0.41]), suggesting that a significant reduction in SIDS incidence might occur if the prevalence of the prone sleeping position in the infant population were reduced. Other factors which may be important for the development of any public health interventions to reduce SIDS based on these findings are discussed.

Industrial accidents are produced by social relations of work: a sociological theory of industrial accidents

Industrial accidents are produced by social relations work. This sociological explanation of accidents differs from the hypotheses on which the majority of modern safety practices are based, which reduce accident causes to unsafe acts and unsafe conditions. Accidents are seen as produced at each of three levels of social relations of work (rewards, command and organisation), and also non-socially at the individual-member level. The resulting hypotheses were tested using data collected according to a semi-experimental design in seven plants in which shift (day/night), shift type (rotating/fixed), technological type and management styles were the factors controlled for. Because of the design, machines, materials and, in most cases, workers were the same across shifts and social relations varied. The sociological theory proved capable of explaining most of the variation in inter-shift differences in accident rates, and, when tested statistically, appeared to have greater explanatory power than competing hypotheses. It is concluded that accidents can be prevented by workers who exercise auto-control at all levels and by management which, in the absence of worker orientations favourable to auto-control, engages in safety management as defined sociologically. A practical consequence for ergonomics is that when plant, equipment and processes are to be modified, an attempt to understand their interaction with the social relations of work should be made. A theoretical consequence is that sociological insights should be incorporated into the perspective of the ergonomics discipline.

Prospective cohort study of prone sleeping position and sudden infant death syndrome

Studies of the link between prone sleeping position and sudden infant death syndrome have been criticised on grounds of recall bias and for not taking into account possible confounding effects. To avoid recall bias and to allow measurement of important biological factors a prospective cohort study of the cause of sudden infant death syndrome (SIDS) is being conducted. The infants included are those at high risk of the syndrome as assessed by a perinatal score. Of the 3110 members of the cohort born between January, 1988, and end of March, 1990, 23 infants later died of SIDS. Sleep position information was available for 15 of these. Matched analysis to control for the confounding effects of infant birthweight and maternal age indicated that prone sleeping position was associated with an increased risk of SIDS (OR 4.47 95% Cl [1.30-15.43]). The findings are strengthened by the results of a concurrent retrospective case-control study of 42 SIDS cases in which the prone position was also associated with an increased risk of SIDS (unadjusted OR 3.45 [1.59-7.49]).

Assessing school health education programs

This review focuses on the component of health education directed at achieving changes in health behavior. Much of the work in this field has centered on health behavior that has a role in preventing future disease. Because the evidence is strongest in relation to coronary heart disease (17), considerable effort has been devoted to this area. Walter et al. (34) indicated that the most relevant forms of health behavior to be considered in school-based programs on heart disease are those relating to diet, physical activity, and smoking. Programs relating to each of these behaviors are addressed here.

The development of a model for predicting infants at high risk of sudden infant death syndrome in Tasmania

A statutory 'Notification of Birth' form, containing obstetric and perinatal information, has been routinely collected for Tasmanian deliveries since 1974. For the period 1980 to 1984, birth notification data was collected for over 99% of Tasmanian deliveries. This data was examined for the 130 cases of sudden infant death syndrome (SIDS) that occurred from 1980 to 1984 and for 610 controls. It was then used to construct an at-birth scoring system to predict infants at higher risk of SIDS in the postneonatal period. A predictive model of the relative risk of SIDS was developed by fitting a binomial/logistic generalised linear model to the binary 1980-1984 case control data with birth variables used as predictors. The final predictive model contained five variables (maternal age, infant sex, birth weight, month of birth and feeding practice) and had a sensitivity of 62% and specificity of 73%. The model was then tested on independent birth cohorts from 1985 and 1986 and found to have a sensitivity of 47% and specificity of 77%. The risk of SIDS in the group of infants classified as high risk was 7.9 per 1000 live births and in the group at low risk it was 2.5 per 1000 live births. In addition, the model predicted 74% of neonatal deaths occurring during these 2 years. This compares well with other predictive models developed elsewhere. The predictive model will be used to identify infants at high risk for SIDS in a prospective cohort study.

Differences in modifiable cardiovascular disease risk factors in Australian schoolchildren: the results of a nationwide survey

Two thousand four hundred schoolchildren ages 9, 12, and 15 years were randomly selected to participate in the Health and Fitness Survey of Australian Schoolchildren in 1985. Data on blood lipids, aerobic fitness, blood pressure, and obesity were obtained through physical measurement. Information on socioeconomic status and ethnic origin was collected via questionnaire. Serum total cholesterol and low and high-density lipoprotein cholesterol were lowest in the oldest age group. Girls had significantly higher serum lipid levels, the difference being greatest at 15 years. However, comparison of the total cholesterol/high-density lipoprotein cholesterol ratio showed a trend in the direction of decreasing risk with increasing age for girls, with the reverse being found in boys. Fifteen-year-old girls were also the fattest and least fit of all the children, but had significantly lower systolic and diastolic blood pressures than their male peers. Children of Asian ethnic origin had significantly lower systolic and diastolic blood pressures and a significantly higher mean high-density lipoprotein cholesterol and were less likely to be overweight compared with other ethnic groups. Children from Mediterranean/Middle-East countries were significantly fatter and had a higher mean diastolic blood pressure than the other ethnic groups. These differences were detectable at age 9 years. Children from lower socioeconomic backgrounds were fatter and had a significantly lower mean high-density lipoprotein cholesterol and higher mean serum triglyceride levels. As with ethnic origin, these differences were detectable at age 9 years. The results demonstrate that age, sex, ethnic origin, and socioeconomic status can be used as variables to describe mean differences in the levels of cardiovascular risk factors in the national population of children. As some elevations in risk factors appear to be present in the youngest age group and these levels correlate with fatty streak and fibrous plaque formation in young adulthood, preventive programs should aim at intervention prior to puberty.

Cigarette smoking in Australian schoolchildren

Six thousand, four hundred and fifty-one schoolchildren who were aged nine to 15 years completed a questionnaire about their patterns of cigarette use, as part of the nation-wide Health and Fitness Survey of Australian Schoolchildren which was conducted in 1985. The survey yielded figures for the prevalence of cigarette smoking by age, sex, socioeconomic status and ethnic origin. It also provided data on the relationship between parental smoking and smoking in children. By the age of 15 years, 32.4% of the girls and 26.0% of the boys in the study sample had smoked at least one cigarette in the seven days before they were surveyed. In some of the age-groups, the average number of cigarettes that were consumed by girl smokers equalled or exceeded that of their male counterparts. There were no significant differences in the prevalence of current cigarette smoking with differences in socioeconomic status. This finding contrasts with the pattern of use in adults. Ethnic origin was a statistically-significant predictor of smoking behaviour in children. Significantly-fewer children of Asian ethnic origin were current smokers. Parental smoking status also appeared to be an important determinant of smoking behaviour in schoolchildren. This influence was more important for girls than for boys, particularly when the mother was a smoker. The over-all findings suggest that many features of the adult pattern of cigarette use are established by the age of 15 years. The findings also supported the trend towards increased cigarette consumption by girls compared with boys that was noted by earlier researchers. These findings should encourage a serious reappraisal of the role of cigarette advertising in the promotion of smoking in young persons.

Fall in coronary heart disease mortality in U.S.A. and Australia due to sudden death: evidence for the role of polyunsaturated fat

Epidemiological studies have been reviewed which provide suggestive evidence of an association between the fall in coronary heart disease mortality in the U.S.A and Australia since 1967, characterized by a fall in sudden deaths, to the increase in polyunsaturate fat consumption that has occurred in both countries since 1960. This association led directly in the same institution to carefully designed experimental studies undertaken in the rat, and a non-human primate, the marmoset (Callithrix jacchus jacchus) with a heart and lipid metabolism more closely resembling that of man. In both animal species, a vegetable fat diet had a protective effect against the increase in contractility of isolated papillary muscles induced by age, the addition of animal fat, or by isoprenaline in vitro. Similar effects were observed following coronary artery ligation, where the extent of dysrhythmia was greatly reduced by supplementing the diet with a linoleic acid rich vegetable oil. It is concluded that the combination of epidemiological and experimental evidence indicates a protective effect of dietary polyunsaturates against sudden cardiac death. This work illustrates the value of the integration of epidemiological and experimental approaches to the aetiology of disease.

Targeting the smoker in an anti-smoking campaign

Between May and September 1983, 1,661 smokers from a random sample of the populations of Sydney and Melbourne were interviewed in their homes. Of the first group, 219 were followed up 12 months later, representing a 75% response rate. Intention, measured by perceived likelihood to quit, was validated as a predictor of a later attempt to quit smoking in the cohort study. Males reported likelihood to quit more often than females. Perceived importance of smoking as a community health problem was also important in predicting attempts to change smoking status, indicating the possible importance of an agenda-setting role for the mass media in promoting change. The key finding was the interaction between health beliefs and social influence in predicting level of intention. On their own, health beliefs showed no relationship to perceived likelihood to quit, and social influence could be counterproductive. However, taken together, these two variables were strongly predictive of change. This suggests that a combination of these two messages should be used in anti-smoking campaigns.

Alcohol consumption and the risk of alcohol related cirrhosis in women

The risks in women of cirrhosis with a likely primary alcohol aetiology were estimated for various levels of alcohol consumption in a case-control study. Data were obtained from 41 women with a first diagnosis of cirrhosis who had no evidence of non-alcohol-related cirrhosis; three matched controls were interviewed for each case. Significant increases in the risk of cirrhosis were detected at levels of consumption between 41 and 60 g daily; above this level a dose-response relation was observed. The risk of cirrhosis did not appear to be influenced by other nutritional factors or history of liver disease or use of hepatotoxic drugs. One per cent of Australian women consume more than 40 g alcohol daily, yet more than 90% of women identified with cirrhosis consumed alcohol at this level. Preventive interventions to reduce alcohol consumption in the small group of women who consume more than 40 g daily have the potential to reduce substantially the incidence of alcohol related cirrhosis.

Chylomicrons and chylomicron remnants in coronary artery disease: a case-control study

Epidemiologic studies of coronary artery disease have largely overlooked the role of triglyceride-rich lipoproteins circulating in the post-prandial state. We have conducted a case-control study in males which examined fasting plasma lipoproteins and lipoproteins circulating 4 h after ingestion of a test meal containing fat and cholesterol. The cases were 82 subjects with coronary artery disease confirmed by angiography, while there were two control groups: one group of 38 'hospital controls' free of significant coronary disease by angiography, and a second group of 61 'workforce controls' free of coronary disease on historical grounds. Mean plasma and LDL cholesterol levels were significantly higher and HDL cholesterol levels were significantly lower in cases than in controls. The apo-B48/apo-B100 ratio in lipoproteins Sf greater than 60 obtained 4 h post-prandially, a relative measure of chylomicron and remnant presence, was significantly higher in cases than in controls. After pooling of all data, the prevalence of coronary artery disease was found to increase progressively with the concentration of plasma cholesterol and triglycerides, total cholesterol/HDL cholesterol ratio and the apo-B48/apo-B100 ratio in Sf greater than 60, the relative risk being highest for total cholesterol/HDL cholesterol ratio. After controlling for the confounding effects of age and other lipid factors via multiple logistic regression, apo-B48/apo-B100 ratio was still a significant predictor of coronary artery disease presence (z = 1.97, P less than 0.05) in a 'dose-response' fashion. The risk of coronary artery disease in the top quartile of apo-B48/apo-B100 distribution was 2.2-fold greater than that for the bottom quartile, after adjustment for the effects of other risk factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Uptake and quitting smoking trends in Australia 1974-1984

Five cross-sectional surveys of random, cluster samples of the Australian population taken between 1974 and 1984 obtained information on the prevalence of smokers and ex-smokers. This information, however, does not provide the essential data for trend studies of smoking behavior: Estimates of the prevalence of smoking uptake and of smoking cessation are also required. The uptake rate for males ages 16-19 reached a peak in 1980. For females ages 16-19, the uptake rate reached a peak in 1983; in 1984 there was a significant drop in the percentage of female ever-smokers, which coincidentally corresponded to the introduction of large-scale, mass-media anti-smoking campaigns in Australia. A quit ratio has been defined in this study as the ratio of the proportion of ex-smokers to the proportion of those available to quit, that is, ever-smokers. This ratio enables community smoking cessation activity trends to be plotted. Quit ratios were similar for both sexes and increased at approximately 1% per year for almost all age groups studied. Overall, the percentage increase between 1974 and 1984 was greater for females than for males.

Cotinine validation of self-reported smoking in commercially run community surveys

A validation study was carried out on self-reported smoking for 1177 people in Sydney and Melbourne in 1983. Because of its long half life and the fact that smoking is its only source in body fluids, saliva cotinine was chosen as the validation measure. Cotinine levels above 250 nmol/l were used to classify people as smokers. The sensitivity of self-reported smoking was 92.6% and the specificity was 93.4%. There was some evidence that people in the process of changing their smoking status might be slow in updating their self-classification. The smoking prevalence estimate based on cotinine levels was found to be 1.7% lower than that for self-reported smoking status. The small proportion of false negatives and false positives suggests that commercially collected data banks can be valid sources of prevalence data. Correlation between cotinine level and reported cigarette consumption was not affected by sample volume, and was similar to that achieved for carbon monoxide and thiocyanate at a low 0.34. Regression analysis using self-reported cigarette consumption filter/non-filter cigarettes, and time since last cigarette as predictors, explained 13.6% of the variance in cotinine level.

Evaluation of the Sydney "Quit. For Life" anti-smoking campaign. Part 2. Changes in smoking prevalence

Between June and November 1983, the "Quit. For Life" media campaign was conducted in Sydney to reduce the prevalence of smoking. Surveys on a cross-sectional sample of the Sydney population were conducted before and after the campaign, and similar measures were undertaken in the rest of Australia for comparison. The sample sizes for both the Sydney and control areas comprised more than 4000 subjects. In addition, a cohort of 949 residents of Sydney and Melbourne were followed for changes in the prevalence of smoking during the year of the campaign. The cross-sectional survey results for 1984 and 1983 demonstrated decreases in the prevalence of smoking of approximately 1% for both men and women in Sydney compared with the rest of Australia. In the cohort study there was a 3.4% decrease in smoking prevalence in Sydney compared with a 0.8% increase in Melbourne. The pooled estimate of the difference in smoking prevalence attributable to the campaign was 2.8% (95% confidence interval, 0.5%-5.1%).

Evaluation of the Sydney "Quit. For Life" anti-smoking campaign. Part 1. Achievement of intermediate goals

The "Quit. For Life" campaign was a media-based programme that was aimed at reducing the prevalence of smoking in Sydney. The programme committee set four intermediate goals which it felt had to be met for such a change in prevalence to occur. From households selected at random in Sydney and Melbourne, 5713 people were interviewed to assess whether the campaign attained these goals. The television commercials that were designed for the campaign, their frequency and the timing of their screening produced a higher recall of the commercial's message and the use of campaign back-up services than were specified originally in the goals. During the campaign there was a progressive increase in the number of smokers in Sydney who reported that they were likely to quit; this was significantly different from Melbourne data by the end of the campaign and thus fulfilled another campaign goal. However, shortly after the campaign ended, the proportion of smokers who intended to quit smoking was the same in the two cities. A cohort study of 949 people from the baseline study showed that, during the 12-month period of follow-up, 66% of Sydney smokers tried to stop or to reduce their smoking. In the control city, Melbourne, 60% of smokers reported making such attempts. Of the original smokers, 23% in Sydney and 9% in Melbourne quit during the follow-up period--a statistically significant difference. As well, 10% of the original ex-smokers in Sydney and 11% in Melbourne relapsed, while 4% of nonsmokers in both cities began smoking by the end of the second survey.