Exhaled breath condensate: methodological recommendations and unresolved questions

Collection of exhaled breath condensate (EBC) is a noninvasive method for obtaining samples from the lungs. EBC contains large number of mediators including adenosine, ammonia, hydrogen peroxide, isoprostanes, leukotrienes, nitrogen oxides, peptides and cytokines. Concentrations of these mediators are influenced by lung diseases and modulated by therapeutic interventions. Similarly EBC pH also changes in respiratory diseases. The aim of the American Thoracic Society/European Respiratory Society Task Force on EBC was to identify the important methodological issues surrounding EBC collection and assay, to provide recommendations for the measurements and to highlight areas where further research is required. Based on the currently available evidence and the consensus of the expert panel for EBC collection, the following general recommendations were put together for oral sample collection: collect during tidal breathing using a noseclip and a saliva trap; define cooling temperature and collection time (10 min is generally sufficient to obtain 1-2 mL of sample and well tolerated by patients); use inert material for condenser; do not use resistor and do not use filter between the subject and the condenser. These are only general recommendations and certain circumstances may dictate variation from them. Important areas for future research involve: ascertaining mechanisms and site of exhaled breath condensate particle formation; determination of dilution markers; improving reproducibility; employment of EBC in longitudinal studies; and determining the utility of exhaled breath condensate measures for the management of individual patients. These studies are required before recommending this technique for use in clinical practice.

Past exposure to sun, skin phenotype, and risk of multiple sclerosis: case-control study

OBJECTIVE

To examine whether past high sun exposure is associated with a reduced risk of multiple sclerosis.

DESIGN

Population based case-control study.

SETTING

Tasmania, latitudes 41-3 degrees S.

PARTICIPANTS

136 cases with multiple sclerosis and 272 controls randomly drawn from the community and matched on sex and year of birth.

MAIN OUTCOME MEASURE

Multiple sclerosis defined by both clinical and magnetic resonance imaging criteria.

RESULTS

Higher sun exposure when aged 6-15 years (average 2-3 hours or more a day in summer during weekends and holidays) was associated with a decreased risk of multiple sclerosis (adjusted odds ratio 0.31, 95% confidence interval 0.16 to 0.59). Higher exposure in winter seemed more important than higher exposure in summer. Greater actinic damage was also independently associated with a decreased risk of multiple sclerosis (0.32, 0.11 to 0.88 for grades 4-6 disease). A dose-response relation was observed between multiple sclerosis and decreasing sun exposure when aged 6-15 years and with actinic damage.

CONCLUSION

Higher sun exposure during childhood and early adolescence is associated with a reduced risk of multiple sclerosis. Insufficient ultraviolet radiation may therefore influence the development of multiple sclerosis.

Associations of TV viewing and physical activity with the metabolic syndrome in Australian adults

AIMS/HYPOTHESIS

We analysed a sample of Australian adults to determine the strength of associations of TV viewing and participation in physical activity with the metabolic syndrome.

METHODS

This population-based cross-sectional study included 6,241 adults aged > or =35 years who were free from diagnosed diabetes mellitus and self-reported ischaemic disease and were not taking lipid-lowering or antihypertensive drugs. The metabolic syndrome was defined according to the 1999 World Health Organization criteria. Participants self-reported TV viewing time and physical activity time for the previous week.

RESULTS

The adjusted odds ratio of having the metabolic syndrome was 2.07 (95% CI 1.49-2.88) in women and 1.48 (95% CI 0.95-2.31) in men who watched TV for >14 h per week compared with those who watched < or =7.0 h per week. Compared with those who were less active (<2.5 h per week), the odds ratio for the metabolic syndrome was 0.72 (95% CI 0.58-0.90) in men and 0.53 (95% CI 0.38-0.74) in women who were active (> or =2.5 h per week). Longer TV viewing (>14 h per week) was associated with an increased risk of insulin resistance, obesity and dyslipidaemia in both men and women. A total physical activity time of > or =2.5 h per week was associated with a reduced prevalence of both insulin resistance and dyslipidaemia in both sexes and reduced prevalence of both obesity and hypertension in women.

CONCLUSIONS/INTERPRETATION

Increased TV viewing time was associated with an increased prevalence of the metabolic syndrome, while physical activity was associated with a reduced prevalence. Population strategies addressing the metabolic syndrome should focus on reducing sedentary behaviours such as TV viewing, as well as increasing physical activity.

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.

Vitamin D levels in people with multiple sclerosis and community controls in Tasmania, Australia

BACKGROUND

Adequate 25(OH)D levels are required to prevent adverse effects on bone health. Population-based data on factors associated with 25(OH)D levels of people with MS have been lacking.

OBJECTIVES

To examine the prevalence and determinants of vitamin D insufficiency in a population-based sample of MS cases and controls, and to compare 25(OH)D status between MS cases and controls, taking into account case disability.

METHODS

We conducted a population based case-control study in Tasmania, Australia (latitude 41-43 degrees S) on 136 prevalent cases with MS confirmed by magnetic resonance imaging and 272 community controls, matched on sex and year of birth. Measurements included serum 25(OH)D, sun exposure, skin type, dietary vitamin D intake and disability including EDSS.

RESULTS

A high prevalence of vitamin D insufficiency was found in MS cases and controls. Among MS cases, increasing disability was strongly associated with lower levels of 25(OH)D and with reduced sun exposure. Cases with higher disability (EDSS > 3) were more likely to have vitamin D insufficiency than controls (OR = 3.07 (1.37, 6.90) for 25(OH)D </= 40 nmol/l), but cases with low disability were not (OR = 0.87 (0.41, 1.86)).

CONCLUSION

The strong associations between disability, sun exposure and vitamin D status indicate that reduced exposure to the sun, related to higher disability, may contribute to the high prevalence of vitamin D insufficiency found in this population-based MS case sample. Active detection of vitamin D insufficiency among people with MS and intervention to restore vitamin D status to adequate levels should be considered as part of the clinical management of MS.

Prevalence and concurrence of anxiety, depression and fatigue over time in multiple sclerosis

BACKGROUND

Anxiety, depression and fatigue are commonly reported by persons with multiple sclerosis (PwMS).

OBJECTIVES

We estimated the prevalence of each factor in a representative sample of PwMS, and in subgroups defined by age, sex and disease duration, at cohort entry and over time. We further examined whether and how these factors clustered together.

METHODS

A population-based longitudinal cohort of 198 PwMS was followed 6-monthly for 2.5 years. The Hospital Anxiety and Depression Scale (HADS) was used to measure anxiety (cut-point >7) and depression (>7) and the Fatigue Severity Scale (FSS) to measure fatigue (≥5).

RESULTS

At cohort entry, prevalence of anxiety was 44.5% (95%CI 37-51%), depression 18.5% (95%CI 12.6-23.4%), and fatigue 53.7% (95%CI 47-61%). Fatigue was more common in males than females (RR 1.29, p=0.01), with attenuation of the effect after adjustment for Expanded Disability Status Scale (adjusted RR 1.18, p=0.13). Prevalence of anxiety (but not depression or fatigue) decreased by 8.1% per year of cohort observation (RR 0.92, 95%CI 0.86-0.98, p=0.009), with the effect more pronounced in women (14.6%, RR 0.85, 95%CI 0.79-0.93, -<0.001) than men (2.6%, RR 1.03, 95%CI 0.90-1.17, p=0.77). There was no apparent seasonal variation in the prevalence of any of the three factors (p>0.05). All three factors occurred contemporaneously at cohort entry in a higher proportion of the cohort than expected by chance (p<0.001).

CONCLUSIONS

Anxiety, depression and fatigue are common in PwMS and tend to cluster together. The findings are important for clinical management of PwMS and to the exploration of possible shared causal biological pathways.

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]).

Regional variation in multiple sclerosis prevalence in Australia and its association with ambient ultraviolet radiation

The aim of this study was to conduct an ecological analysis of the extent to which ultraviolet radiation (UVR) levels might explain the regional variation of multiple sclerosis (MS) in Australia. MS prevalence data for six Australian regions were compared with UVR levels of the largest city in each region, with some other climatic variables and with the melanoma incidence in the same regions. A close association was found between the theoretical MS prevalence predicted from UVR levels and the actual prevalence. Furthermore, the negative correlation between UVR and MS prevalence (r = -0.91, p = 0.01) was higher than the positive correlation observed for UVR and malignant melanoma incidence (r = 0.75, p = 0.15 for males and r = 0.80, p = 0.10 for females). This study demonstrated that the regional variation in MS prevalence in the continent of Australia could be closely predicted by regional UVR levels. It is consistent with the hypothesis that UVR exposure may reduce the risk of MS possibly via T-lymphocyte-mediated immunosuppression. Analytical epidemiology studies are required to investigate this specific hypothesis.

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)

An investigation of the effects of daily physical activity on the health of primary school students in South Australia

Studies of the health effects of a daily physical activity programme have been carried out in 10-year-old school children in Adelaide, South Australia. In the first phase (1978) observations on endurance fitness, four skin folds, blood pressure and blood lipids were made before and after a randomized trial over a period of 14 weeks. Comparisons were made on over 500 children drawn from classes in seven Primary schools involved in an endurance fitness programme (1 1/4 hours per day), a skill programme and the previous physical education programme (controls). The fitness group experienced significant gains in physical work capacity (PWC) and showed significant decreases in body fat compared to the other two groups. No significant differences were observed in plasma cholesterol, triglycerides and HDL cholesterol. Subsequently in the second phase (1980) observations were made on a group of 216 10-year-old children who had already experienced two years of the physical activity programme adopted after phase one. Comparison with the observations in the 10-year-old children in 1978 made prior to the intervention revealed significantly smaller skin folds and greater PWC, with lower blood pressure reaching statistical significance for diastolic pressure in boys. The findings suggest beneficial effects on health of daily physical activity programmes within existing primary school curricula. There was no evidence of any loss of academic performance as measured by arithmetic and reading tests in spite of 45-60 minutes' loss of formal teaching time each day.

Thermal environment and sudden infant death syndrome: case-control study

OBJECTIVE

To compare the thermal environment of infants who died of the sudden infant death syndrome with that of age matched control infants.

DESIGN

Case-control study. Infants who died were matched with two controls, one for age and one for age and birth weight. Thermal measurements were conducted at the death scene for cases and at the scene of last sleep for control infants, who were visited unexpectedly within four weeks of the index infant's death on a day of similar climatic conditions. A follow up questionnaire was administered to parents of cases and controls.

SETTING

The geographical area served by the professional Tasmanian state ambulance service, which includes 94% of the Tasmanian population.

SUBJECTS

41 infants died of the sudden infant death syndrome at home; thermal observations at death scene were available for 28 (68%), parental questionnaire data were available for 40 (96%). 38 controls matched for age and 41 matched for age and birth weight.

RESULTS

Cases had more excess thermal insulation for their given room temperature (2.3 togs) than matched controls (0.6 togs) (p = 0.009). For every excess thermal insulation unit (tog) the relative risk of the sudden infant death syndrome was 1.26 (95% confidence interval 1.05 to 1.52). The average thermal bedding value calculated from parental recall was similar to that observed by attendant ambulance officers (mean difference = 0.4 tog, p = 0.39). Cases were more likely to have been found prone (odds ratio 4.58; 1.48 to 14.11). Prone sleeping position was not a confounder or effect modifier of the relation between excess thermal insulation and the syndrome.

CONCLUSIONS

Overheating and the prone sleeping position are independently associated with an increased risk of the sudden infant death syndrome. Further work on infant thermal balance and sudden infant death is required and guidelines for appropriate infant thermal care need to be developed.

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.

Offspring number, pregnancy, and risk of a first clinical demyelinating event: the AusImmune Study

OBJECTIVE

To examine the association between past pregnancy, offspring number, and first clinical demyelination risk.

METHODS

Cases (n = 282) were aged 18-59 years with a first clinical diagnosis of CNS demyelination (first clinical demyelinating event [FCD]) and resident within 1 of 4 Australian centers (from latitudes 27° south to 43° south) from 2003 to 2006. Controls (n = 542) were matched to cases on age, sex, and study region, without first clinical diagnosis of CNS demyelination.

RESULTS

Higher offspring number was associated with FCD risk among women (p < 0.001) but not men (p = 0.71); difference in effect; p = 0.001. Among women, higher parity was associated with reduced risk of FCD (adjusted odds ratio 0.51 [95% confidence interval 0.36, 0.72] per birth) with a similar magnitude of effect observed among classic first demyelinating events (adjusted odds ratio 0.47 [95% confidence interval 0.29, 0.74]). The apparent beneficial effect of higher parity was also evident among parous women only (p < 0.001). Among cases, a clear female excess was evident for those with low but not high (4 or more) offspring number. Factors such as human leukocyte antigen DR15 genotype did not appear to modify the association between higher parity and a reduced FCD risk among women.

CONCLUSIONS

These findings are consistent with a cumulative beneficial effect of pregnancy. Temporal changes toward an older maternal age of parturition and reduced offspring number may partly underlie the increasing female excess among MS cases over time.

Combined effects of smoking, anti-EBNA antibodies, and HLA-DRB1*1501 on multiple sclerosis risk

OBJECTIVE

To examine the interplay between smoking, serum antibody titers to the Epstein-Barr virus nuclear antigens (anti-EBNA), and HLA-DR15 on multiple sclerosis (MS) risk.

METHODS

Individual and pooled analyses were conducted among 442 cases and 865 controls from 3 MS case-control studies-a nested case-control study in the Nurses' Health Study/Nurses' Health Study II, the Tasmanian MS Study, and a Swedish MS Study. Conditional logistic regression models were used to calculate odds ratios (ORs) and 95% CIs for the association between smoking, anti-EBNA titers, HLA-DR15, and MS risk. Study estimates were pooled using inverse variance weights to determine a combined effect and p value.

RESULTS

Among MS cases, anti-EBNA titers were significantly higher in ever smokers compared to never smokers. The increased risk of MS associated with high anti-EBNA Ab titers was stronger among ever smokers (OR = 3.9, 95% CI = 2.7-5.7) compared to never smokers (OR = 1.8, 95% CI = 1.4-2.3; p for interaction = 0.001). The increased risk of MS associated with a history of smoking was no longer evident after adjustment for anti-EBNA Ab titers. No modification or confounding by HLA-DR15 was observed. The increased risk of MS associated with ever smoking was only observed among those who had high anti-EBNA titers (OR = 1.7, 95% CI = 1.1-2.6).

CONCLUSIONS

Smoking appears to enhance the association between high anti-EBNA titer and increased multiple sclerosis (MS) risk. The association between HLA-DR15 and MS risk is independent of smoking. Further work is necessary to elucidate possible biologic mechanisms to explain this finding.

Validity and reliability of adult recall of past sun exposure in a case-control study of multiple sclerosis

BACKGROUND

Measurement of past sun exposure through recall by adults has the potential for measurement error. We aimed to investigate aspects of validity and reliability of self-reported past sun exposure.

METHODS

A population-based case-control study was conducted in Tasmania on 136 cases with multiple sclerosis and 272 age- and sex-matched community controls. Repeat interviews on 52 cases and 52 controls were done on average 11 weeks after the initial interview. Sun exposure was assessed by questionnaire and lifetime calendar. Other measurements included serum 25-hydroxyvitamin D, actinic damage, and skin phenotype.

RESULTS

There was an association between recent sun exposure and serum vitamin D (time in the sun: r = 0.22, P < 0.01; activities outside: r = 0.31, P < 0.01 for controls) and between lifetime sun exposure and actinic damage [correlation between 0.34 (P < 0.01) and 0.17 (P = 0.01) for controls]. The test-retest weighted kappa statistic of self-reported sun exposure ranged from 0.43 to 0.74. Recall of childhood/adolescent sun exposure by standardized questioning was no less reproducible than recall of recent adult sun exposure and no less reliable when made with the calendar method. Comparing the questionnaire and calendar method, the measures of childhood/adolescent sun exposure had a similar predictive validity for multiple sclerosis.

CONCLUSIONS

The results of this study provide further evidence that adults are able to recall past sun exposure with shown validity and reliability and present information about the possible reasons for the good reliability of recalled sun exposure measures.

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.

Physiotherapy for cystic fibrosis in Australia and New Zealand: A clinical practice guideline

Physiotherapy management is a key element of care for people with cystic fibrosis (CF) throughout the lifespan. Although considerable evidence exists to support physiotherapy management of CF, there is documented variation in practice. The aim of this guideline is to optimize the physiotherapy management of people with CF in Australia and New Zealand. A systematic review of the literature in key areas of physiotherapy practice for CF was undertaken. Recommendations were formulated based on National Health and Medical Research Council (Australia) guidelines and considered the quality, quantity and level of the evidence; the consistency of the body of evidence; the likely clinical impact; and applicability to physiotherapy practice in Australia and New Zealand. A total of 30 recommendations were made for airway clearance therapy, inhalation therapy, exercise assessment and training, musculoskeletal management, management of urinary incontinence, managing the newly diagnosed patient with CF, delivery of non-invasive ventilation, and physiotherapy management before and after lung transplantation. These recommendations can be used to underpin the provision of evidence-based physiotherapy care to people with CF in Australia and New Zealand.

A comparison of trends of coronary heart disease mortality in Australia, USA and England and Wales with reference to three major risk factors-hypertension, cigarette smoking and diet

A comparison has been made of the recent changes in coronary heart disease mortality in Australia, the USA, and in the United Kingdom (England and Wales). Sharp declines in mortality dating from 1966 in Australia and from 1968 in the USA in both sexes contrast with a persistent increase in men in England and Wales until 1972 (after which a sight fall occurred) and a consistent slight fall in women since 1950. An investigation has been made of changes in 3 major risk factors-hypertension, cigarette smoking and diet in the 3 countries in an attempt to determine to what extent such changes might correlate with the different patterns of mortality. There has been a progressive and similar fall in mortality due to hypertension in both sexes in all 3 countries since 1950. There was a rise in cigarette smoking in all 3 countries from 1947 followed by a fall in the USA from 1963 and a more recent fall in men in Australia. There has been a levelling off of smoking in the United Kingdom in middle-aged and older men but not in women where smoking rates have increased from 1950 since when there has been a progressive slight fall in overall coronary heart disease mortality (although there is evidence of a recent rise in younger women.) Changes in dietary constituents (meat, eggs, milk and cheese, butter or margarine) have been examined by reference to aggregate consumption data. In Australia and the USA increases in vegetable fat consumption have occurred since 1950 with a reduction in animal fat in Australia but not in the USA. In the United Kingdom increases in vegetable fat have not been observed while there has been some increase in animal fat. It is concluded that the different patterns of coronary heart disease mortality in the 3 countries do correlate to some extent with changes in diet and cigarette smoking.

Within pair association between birth weight and blood pressure at age 8 in twins from a cohort study

OBJECTIVES

To study the association between birth weight and blood pressure in children from multiple pregnancies (multiplets), mostly twins, to determine whether maternal or genetic factors are responsible for the association.

DESIGN

Cohort study.

SETTING

Southern Tasmania.

SUBJECTS

888 children including 104 multiplets (32 monozygotic, 72 dizygotic).

MAIN OUTCOME MEASURE

Systolic blood pressure (mm Hg).

RESULTS

Blood pressure decreased with birth weight and increased with current body mass. After adjustment for age and body mass, systolic blood pressure changed by -1.94 mm Hg (95% confidence interval -2.89 to -0.98) per 1 kg increase in birth weight of singletons. For multiplets, blood pressure changed by -7.0 mm Hg (-10.1 to -3.9) for each 1 kg increase in birth weight. This was little altered in within pair analyses (-5.3, -13.8 to 3.2) and was similar for both monozygotic (-6.5, -22.5 to 9.4) and dizygotic (-4.9, -15.8 to 6.0) pairs.

CONCLUSION

Because the association between birth weight and blood pressure was largely unchanged in within pair analyses, exposures originating in the mother (such as nutritional status) cannot be wholly responsible. The association also remained within monozygotic pairs, suggesting that genetic predisposition is not wholly responsible either. The principal causal pathway must concern mechanisms within the fetoplacental unit. The stronger association in multiplets suggests that factors adversely influencing both blood pressure and birth weight are more prevalent in multiple pregnancies.

Maternal smoking and congenital malformations: an epidemiological study

In a case-control study undertaken in several hospitals in Connecticut, it was found that women who reported smoking more than 20 cigarettes a day during pregnancy had a relative risk of about 1.6 for congenital malformations in the offspring of that pregnancy compared with women who said they had not smoked at all during pregnancy. However, there was no significant increase in risk among women who reported smoking 20 or fewer cigarettes a day during pregnancy compared with those who said they had not smoked at all during pregnancy. The higher risk among moderate and heavy smokers could not be attributed to any of the potentially confounding variables considered in this study; furthermore, it was specific to smoking during pregnancy rather than before pregnancy, and increased with the average amount smoked a day. Nevertheless, because the increase in risk was modest, because response bias could exist in a study of this type, and because no other studies have examined in detail the smoking-congenital malformation hypothesis, further research is needed to determine whether the relationship between maternal smoking and congenital malformations in offspring is causal.

The Australian Schools Health and Fitness Survey. Physical fitness related to blood pressure but not lipoproteins

BACKGROUND

Recent research indicates that levels of conventional coronary heart disease risk factors in children are related to the premature development of atheroma. It is therefore important to determine how risk factors might be modified on a population scale in children.

METHODS AND RESULTS

In 1985, the Australian Schools Health and Fitness Survey was conducted on a representative sample of Australian schoolchildren aged 7 to 15 years. In children aged 9, 12, and 15, data on plasma cholesterol, triglycerides, and high-density lipoprotein cholesterol were obtained along with measurements of blood pressure, fitness, and body fatness. From an original sample of 2400 in these three age categories 1919 underwent the full set of measurements. Univariate analysis of these data revealed a strong association between body fatness and plasma lipids. There was no significant association between fitness (measured as physical work capacity at a heart rate of 170 beats per minute per kilogram of lean body mass) and plasma lipids, but a significant negative association was found for fitness and systolic blood pressure (r = -.12, P < .001). Multiple regression analysis revealed that the association of fitness with systolic blood pressure was only partly accounted for by the confounding effect of lower body fatness in fitter children.

CONCLUSIONS

These data collected on a representative sample of children under standardized conditions confirm a previous finding of a link between fitness and blood pressure in schoolchildren and also support a growing consensus that fitness is only weakly linked to plasma lipids and lipoproteins in children and adolescents.

Maternal smoking during pregnancy, growth, and bone mass in prepubertal children

There have been no studies of smoking during pregnancy and bone mineralization in children. The objective of this population-based longitudinal study was to determine whether maternal smoking during pregnancy is associated with bone mass and other growth variables in prepubertal children. We studied 330 8-year-old male and female children representing 47% of those who originally took part in a study of risk factors for Sudden Infant Death Syndrome in 1988. The main outcome measures were bone mineral density measured by a Hologic QDR2000 densitometer: birth weight, placental weight, height, and weight. Maternal smoking during pregnancy was associated with deficits in growth with these children having lower height (-1.53 cm, 95% confidence interval [CI] -3.03 to -0.03) and a trend to lower weight (-1.35 kg, 95% CI -2.75 to 0.11) at age 8. Furthermore, there was a disproportionate deficit in bone mass such that those children whose mothers smoked during pregnancy had lower size adjusted bone mass at the lumbar spine (-0.019 g/cm2, 95% CI -0.033 to -0.005) and femoral neck (-0.018 g/cm2, 95%CI -0.034 to -0.002) but not total body (-0.005 g/cm2, 95% CI -0.015 to 0.005). This association was only present for children born at term. Mothers who smoked during pregnancy also had lower placental weight (- 56 g, 95% CI -95 to -17), and further adjustment for placental weight led to nonsignificant results for smoking with both growth and bone parameters, suggesting that these associations may be mediated through placental size and function. Maternal smoking habit in 1996 was not significantly associated with bone mass at any site. In conclusion, this study has demonstrated a long-term negative association between maternal smoking during pregnancy and both growth and bone mass in children born at term, and suggests that the timing of exposure rather than the dose or duration is critical. If these associations are present in other populations and they persist until the attainment of peak bone mass, then our findings suggest that osteoporosis prevention programs should start very early in the life cycle.