Jennifer Cochrane

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.

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 infants 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.

Association of change in daily step count over five years with insulin sensitivity and adiposity: Population based cohort study

Objectives To investigate the association between change in daily step count and both adiposity and insulin sensitivity and the extent to which the association between change in daily step count and insulin sensitivity may be mediated by adiposity. Design Population based cohort study. Setting Tasmania, Australia. Participants 592 adults (men (n=267), mean age 51.4 (SD 12.2) years; women (n=325), mean age 50.3 (12.3) years) who participated in the Tasmanian component of the national AusDiab Study in 2000 and 2005. Main outcome measures Body mass index, waist to hip ratio, and HOMA insulin sensitivity at follow-up in 2005. Results Over the five year period, the daily step count decreased for 65% (n=382) of participants. Having a higher daily step count in 2005 than in 2000 was independently associated with lower body mass index (0.08 (95% confidence interval 0.04 to 0.12) lower per 1000 steps), lower waist to hip ratio (0.15 (0.07 to 0.23) lower), and greater insulin sensitivity (1.38 (0.14 to 2.63) HOMA units higher) in 2005. The mean increase in HOMA units fell to 0.34 (−0.79 to 1.47) after adjustment for body mass index in 2005. Conclusions Among community dwelling, middle aged adults, a higher daily step count at five year follow-up than at baseline was associated with better insulin sensitivity. This effect seems to be largely mediated through lower adiposity.

The relation between infant indoor environment and subsequent asthma.

Our aim was to examine the contribution of an infants indoor environment to childhood asthma using prospective data. We conducted a cross-sectional asthma survey in 1995 on 92% (6,378/6,911) of 7-year-olds in Tasmania, Australia. We linked these data with data collected in 1988 as part of the Tasmanian Infant Health Survey, which was designed to investigate sudden infant death. We were able to match 863 records out of the 1,111 in the 1988 survey and the 6,378 in the 1995 survey. The former group was interviewed at home at 1 month of age. In homes where at least one adult smoked in 1988, reported infant exposure to smoking in the same room in 1988 was associated with increased asthma by 1995 (relative risk = 1.52; 95% confidence interval = 1.01-2.29) after adjustment for confounders. The associations between infant exposure to environmental tobacco smoke and asthma were not consistent, however. Gas heater use in 1988 was associated with asthma (relative risk = 1.92; 95% confidence interval = 1.33-2.76). Markers of aeroallergen exposure at 1 month of age were not materially associated with asthma or wheeze. In some settings, air circulation practice with regard to bedroom door closure appeared important. Poor indoor air quality may play an important role in the development of childhood asthma.

Association between use of a quilt and sudden infant death syndrome : case-control study

The relation between an infants sleeping environment and development of the sudden infant death syndrome depends on the infants sleep position.1 We report how the association between the use of a quilt and the syndrome depends on sleep position. Between 1 October 1988 and 31 December 1995 in Tasmania 107 infants <1 year old died of the sudden infant death syndrome. Of the families affected, 100 (93%) participated in this study and were compared directly with 196 age matched controls. Methods are described elsewhere.1 A quilt is a coverlet made by stitching two thicknesses of fabric together with a filling (usually synthetic) enclosed between the layers. Conditional multiple logistic regression2 was used to evaluate interaction effects; egret 0.26.6 software (Cytel Software, Cambridge, MA, USA) provided matched odds ratios with logit-based 95% confidence intervals. An adverse effect of quilt use was evident in infants who did not sleep prone but not in infants who slept prone (1). This interaction was not altered by adjustment for sleeping on sheepskin; the interaction between sleeping on sheepskin and sleeping prone; mattress liner; mattress type; use of a quilt under the infant; use of a pillow; infant illness; heating …

Higher maternal dietary protein intake in late pregnancy is associated with a lower infant ponderal index at birth.

Aim:A high ponderal index at birth has been associated with later obesity and it has been suggested that intervention to prevent obesity and its sequela should consider the antenatal period. In this context, we investigated the association between maternal nutrition and birth anthropometry.Design:We analyzed data on 1040 mother–infant pairs collected during the Tasmanian Infant Health Survey (TIHS), Tasmania, 1988–1989. Maternal dietary intake during pregnancy was measured by food frequency questionnaire (FFQ) applied soon after birth. Outcomes of interest were birth weight, birth length, head circumference, ponderal index, head circumference –to-ponderal index ratio, placenta-to-birth weight ratio and head circumference-to-birth length index.Results:In multiple regression model, an increase of 10 g of absolute protein intake/day was associated with a reduction in birth weight of 17.8 g (95% CI: −32.7, −3.0; P=0.02). Protein intake was also associated negatively with ponderal index (β=−0.01; 95% CI: −0.02, −0.00; P=0.01). A 1 % increase in carbohydrate intake resulted in a 1% decline in placental weight relative to birth weight. Higher protein intake in the third trimester was associated with a reduced ponderal index among large birth weight infants but not low birth weight infants.Conclusions:This raises the possibility that any effect of high protein in altering infant anthropometry at birth may involve changes in body composition and future work to examine how a high-protein diet influences body composition at birth is warranted.

The association between maternal diet during pregnancy and bone mass of the children at age 16

Background/Objectives:Fetal life may be a critical period for the development and/or programming of metabolic systems, including the skeleton. However, it is unclear on the association between maternal nutrition during pregnancy and bone mass in their offspring at adolescence.Subjects/Methods:This was a birth cohort study of 216 adolescents (16.2±0.4 years). Dietary intake was measured by food frequency questionnaire. Bone densitometry was measured at the femoral neck, lumbar spine and total body by DXA.Results:After adjustment for confounders, bone mineral density (BMD) of the femoral neck was positively associated with magnesium density and negatively associated with fat density (all P-values <0.05). BMD of the lumbar spine was positively associated with calcium, magnesium and phosphorus density and negatively associated with fat density (all P-values <0.05). Maternal milk intake was significantly positively associated with lumbar spine BMD. After considering all significant nutrients in the same model, fat density remained significant negatively for the femoral neck and lumbar spine, whereas magnesium density remained significant positively for the femoral neck. No nutrient was significant for the total body.Conclusions:Maternal intake of milk, fat and magnesium during the third trimester of pregnancy is predictive of BMD at age 16, suggesting that in utero diet influences peak bone mass possibly through programming bone responses.

A prospective study of the association between home gas appliance use during infancy and subsequent dust mite sensitization and lung function in childhood

Background Home gas appliance use has been associated with child respiratory illness but prospective data on the relationship between infant exposure and the development of child allergic disease has not been readily available.

Parental smoking and infant respiratory infection: how important is not smoking in the same room with the baby?

OBJECTIVES We sought to quantify the effect of good smoking hygiene on infant risk of respiratory tract infection in the first 12 months of life. METHODS A cohort of 4486 infants in Tasmania, Australia, was followed from birth to 12 months of age for hospitalization with respiratory infection. Case ascertainment was 98.2%. RESULTS Relative to the infants of mothers who smoked postpartum but never in the same room with their infants, risk of hospitalization was 56% (95% confidence interval [CI] = 13%, 119%) higher if the mother smoked in the same room with the infant, 73% (95% CI = 18%, 157%) higher if the mother smoked when holding the infant, and 95% (95% CI = 28%, 298%) higher if the mother smoked while feeding the infant. CONCLUSIONS Parents who smoke should not smoke with their infants present in the same room.

Practical considerations when using pedometers to assess physical activity in population studies: lessons from the Burnie Take Heart Study.

Abstract The aim of this study was to summarize both practical and methodological issues in using pedometers to assess physical activity in a large epidemiologic study. As part of a population-based survey of cardiovascular disease risk factors, physical activity was assessed using pedometers and activity diaries in 775 men and women ages 25–64 years who were residents of Burnie, Tasmania, 1998–99. Common data problems were classified by type. The frequency of each problem and the methods used to identify it are reported along with strategies to correct or prevent each problem type. Pedometer data from 15 (1.9%) participants could not be used due to errors in completing the pedometer protocol. Among 760 participants with usable data, the median number of steps was 9,729 for men and 10,388 for women. Pedometer steps per day were modestly correlated (r = .20, p < .0001) with the duration of pedometer wear, which ranged from 4.50 to 21.75 hr. Adjustment for wear time, however, did not alter observed correlations between pedometer steps and cardiovascular risk factors. The authors conclude that pedometers can be used in large population studies with a relatively low frequency of data errors. However, guidelines for consistent data collection and interpretation are needed.