Angela Pezic

Variation in Associations between Allelic Variants of the Vitamin D Receptor Gene and Onset of Type 1 Diabetes Mellitus by Ambient Winter Ultraviolet Radiation Levels: A Meta-Regression Analysis

Vitamin D receptor (VDR) gene polymorphisms may be associated with risk of developing type 1 diabetes mellitus (T1DM), but reports have been conflicting. The authors reexamined population-based case-control studies on selected VDR polymorphisms and T1DM to investigate whether variation in reported associations could be partly explained by differences in ambient winter ultraviolet radiation (UVR) levels. A meta-analysis of 16 studies from 19 regions (midwinter UVR range, 1.0-133.8 mW/m(2)) was conducted. The association between winter UVR and the log odds ratio was examined by meta-regression. For FokI and BsmI, the log odds ratio for the association between the F and B alleles and T1DM increased as regional winter UVR increased (p = 0.039 and p = 0.036, respectively). The association between the TaqI T allele and T1DM was reduced with increasing winter UVR (p = 0.040). Low winter regional UVR was associated with a higher proportion of controls carrying BsmI and ApaI uppercase alleles and a lower proportion of controls carrying TaqI uppercase alleles. These findings strengthen the case that VDR variants are involved in the etiology of T1DM. They suggest that environmental UVR may influence the association between VDR genotype and T1DM risk. Further work on VDR polymorphisms and T1DM should concomitantly examine the roles of past UVR exposure and vitamin D status.

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.

Objectively measured daily steps and subsequent long term all-cause mortality: The Tasped Prospective Cohort Study

Background Self–reported physical activity has been inversely associated with mortality but the effect of objectively measured step activity on mortality has never been evaluated. The objective is to determine the prospective association of daily step activity on mortality among free-living adults. Methods and Findings Cohort study of free-living adults residing in Tasmania, Australia between 2000 and 2005 who participated in one of three cohort studies (n = 2 576 total participants). Daily step activity by pedometer at baseline at a mean of 58.8 years of age, and for a subset, repeated monitoring was available 3.7 (SD 1.3) years later (n = 1 679). All-cause mortality (n = 219 deaths) was ascertained by record-linkage to the Australian National Death Index; 90% of participants were followed-up over ten years, until June 2011. Higher daily step count at baseline was linearly associated with lower all-cause mortality (adjusted hazard ratio AHR, 0.94; 95% CI, 0.90 to 0.98 per 1 000 steps; P = 0.004). Risk was altered little by removing deaths occurring in the first two years. Increasing baseline daily steps from sedentary to 10 000 steps a day was associated with a 46% (95% CI, 18% to 65%; P = 0.004) lower risk of mortality in the decade of follow-up. In addition, those who increased their daily steps over the monitoring period had a substantial reduction in mortality risk, after adjusting for baseline daily step count (AHR, 0.39; 95% CI, 0.22 to 0.72; P = 0.002), or other factors (AHR, 0.38; 95% CI, 0.21–0.70; P = 0.002). Conclusions Higher daily step count was linearly associated with subsequent long term mortality among free living adults. These data are the first to quantify mortality reductions using an objective measure of physical activity in a free living population. They strongly underscore the importance of physical inactivity as a major public health problem.

Association between early-life factors and risk of child-onset Crohn's disease among Victorian children born 1983-1998: a birth cohort study.

Background: The incidence of Crohns disease (CD) with onset before age 16 has increased. Several perinatal characteristics have been associated with CD. Our objective was to examine the temporal change in CD incidence by period of birth and the extent that this could be attributed to perinatal characteristics associated with higher CD risk. Methods: A record linkage study was conducted utilizing the perinatal records of Victorian births 1983–1998 inclusive and a state‐based CD registry. Proportional hazards models were used to investigate the perinatal factors in relation to the onset of CD by age 16. Further, a nested case control study was conducted to examine the association between sibling exposure and CD risk. Results: The CD incidence rate for births 1983–1998 was 2.01 (95% confidence interval [CI] 1.79, 2.27) per 100,000 child‐years. A birth cohort effect was demonstrated, with higher CD risk for 1992–1998 versus 1983–1991 births (hazard ratio [HR] 1.56; 95% CI 1.18, 2.06). Perinatal characteristics associated with higher CD risk included urban location, higher socioeconomic status, married mother, a congenital abnormality and delivery by elective cesarean section. Sibling exposure during the first 6 years of life was not associated with CD risk. The increased CD incidence among more recent births was not accounted for by changes in these measured perinatal factors. Conclusions: The temporal increase in CD incidence documented for births up to 1990 has continued for children born after 1991 and was not accounted for by temporal changes in the measured perinatal factors.

Effects of school-based interventions for direct delivery of physical activity on fitness and cardiometabolic markers in children and adolescents: a systematic review of randomized controlled trials.

To evaluate the effectiveness of school‐based physical activity interventions on fitness, adiposity and cardiometabolic outcomes among schoolchildren. Medline, Embase, EBSCOhost CINAHL and ERIC databases were searched up to October 2012. Inclusion criteria: intervention delivered at school with controls having no intervention or usual physical education classes; participants aged 5–18 years; outcomes spanning some or all of the above. We assessed levels of evidence for identified trials based on methodological quality and sample size. Dose of the interventions (a total summary measure of intensity, frequency and duration) were considered. Eighteen randomized controlled trials (RCTs, total participants = 6,207) were included, of which six were large, higher quality trials with high dose of the intervention. The intervention was consistent in increasing fitness with large, higher quality studies and high dose of intervention providing strong evidence. Dose of school‐based physical activity is an important determinant of trial efficiency. Some large, higher quality RCTs provided strong evidence for interventions to decrease skin‐fold thickness, increase fitness and high‐density lipoprotein cholesterol. Evidence for body mass index, body fat and waist circumference, blood pressure and triglycerides, low‐density lipoprotein cholesterol and total cholesterol remain inconclusive and require additional higher quality studies with high dose of interventions to provide conclusive evidence.

A temporal decline in asthma but not eczema prevalence from 2000 to 2005 at school entry in the Australian Capital Territory with further consideration of country of birth

BACKGROUND Asthma prevalence has declined in some countries over the past 10 years. Most reports have been based on population surveys conducted at two points of time in a given location. Comparisons across countries and time periods can be limited by differences in study methodology or disease diagnostics in different communities. Here, we examined trends in asthma prevalence using serial annual data and further examine the importance of country of birth. METHODS The source population has children aged 4-6 commencing school in the Australian Capital Territory from 2000 to 2005 inclusive. Over 80% of these children and their families completed a health questionnaire on asthma, other atopic disease and respiratory symptoms using some questions from the International Study of Asthma and Allergies in Childhood (n = 22 882). Current asthma has been previously validated against physician assessment in this setting. RESULTS The prevalence of current asthma declined (P < 0.001) but eczema ever increased (P < 0.001) from 2000 to 2005. The asthma decline was predominantly linear in form, and accompanied by a reduction in night cough and shortness of breath but not recent wheeze. Compared with Australian-born children, children from New Zealand and the United Kingdom had a similar prevalence of asthma, hay fever and eczema history. However, children born in other countries, such as Asia, generally had a lower prevalence of these disorders. The temporal trends for atopic disorders or respiratory symptoms did not differ for overseas-born compared with Australian-born children. CONCLUSION The decline in current asthma prevalence from 2000 to 2005 was linear in form and appeared uncoupled from trends in child eczema. Country of birth was associated with marked variation in atopic disorder prevalence. The similar temporal trends for Australian vs overseas-born children indicate that the factors underlying the asthma prevalence decline are unlikely to be only in the pre-natal period.

Maternal and infant factors associated with neonatal adiposity: results from the Tasmanian Infant Health Survey (TIHS).

Objective:To examine the maternal and neonatal factors associated with offspring adiposity and the role of birth and placental weight as potential mediators in such associations.Design:The Tasmanian Infant Health Survey was a prospective cohort study conducted between 1988 and 1995 in Australia to investigate the cause of Sudden Infant Death Syndrome. This large infant cohort provides measurement of skinfolds on 7945 mothers and their offspring.Subjects:Participants included singletons born ⩾37 weeks gestation who were at high risk of sudden infant death syndrome identified through a composite score that included birth weight, maternal age, neonatal gender, season of birth, duration of second-stage labor and intention to breastfeed.Measurements:Neonatal adiposity was assessed from skinfold measurements of the subscapular (SSF) and triceps folds (TSF) taken at birth. Maternal early-pregnancy body mass index (BMI) was calculated from self-reported height and weight. Neonatal data were extracted from birth records. Data relating to other environmental exposures were obtained from questionnaires administered when neonates were ∼4-days old.Results:In multivariable models, higher maternal adiposity, increasing maternal age, gestation age, delivery by Caesarian section and female gender were associated with larger SSF independent of placental and birth weight (P<0.001). Maternal age and delivery by Caesarian section were significantly associated with larger TSF, whereas gestational age and male gender were associated with thinner TSF independent of placental and birth weight. Higher early-pregnancy BMI, maternal weight gain, maternal age, parity and gestational age were significantly associated with larger placental and birth weight. Smoking during pregnancy was associated with smaller birth weight but not with placental weight.Conclusion:In addition to birth weight, maternal adiposity and placental weight were important additional factors associated with neonatal adiposity.

CLARITY – ChiLdhood Arthritis Risk factor Identification sTudY

BackgroundThe aetiology of juvenile idiopathic arthritis (JIA) is largely unknown. We have established a JIA biobank in Melbourne, Australia called CLARITY – C hiL dhood A rthritis R isk factor I dentification sT udY, with the broad aim of identifying genomic and environmental disease risk factors. We present here study protocols, and a comparison of socio-demographic, pregnancy, birth and early life characteristics of cases and controls collected over the first 3 years of the study.MethodsCases are children aged ≤18 years with a diagnosis of JIA by 16 years. Controls are healthy children aged ≤18 years, born in the state of Victoria, undergoing a minor elective surgical procedure. Participant families provide clinical, epidemiological and environmental data via questionnaire, and a blood sample is collected.ResultsClinical characteristics of cases (n = 262) are similar to those previously reported. Demographically, cases were from families of higher socio-economic status. After taking this into account, the residual pregnancy and perinatal profiles of cases were similar to control children. No case-control differences in breastfeeding commencement or duration were detected, nor was there evidence of increased case exposure to tobacco smoke in utero. At interview, cases were less likely to be exposed to active parental smoking, but disease-related changes to parent behaviour may partly underlie this.ConclusionsWe show that, after taking into account socio-economic status, CLARITY cases and controls are well matched on basic epidemiological characteristics. CLARITY represents a new study platform with which to generate new knowledge as to the environmental and biological risk factors for JIA.

Objectively Measured Physical Activity and the Subsequent Risk of Incident Dysglycemia: The Australian Diabetes, Obesity and Lifestyle Study (AusDiab)

OBJECTIVE To investigate pedometer-measured physical activity (PA) in 2000 and change in PA over 5 years with subsequent risk of dysglycemia by 2005. RESEARCH DESIGN AND METHODS This prospective cohort study in Tasmania, Australia, analyzed 458 adults with normal glucose tolerance and a mean (SD) age of 49.7 (12.1) years in 2000. Variables assessed in 2000 and 2005 included PA, by pedometer and questionnaire, nutrient intake, and other lifestyle factors. Incident dysglycemia was defined as the development of impaired fasting glucose or impaired glucose tolerance revealed by oral glucose tolerance testing in 2005, without type 2 diabetes. RESULTS Incident dysglycemia developed in 26 participants during the 5-year period. Higher daily steps in 2000 were independently associated with a lower 5-year risk of incident dysglycemia (adjusted odds ratio [AOR] 0.87 [95% CI 0.77–0.97] per 1,000-step increment). Higher daily steps in 2005, after controlling for baseline steps in 2000 (thus reflecting change in steps over 5 years), were not associated with incident dysglycemia (AOR 1.02 [0.92–1.14]). Higher daily steps in 2000 were also associated with lower fasting blood glucose, but not 2-h plasma glucose by 2005. Further adjustment for BMI or waist circumference did not remove these associations. CONCLUSIONS Among community-dwelling adults, a higher rate of daily steps is associated with a reduced risk of incident dysglycemia. This effect appears to be not fully mediated through reduced adiposity.

Maternal antenatal peanut consumption and peanut and rye sensitization in the offspring at adolescence

Cite this as: A. S. Kemp, A‐L Ponsonby,T. Dwyer J. A. Cochrane, A. Pezic and G. Jones, Clinical & Experimental Allergy, 2011 (41) 224–231.