Bich Tran - Academia.edu (original) (raw)
Papers by Bich Tran
The Journal of Clinical Endocrinology & Metabolism, 2014
Context and Objective: Suboptimal vitamin D status can be corrected by vitamin D supplementation,... more Context and Objective: Suboptimal vitamin D status can be corrected by vitamin D supplementation, but individual responses to supplementation vary. We aimed to examine genetic and nongenetic determinants of change in serum 25-hydroxyvitamin D (25(OH)D) after supplementation. Design and Participants: We used data from a pilot randomized controlled trial in which 644 adults aged 60 to 84 years were randomly assigned to monthly doses of placebo, 30 000 IU, or 60 000 IU vitamin D 3 for 12 months. Baseline characteristics were obtained from a self-administered questionnaire. Eighty-eight single-nucleotide polymorphisms (SNPs) in 41 candidate genes were genotyped using Sequenom MassArray technology. Serum 25(OH)D levels before and after the intervention were measured using the Diasorin Liaison platform immunoassay. We used linear regression models to examine associations between genetic and nongenetic factors and change in serum 25(OH)D levels. Results: Supplement dose and baseline 25(OH)D level explained 24% of the variability in response to supplementation. Body mass index, self-reported health status, and ambient UV radiation made a small additional contribution. SNPs in CYP2R1, IRF4, MC1R, CYP27B1, VDR, TYRP1, MCM6, and HERC2 were associated with change in 25(OH)D level, although only CYP2R1 was significant after adjustment for multiple testing. Models including SNPs explained a similar proportion of variability in response to supplementation as models that included personal and environmental factors. Conclusion: Stepwise regression analyses suggest that genetic variability may be associated with response to supplementation, perhaps suggesting that some people might need higher doses to reach optimal 25(OH)D levels or that there is variability in the physiologically normal level of 25(OH)D.
The Journal of Clinical Endocrinology & Metabolism, 2012
Context: The benefits of high serum levels of 25-hydroxyvitamin D [25(OH)D] are unclear. Trials a... more Context: The benefits of high serum levels of 25-hydroxyvitamin D [25(OH)D] are unclear. Trials are needed to establish an appropriate evidence base. Objective: We plan to conduct a large-scale trial of vitamin D supplementation for the reduction of cancer incidence and overall mortality and report here the methods and results of a pilot trial established to inform its design. Design: Pilot D-Health was a randomized trial carried out in a general community setting with 12 months intervention and follow-up. Participants: Participants were 60-to 84-yr-old residents of one of the four eastern Australian states who did not have any vitamin D-related disorders and who were not taking more than 400 IU supplementary vitamin D per day. A total of 644 participants were randomized, and 615 completed the study (two persons withdrew because of nonserious adverse events). Interventions: The interventions were monthly doses of placebo or 30,000 or 60,000 IU vitamin D 3. Main Outcomes: The main outcomes were the recruitment rate and changes in serum 25(OH)D. Results: Ten percent of those approached were recruited. At baseline, the mean 25(OH)D was 42 nmol/liter in all three study arms. The mean change in 25(OH)D in the placebo group was 0.12 nmol/liter, compared with changes of 22 and 36 nmol/liter in the 30,000-and 60,000-IU groups, respectively. Conclusions: The D-Health pilot has shown that a large trial is feasible in Australia and that a dose of 2000 IU/d will be needed to ensure that a large proportion of the population reaches the target serum 25(OH)D level.
European Journal of Cancer, 2014
Cigarette smoking is an established risk factor for pancreatic adenocarcinoma. However, few studi... more Cigarette smoking is an established risk factor for pancreatic adenocarcinoma. However, few studies have thoroughly investigated the effects of independent smoking dimensions (duration, intensity, cumulative dose and time since quitting) on risk estimates. We analysed data from the Queensland Pancreatic Cancer Study (QPCS), an Australian population-based case-control study, with the aim of determining which smoking component is primarily important to pancreatic cancer risk. Methods: Our study included 705 pancreatic cancer patients and 711 controls. Logistic regression and generalised additive logistic regression (for non-linear dose effects) were used to determine odds ratios (ORs) and 95% confidence intervals (CIs). Results: Compared to never-smokers, current smokers had an increased risk of pancreatic cancer (OR = 3.4; 95% CI 2.4-5.0) after adjustment for age, sex, education, alcohol intake and birth country. Of the various smoking dimensions, smoking duration and time since quitting had a greater effect on OR estimates (OR 1.3; 95% CI 1.1-1.4 and OR 0.8; 95% CI 0.7-0.8) than smoking intensity (OR 1.1; 95% CI 0.9-1.2), once ever-smoking was accounted for. Conclusions: This study confirms the association between cigarette smoking and pancreatic adenocarcinoma, and provides evidence to suggest that smoking pattern, in addition to dose effect, may affect disease risk.
Clinical Endocrinology, 2013
There has been a dramatic increase in vitamin D testing in Australia in recent years, prompting c... more There has been a dramatic increase in vitamin D testing in Australia in recent years, prompting calls for targeted testing. We sought to develop a model to identify people most at risk of vitamin D deficiency. This is a cross-sectional study of 644 60- to 84-year-old participants, 95% of whom were Caucasian, who took part in a pilot randomized controlled trial of vitamin D supplementation. Baseline 25(OH)D was measured using the Diasorin Liaison platform. Vitamin D insufficiency and deficiency were defined using 50 and 25 nmol/l as cut-points, respectively. A questionnaire was used to obtain information on demographic characteristics and lifestyle factors. We used multivariate logistic regression to predict low vitamin D and calculated the net benefit of using the model compared with 'test-all' and 'test-none' strategies. The mean serum 25(OH)D was 42 (SD 14) nmol/1. Seventy-five per cent of participants were vitamin D insufficient and 10% deficient. Serum 25(OH)D was positively correlated with time outdoors, physical activity, vitamin D intake and ambient UVR, and inversely correlated with age, BMI and poor self-reported health status. These predictors explained approximately 21% of the variance in serum 25(OH)D. The area under the ROC curve predicting vitamin D deficiency was 0·82. Net benefit for the prediction model was higher than that for the 'test-all' strategy at all probability thresholds and higher than the…
Cancer Prevention Research, 2012
Evidence is accumulating to suggest that higher exposure to solar ultraviolet radiation (UVR) is ... more Evidence is accumulating to suggest that higher exposure to solar ultraviolet radiation (UVR) is associated with decreased risk of internal cancers, but data for ovarian cancer are unclear. We aimed to examine the association between lifetime ambient UVR and ovarian cancer in a population-based-case–control study. The study included women aged 18 to 79 years with a new diagnosis of invasive (n = 1,215) or borderline (n = 285) epithelial ovarian cancer identified through a network of clinics and state cancer registries throughout Australia. Controls (n = 1,459), frequency matched to cases by age (5-year groups) and state of residence, were randomly selected from the National Electoral Roll. We asked participants to report where they had lived at different periods of their life and assigned an estimate of UVR using data from NASA's Total Ozone Mapping Spectrometer database (1997–2003). We estimated the association between ambient UVR and risk of ovarian cancer using conditional lo...
Cancer Epidemiology, 2013
To calculate pooled risk estimates of the association between pigmentary characteristics and basa... more To calculate pooled risk estimates of the association between pigmentary characteristics and basal cell carcinoma (BCC) of the skin. We searched three electronic databases and reviewed the reference lists of the retrieved articles until July 2012 to identify eligible epidemiologic studies. Eligible studies were those published in between 1965 and July 2012 that permitted quantitative assessment of the association between histologically-confirmed BCC and any of the following characteristics: hair colour, eye colour, skin colour, skin phototype, tanning and burning ability, and presence of freckling or melanocytic nevi. We included 29 studies from 2236 initially identified. We calculated summary odds ratios (ORs) using weighted averages of the log OR, using random effects models. We found strongest associations with red hair (OR 2.02; 95% CI: 1.68, 2.44), fair skin colour (OR 2.11; 95% CI: 1.56, 2.86), and having skin that burns and never tans (OR 2.03; 95% CI: 1.73, 2.38). All other factors had weaker but positive associations with BCC, with the exception of freckling of the face in adulthood which showed no association. Although most studies report risk estimates that are in the same direction, there is significant heterogeneity in the size of the estimates. The associations were quite modest and remarkably similar, with ORs between about 1.5 and 2.5 for the highest risk level for each factor. Given the public health impact of BCC, this meta-analysis will make a valuable contribution to our understanding of BCC.
The American Journal of Clinical Nutrition, 2013
Background: Observational data suggested that supplementation with vitamin D could reduce risk of... more Background: Observational data suggested that supplementation with vitamin D could reduce risk of infection, but trial data are inconsistent. Objective: We aimed to examine the effect of oral vitamin D supplementation on antibiotic use. Design: We conducted a post hoc analysis of data from pilot D-Health, which is a randomized trial carried out in a general community setting between October 2010 and February 2012. A total of 644 Australian residents aged 60-84 y were randomly assigned to receive monthly doses of a placebo (n = 214) or 30,000 (n = 215) or 60,000 (n = 215) IU oral cholecalciferol for #12 mo. Antibiotics prescribed during the intervention period were ascertained by linkage with pharmacy records through the national health insurance scheme (Medicare Australia). Results: People who were randomly assigned 60,000 IU cholecalciferol had nonsignificant 28% lower risk of having antibiotics prescribed at least once than did people in the placebo group (RR: 0.72; 95% CI: 0.48, 1.07). In analyses stratified by age, in subjects aged $70 y, there was a significant reduction in antibiotic use in the highdose vitamin D compared with placebo groups (RR: 0.53; 95% CI: 0.32, 0.90), whereas there was no effect in participants aged ,70 y (RR: 1.07; 95% CI: 0.58, 1.97) (P-interaction ¼ 0.1). Conclusion: Although this study was a post hoc analysis and statistically nonsignificant, this trial lends some support to the hypothesis that supplementation with 60,000 IU vitamin D/mo is associated with lower risk of infection, particularly in older adults. The trial was registered at the Australian New Zealand Clinical Trials Registry (anzctr.org.au) as ACTRN12609001063202.
The Journal of Clinical Endocrinology & Metabolism, 2014
Context and Objective: Suboptimal vitamin D status can be corrected by vitamin D supplementation,... more Context and Objective: Suboptimal vitamin D status can be corrected by vitamin D supplementation, but individual responses to supplementation vary. We aimed to examine genetic and nongenetic determinants of change in serum 25-hydroxyvitamin D (25(OH)D) after supplementation. Design and Participants: We used data from a pilot randomized controlled trial in which 644 adults aged 60 to 84 years were randomly assigned to monthly doses of placebo, 30 000 IU, or 60 000 IU vitamin D 3 for 12 months. Baseline characteristics were obtained from a self-administered questionnaire. Eighty-eight single-nucleotide polymorphisms (SNPs) in 41 candidate genes were genotyped using Sequenom MassArray technology. Serum 25(OH)D levels before and after the intervention were measured using the Diasorin Liaison platform immunoassay. We used linear regression models to examine associations between genetic and nongenetic factors and change in serum 25(OH)D levels. Results: Supplement dose and baseline 25(OH)D level explained 24% of the variability in response to supplementation. Body mass index, self-reported health status, and ambient UV radiation made a small additional contribution. SNPs in CYP2R1, IRF4, MC1R, CYP27B1, VDR, TYRP1, MCM6, and HERC2 were associated with change in 25(OH)D level, although only CYP2R1 was significant after adjustment for multiple testing. Models including SNPs explained a similar proportion of variability in response to supplementation as models that included personal and environmental factors. Conclusion: Stepwise regression analyses suggest that genetic variability may be associated with response to supplementation, perhaps suggesting that some people might need higher doses to reach optimal 25(OH)D levels or that there is variability in the physiologically normal level of 25(OH)D.
The Journal of Clinical Endocrinology & Metabolism, 2012
Context: The benefits of high serum levels of 25-hydroxyvitamin D [25(OH)D] are unclear. Trials a... more Context: The benefits of high serum levels of 25-hydroxyvitamin D [25(OH)D] are unclear. Trials are needed to establish an appropriate evidence base. Objective: We plan to conduct a large-scale trial of vitamin D supplementation for the reduction of cancer incidence and overall mortality and report here the methods and results of a pilot trial established to inform its design. Design: Pilot D-Health was a randomized trial carried out in a general community setting with 12 months intervention and follow-up. Participants: Participants were 60-to 84-yr-old residents of one of the four eastern Australian states who did not have any vitamin D-related disorders and who were not taking more than 400 IU supplementary vitamin D per day. A total of 644 participants were randomized, and 615 completed the study (two persons withdrew because of nonserious adverse events). Interventions: The interventions were monthly doses of placebo or 30,000 or 60,000 IU vitamin D 3. Main Outcomes: The main outcomes were the recruitment rate and changes in serum 25(OH)D. Results: Ten percent of those approached were recruited. At baseline, the mean 25(OH)D was 42 nmol/liter in all three study arms. The mean change in 25(OH)D in the placebo group was 0.12 nmol/liter, compared with changes of 22 and 36 nmol/liter in the 30,000-and 60,000-IU groups, respectively. Conclusions: The D-Health pilot has shown that a large trial is feasible in Australia and that a dose of 2000 IU/d will be needed to ensure that a large proportion of the population reaches the target serum 25(OH)D level.
European Journal of Cancer, 2014
Cigarette smoking is an established risk factor for pancreatic adenocarcinoma. However, few studi... more Cigarette smoking is an established risk factor for pancreatic adenocarcinoma. However, few studies have thoroughly investigated the effects of independent smoking dimensions (duration, intensity, cumulative dose and time since quitting) on risk estimates. We analysed data from the Queensland Pancreatic Cancer Study (QPCS), an Australian population-based case-control study, with the aim of determining which smoking component is primarily important to pancreatic cancer risk. Methods: Our study included 705 pancreatic cancer patients and 711 controls. Logistic regression and generalised additive logistic regression (for non-linear dose effects) were used to determine odds ratios (ORs) and 95% confidence intervals (CIs). Results: Compared to never-smokers, current smokers had an increased risk of pancreatic cancer (OR = 3.4; 95% CI 2.4-5.0) after adjustment for age, sex, education, alcohol intake and birth country. Of the various smoking dimensions, smoking duration and time since quitting had a greater effect on OR estimates (OR 1.3; 95% CI 1.1-1.4 and OR 0.8; 95% CI 0.7-0.8) than smoking intensity (OR 1.1; 95% CI 0.9-1.2), once ever-smoking was accounted for. Conclusions: This study confirms the association between cigarette smoking and pancreatic adenocarcinoma, and provides evidence to suggest that smoking pattern, in addition to dose effect, may affect disease risk.
Clinical Endocrinology, 2013
There has been a dramatic increase in vitamin D testing in Australia in recent years, prompting c... more There has been a dramatic increase in vitamin D testing in Australia in recent years, prompting calls for targeted testing. We sought to develop a model to identify people most at risk of vitamin D deficiency. This is a cross-sectional study of 644 60- to 84-year-old participants, 95% of whom were Caucasian, who took part in a pilot randomized controlled trial of vitamin D supplementation. Baseline 25(OH)D was measured using the Diasorin Liaison platform. Vitamin D insufficiency and deficiency were defined using 50 and 25 nmol/l as cut-points, respectively. A questionnaire was used to obtain information on demographic characteristics and lifestyle factors. We used multivariate logistic regression to predict low vitamin D and calculated the net benefit of using the model compared with 'test-all' and 'test-none' strategies. The mean serum 25(OH)D was 42 (SD 14) nmol/1. Seventy-five per cent of participants were vitamin D insufficient and 10% deficient. Serum 25(OH)D was positively correlated with time outdoors, physical activity, vitamin D intake and ambient UVR, and inversely correlated with age, BMI and poor self-reported health status. These predictors explained approximately 21% of the variance in serum 25(OH)D. The area under the ROC curve predicting vitamin D deficiency was 0·82. Net benefit for the prediction model was higher than that for the 'test-all' strategy at all probability thresholds and higher than the…
Cancer Prevention Research, 2012
Evidence is accumulating to suggest that higher exposure to solar ultraviolet radiation (UVR) is ... more Evidence is accumulating to suggest that higher exposure to solar ultraviolet radiation (UVR) is associated with decreased risk of internal cancers, but data for ovarian cancer are unclear. We aimed to examine the association between lifetime ambient UVR and ovarian cancer in a population-based-case–control study. The study included women aged 18 to 79 years with a new diagnosis of invasive (n = 1,215) or borderline (n = 285) epithelial ovarian cancer identified through a network of clinics and state cancer registries throughout Australia. Controls (n = 1,459), frequency matched to cases by age (5-year groups) and state of residence, were randomly selected from the National Electoral Roll. We asked participants to report where they had lived at different periods of their life and assigned an estimate of UVR using data from NASA's Total Ozone Mapping Spectrometer database (1997–2003). We estimated the association between ambient UVR and risk of ovarian cancer using conditional lo...
Cancer Epidemiology, 2013
To calculate pooled risk estimates of the association between pigmentary characteristics and basa... more To calculate pooled risk estimates of the association between pigmentary characteristics and basal cell carcinoma (BCC) of the skin. We searched three electronic databases and reviewed the reference lists of the retrieved articles until July 2012 to identify eligible epidemiologic studies. Eligible studies were those published in between 1965 and July 2012 that permitted quantitative assessment of the association between histologically-confirmed BCC and any of the following characteristics: hair colour, eye colour, skin colour, skin phototype, tanning and burning ability, and presence of freckling or melanocytic nevi. We included 29 studies from 2236 initially identified. We calculated summary odds ratios (ORs) using weighted averages of the log OR, using random effects models. We found strongest associations with red hair (OR 2.02; 95% CI: 1.68, 2.44), fair skin colour (OR 2.11; 95% CI: 1.56, 2.86), and having skin that burns and never tans (OR 2.03; 95% CI: 1.73, 2.38). All other factors had weaker but positive associations with BCC, with the exception of freckling of the face in adulthood which showed no association. Although most studies report risk estimates that are in the same direction, there is significant heterogeneity in the size of the estimates. The associations were quite modest and remarkably similar, with ORs between about 1.5 and 2.5 for the highest risk level for each factor. Given the public health impact of BCC, this meta-analysis will make a valuable contribution to our understanding of BCC.
The American Journal of Clinical Nutrition, 2013
Background: Observational data suggested that supplementation with vitamin D could reduce risk of... more Background: Observational data suggested that supplementation with vitamin D could reduce risk of infection, but trial data are inconsistent. Objective: We aimed to examine the effect of oral vitamin D supplementation on antibiotic use. Design: We conducted a post hoc analysis of data from pilot D-Health, which is a randomized trial carried out in a general community setting between October 2010 and February 2012. A total of 644 Australian residents aged 60-84 y were randomly assigned to receive monthly doses of a placebo (n = 214) or 30,000 (n = 215) or 60,000 (n = 215) IU oral cholecalciferol for #12 mo. Antibiotics prescribed during the intervention period were ascertained by linkage with pharmacy records through the national health insurance scheme (Medicare Australia). Results: People who were randomly assigned 60,000 IU cholecalciferol had nonsignificant 28% lower risk of having antibiotics prescribed at least once than did people in the placebo group (RR: 0.72; 95% CI: 0.48, 1.07). In analyses stratified by age, in subjects aged $70 y, there was a significant reduction in antibiotic use in the highdose vitamin D compared with placebo groups (RR: 0.53; 95% CI: 0.32, 0.90), whereas there was no effect in participants aged ,70 y (RR: 1.07; 95% CI: 0.58, 1.97) (P-interaction ¼ 0.1). Conclusion: Although this study was a post hoc analysis and statistically nonsignificant, this trial lends some support to the hypothesis that supplementation with 60,000 IU vitamin D/mo is associated with lower risk of infection, particularly in older adults. The trial was registered at the Australian New Zealand Clinical Trials Registry (anzctr.org.au) as ACTRN12609001063202.