Gerarda Darlington

Risk factors for renal cell carcinoma: results of a population-based case-control study

For a case-control study of risk factors for renal cell carcinoma, a mailed questionnaire was used to collect data on 518 cases and 1,381 population-based controls in Ontario, Canada. Active cigarette smoking increased risk twofold among males (odds ratio estimate [OR]=2.0, 95 percent confidence interval (CI)=1.4–2.8) and females (OR=1.9, CI=1.3–2.6). Passive smoking appeared to increase risk somewhat among nonsmokers (males: OR=1.6, CI=0.5–4.7; females: OR=1.7, CI=0.8–3.4). A high Quetelet index (QI) was associated with a twofold increase in risk in both sexes, although this was based on reported weight at age 25 years for males (OR=1.9, CI=1.2–3.1) and five years prior to data collection for females (OR=2.5, CI=1.4–4.6). Diuretic use was associated with significantly increased risk among females, but not among males. Phenacetin use increased risk, while acetaminophen use was not associated with altered risk, although few subjects used either compound. Multiple urinary tract infections increased risk, but only significantly in females (OR=1.9, CI=1.2–2.9). Our data indicate the need for further exploration of passive smoking and diuretics as risk factors, as well as elucidation of mechanisms by which high lifetime QI and frequent urinary-tract infections might increase risk of this cancer.

Soy Protein Reduces Serum LDL Cholesterol and the LDL Cholesterol:HDL Cholesterol and Apolipoprotein B:Apolipoprotein A-I Ratios in Adults with Type 2 Diabetes

Type 2 diabetes is highly prevalent in North America and is associated with increased risk of cardiovascular disease (CVD). Evidence supports a role for soy protein in the reduction of serum lipids related to CVD risk; however, few studies have focused on adults with type 2 diabetes who are not on lipid-lowering medications and/or do not have diabetic complications. The purpose of this study was to determine the effect of soy protein isolate (SPI) consumption on serum lipids in adults with diet-controlled type 2 diabetes. Using a double-blind, randomized, crossover, placebo-controlled intervention study design, adults with diet-controlled type 2 diabetes (n = 29) consumed SPI (80 mg/d aglycone isoflavones) or milk protein isolate (MPI) for 57 d each separated by a 28-d washout period. Twenty-four-hour urine samples were collected on d 54-56 of each treatment for analysis of isoflavones and blood was collected on d 1 and 57 of each treatment and analyzed for serum lipids and apolipoproteins. SPI consumption increased urinary isoflavones compared with MPI. SPI consumption reduced serum LDL cholesterol (P = 0.04), LDL cholesterol:HDL cholesterol (P = 0.02), and apolipoprotein B:apolipoprotein A-I (P = 0.05) compared with MPI. SPI did not affect serum total cholesterol, HDL cholesterol, triacylglycerol, apolipoprotein B, or apolipoprotein A-I. These data demonstrate that consumption of soy protein can modulate some serum lipids in a direction beneficial for CVD risk in adults with type 2 diabetes.

Isoflavonoid content of Hong Kong soy foods.

Progress in understanding the effects of dietary soy isoflavones on chronic disease prevention in the Hong Kong Chinese population has been hampered by the lack of a comprehensive soy isoflavone database. In this study, we determined the concentrations and distribution of isoflavones in 47 foods included in a soy food frequency questionnaire by reverse-phase HPLC. Results indicated that most soy products contained isoflavones ranging from 1 mg of aglucon equivalents/100 g of wet weight (bean strip noodle and egg bean curd) to 80 mg of aglucon equivalents/100 g of wet weight (oyster sauce soybean and sweet bean curd sheet). Among our food groups, mean isoflavone concentrations were lowest in the soy milk group (9.99 mg of aglucon equivalents/100 g of wet weight) and highest in the bean curd skin group (40 mg of aglucon equivalents/100 g of wet weight). The conjugation patterns of isoflavones varied within and between food groups as influenced by the types of soybeans and the processing or cooking techniques used. The isoflavone concentrations reported herein will be useful for ascertaining the relationship between exposure to dietary soy isoflavones and health effects in the Chinese population.

Soya protein does not affect glycaemic control in adults with type 2 diabetes.

Evidence from observational, animal and human studies supports a role for soya protein and its isoflavones in the improvement of glycaemic control in type 2 diabetes. The objective of the present study was to determine the effect of isoflavone-rich soya protein on markers of glycaemic control in adults with type 2 diabetes. Using a randomised, crossover, double-blind, placebo-controlled design, adults with diet-controlled type 2 diabetes (n 29) consumed soya protein isolate (SPI) and milk protein isolate (MPI) for 57 d each separated by a 4-week washout. Blood was collected on days 1 and 57 of each treatment period for analysis of fasting HbA1C, and fasting and postprandial glucose, insulin and calculated indices of insulin sensitivity and resistance. Urine samples of 24 h were collected at the end of each treatment period for analysis of isoflavones. Urinary isoflavone excretion was significantly greater following consumption of SPI compared with MPI, and 20.7 % of the subjects (n 6) were classified as equol excretors. SPI consumption did not significantly affect fasting or postprandial glucose or insulin, fasting HbA1C, or indices of insulin sensitivity and resistance. These data do not support a role for soya protein in the improvement of glycaemic control in adults with diet-controlled type 2 diabetes and contribute to a limited literature of human studies on the effects of soya protein on the management of type 2 diabetes.

Parenting stress: a cross-sectional analysis of associations with childhood obesity, physical activity, and TV viewing

BackgroundParents influence their children’s obesity risk through feeding behaviours and modeling of weight-related behaviours. Little is known about how the general home environment, including parental stress, may influence children’s weight. The objective of this study was to explore the association between parenting stress and child body mass index (BMI) as well as obesity risk factors, physical activity and television (TV) viewing.MethodsWe used cross-sectional data from 110 parent–child dyads participating in a community-based parenting intervention. Child heights and weights were measured by trained research assistants. Parents (93% mothers) reported level of parenting stress via the Parenting Stress Index- Short Form (PSI-3-SF) as well as children’s activity behaviours and TV viewing. This was an ethnically diverse (55% Hispanic/Latino, 22% Black), low-income (64% earning < 

Dietary supplement use in the spinal cord injury population

45,000/year) sample.ResultsLevel of parenting stress was not associated with children’s risk of being overweight/obese. Children with highly stressed parents were less likely to meet physical activity guidelines on weekdays than children with normally stressed parents (OR = 0.33, 95% CI, 0.12-0.95). Parents experiencing high stress were less likely to set limits on the amount of TV their children watched (OR = 0.32, 95% CI, 0.11, 0.93).ConclusionResults suggest stress specific to parenting may not be associated with increased obesity risk among children. However, future interventions may need to address stress as a possible underlying factor associated with unhealthful behaviours among preschoolers.

Meta-analysis of community-based cluster randomization trials with binary outcomes.

Study design:Longitudinal, non-experimental.Objectives:To determine the following: (1) prevalence of supplement use in a representative sample of the chronic spinal cord injury (SCI) population; (2) most frequently consumed supplements; and (3) characteristics of consistent supplement users.Setting:Ontario, Canada.Methods:A structured questionnaire was used to collect demographic information from 77 community-dwelling adults with chronic SCI (50.6% paraplegia, 81.8% male, 42.4±11.9 years, body mass index (BMI) 25.4±5.1 kg m−2). A standardized form was used to record dietary intake, including supplements, in the previous 24 h, at three time points (baseline, 6 months and 18 months). Logistic regression and multivariate logistic regression were used to determine which characteristic(s) was (were) associated with consistent supplement use.Results:Seventy-one percent of the sample reported using supplements at least once, with 50.6% being classified as consistent supplement users (at least twice across the three time points). The top three supplements consumed were multivitamins (25%), calcium (20%) and vitamin D (16%). Supplement use status was not associated with gender, level of injury, age, education, physical activity, BMI, smoking or alcohol intake.Conclusions:Dietary supplement use was common in our sample of individuals with long-standing SCI, but no common characteristics distinguished users from non-users. We suggest that health practitioners be aware of the high dietary supplement use in this population so that they can probe for type, dose and frequency, as supplements may have an important influence on dietary assessment results.

Multi-state models for investigating possible stages leading to bipolar disorder

Background Cluster randomization trials are widely used to test the effect of an intervention when individuals are naturally found in groups such as communities. For several separate studies of a similar intervention, it may be of interest to combine their results using meta-analysis procedures. However, this task requires consideration of both the likely dependencies among cluster members (intracluster correlation) and stratification based on the studies considered. Purpose In this article, several possible approaches for meta-analysis are considered for cluster randomization trials having a binary outcome. Methods It is first noted that the standard Mantel—Haenszel test is invalid in this context since it ignores dependencies among cluster members. Two modifications are therefore considered as well as a general inverse variance approach and a procedure based on the Woolf statistic which does not require the availability of trial-specific design effects. Empirical Type I errors and powers for the different procedures considered are evaluated using Monte Carlo simulation. To illustrate the techniques, data are used from trials performed in four countries to compare two antenatal care programs with respect to their effects on the risk of hypertension during pregnancy. Results For the simulation scenarios considered, an adjusted Mantel—Haenszel procedure provides a valid test with the greatest power slightly outperforming the general inverse variance approach. Limitations The potential need to adjust for possible confounding was not considered. However, more detailed information on confounders would not likely be available for most meta-analyses. Conclusion Two procedures performed well. However, the choice of analysis approach also inevitably depends on the nature and extent of the available data. Clinical Trials 2007; 4: 491—498. http://ctj.sagepub.com

Event‐weighted proportional hazards modelling for recurrent gap time data

BackgroundIt has been proposed that bipolar disorder onsets in a predictable progressive sequence of clinical stages. However, there is some debate in regard to a statistical approach to test this hypothesis. The objective of this paper is to investigate two different analysis strategies to determine the best suited model to assess the longitudinal progression of clinical stages in the development of bipolar disorder.MethodsData previously collected on 229 subjects at high risk of developing bipolar disorder were used for the statistical analysis. We investigate two statistical approaches for analyzing the relationship between the proposed stages of bipolar disorder: 1) the early stages are considered as time-varying covariates affecting the hazard of bipolar disorder in a Cox proportional hazards model, 2) the early stages are explicitly modelled as states in a non-parametric multi-state model.ResultsWe found from the Cox model thatthere was evidence that the hazard of bipolar disorder is increased by the onset of major depressive disorder. From the multi-state model, in high-risk offspring the probability of bipolar disorder by age 29 was estimated as 0.2321. Cumulative incidence functions representing the probability of bipolar disorder given major depressive disorder at or before age 18 were estimated using both approaches and found to be similar.ConclusionsBoth the Cox model and multi-state model are useful approaches to the modelling of antecedent risk syndromes. They lead to similar cumulative incidence functions but otherwise each method offers a different advantage.

A competing risks model for correlated data based on the subdistribution hazard

The analysis of gap times in recurrent events requires an adjustment to standard marginal models. One can perform this adjustment with a modified within-cluster resampling technique; however, this method is computationally intensive. In this paper, we describe a simple adjustment to the standard Cox proportional hazards model analysis that mimics the intent of within-cluster resampling and results in similar parameter estimates. This method essentially weights the partial likelihood contributions by the inverse of the number of gap times observed within the individual while assuming a working independence correlation matrix. We provide an example involving recurrent mammary tumours in female rats to illustrate the methods considered in this paper.