Biomedical subjects

Will D King

Publications and source records attributed to Will D King.

11 recordsLinked to original sources

PubMed2006

Total and specific fluid consumption as determinants of bladder cancer risk.

We pooled the data from 6 case-control studies of bladder cancer with detailed information on fluid intake and water pollutants, particularly trihalomethanes (THM), and evaluated the bladder cancer risk associated with total and specific fluid consumption. The analysis included 2,729 cases and 5,150 controls. Odds ratios (OR) and 95% confidence intervals (CI) for fluid consumption were adjusted for age, gender, study, smoking status, occupation and education. Total fluid intake was associated with an increased risk of bladder cancer in men. The adjusted OR for 1 l/day increase in intake was 1.08, (95% CI 1.03-1.14, p-value for linear trend <0.001), while no trend was observed in women (OR=1.04, 0.94-1.15; p-value=0.7). OR was 1.33 (1.12-1.58) for men in the highest category of intake (>3.5 l/day) as compared to those in the lowest ( 2 l/day vs. 5 cups of coffee daily vs. <5 and for THM exposure, but neither exposure confounded or modified the OR for tap water intake. The association of bladder cancer with tap water consumption, but not with nontap water fluids, suggests that carcinogenic chemicals in tap water may explain the increased risk.

Age Factors↗

PubMed2006

Stillbirth risk factors according to timing of exposure.

PURPOSE: The purpose of the present study is to identify risk factors for stillbirth and explore hypotheses about the cause of stillbirth based on the time in gestation when exposures occur. METHODS: Relationships between lifestyle factors, pregnancy conditions, medication use, and occupation on risk for stillbirth were examined within a population-based case-control study. Women who had a stillbirth and a random sample of women who had a live birth between 1999 and 2001 were identified through perinatal databases in Nova Scotia and Eastern Ontario, Canada. Exposure data were collected for each month of pregnancy and analyzed within trimesters. Case-control data were converted to case-cohort data, and hazard ratios (HRs) and 95% confidence intervals (CIs) were determined from Cox proportional hazards models. RESULTS: This study included 105 stillbirth cases and 389 live-birth controls. Fertility treatment in the present pregnancy was associated with increased risk for stillbirth (adjusted HR, 4.0; 95% CI, 1.4-11.6). Smoking during the first trimester also was associated with increased risk for stillbirth (adjusted HR, 2.4; 95% CI, 1.2-4.9). Other risk factors included antiemetic use during the first trimester, second-trimester antibiotic use, low family income, and age older than 35 years. CONCLUSIONS: Risk factors identified in this study concur with findings of previous studies and support the importance of early pregnancy exposures on stillbirth risk.

Adult↗

PubMed2006

A pooled analysis of bladder cancer case-control studies evaluating smoking in men and women.

OBJECTIVE: A recent study suggested that risk of bladder cancer may be higher in women than in men who smoked comparable amounts of cigarettes. We pooled primary data from 14 case-control studies of bladder cancer from Europe and North America and evaluated differences in risk of smoking by gender. METHODS: The pooled analysis included 8316 cases (21% women) and 17,406 controls (28% women) aged 30-79 years. Odds ratios (ORs) and 95% confidence intervals (95% CI) for smoking were adjusted for age and study. Exposure-response was evaluated in a stratified analysis by gender and by generalized additive models. RESULTS: The odds ratios for current smokers compared to nonsmokers were 3.9 (95% CI 3.5-4.3) for males and 3.6 (3.1-4.1) for females. In 11 out of 14 studies, ORs were slightly higher in men. ORs for current smoking were similar for men (OR = 3.4) and women (OR = 3.7) in North America, while in Europe men (OR = 5.3) had higher ORs than women (OR = 3.9). ORs increased with duration and intensity in both genders and the exposure-response patterns were remarkably similar between genders. CONCLUSION: These results do not support the hypothesis that women have a higher relative risk of smoking-related bladder cancer than men.

Adult↗

PubMed2004

Exposure assessment in epidemiologic studies of adverse pregnancy outcomes and disinfection byproducts.

A major challenge in studies that examine the association between disinfection byproducts in drinking water and pregnancy outcomes is the accurate representation of a subject's exposure. We used household water samples and questionnaire information on water-use behavior to examine several aspects of exposure assessment: (i) the distribution and correlation of specific disinfection byproducts, (ii) spatial distribution system and temporal variation in byproduct levels, and (iii) the contribution of individual water-use behavior. The level of specific trihalomethanes (THMs) and haloacetic acids (HAAs) was determined for 360 household water samples in Eastern Ontario and Nova Scotia. Subjects were interviewed regarding tap water ingestion and showering and bathing practices. In both provinces, total THMs correlated highly with chloroform (correlation coefficient (r) >0.95) and less so with total HAAs (r = 0.74 in Nova Scotia and r = 0.52 in Ontario). The correlation between total THMs and bromodichloromethane was high in Nova Scotia (r = 0.63), but low in Ontario (r = 0.26). The correlation was between THM level in individual household samples, and the mean THM level during the same time period from several distribution system samples was 0.63, while a higher correlation in THM level was observed for samples taken at the same location 1 year apart (r = 0.87). A correlation of 0.73 was found between household THM level and a total exposure measure incorporating ingestion, showering, and bathing behaviors. These results point to the importance of: measurement of different classes of byproducts; household rather than distribution system sampling; and, incorporation of subject behaviors in exposure assessment in epidemiologic studies of disinfection byproducts and adverse pregnancy outcomes.

Acetates↗

PubMed2004

Disinfection byproducts and bladder cancer: a pooled analysis.

BACKGROUND: Exposure to disinfection byproducts in drinking water has been associated with an increased risk of bladder cancer. We pooled the primary data from 6 case-control studies of bladder cancer that used trihalomethanes as a marker of disinfection byproducts. METHODS: Two studies were included from the United States and one each from Canada, France, Italy, and Finland. Inclusion criteria were availability of detailed data on trihalomethane exposure and individual water consumption. The analysis included 2806 cases and 5254 controls, all of whom had measures of known exposure for at least 70% of the exposure window of 40 years before the interview. Cumulative exposure to trihalomethanes was estimated by combining individual year-by-year average trihalomethane level and daily tap water consumption. RESULTS: There was an adjusted odds ratio (OR) of 1.24 in men exposed to an average of more than 1 microg/L (ppb) trihalomethanes compared with those who had lower or no exposure (95% confidence interval [CI] = 1.09-1.41). Estimated relative risks increased with increasing exposure, with an OR of 1.44 (1.20-1.73) for exposure higher than 50 microg/L (ppb). Similar results were found with other indices of trihalomethane exposure. Among women, trihalomethane exposure was not associated with bladder cancer risk (0.95; 0.76-1.20). CONCLUSIONS: These findings strengthen the hypothesis that the risk of bladder cancer is increased with long-term exposure to disinfection byproducts at levels currently observed in many industrialized countries.

Age Distribution↗

PubMed2004

Residential mobility during pregnancy.

In epidemiological studies of environmental exposures and adverse pregnancy outcomes, maternal residence at delivery is often used to assign an exposure level, based on routinely collected data. In order to examine the potential for exposure misclassification due to residential mobility, we examined maternal mobility according to changes in residence overall, as well as changes in municipality and county. The potential for mobility to be related to pregnancy outcomes was considered by examining the relationship between mobility and risk factors commonly included in investigations of adverse pregnancy outcomes. Previously collected data were studied from 398 population-based control subjects from a case-control study of stillbirths. We compared demographic, lifestyle, medical, pregnancy and environmental factors of women who moved during pregnancy with those who did not. Bivariable and multivariable log binomial regressions were used to identify risk factors that were associated with mobility during pregnancy. Twelve per cent of subjects moved at least once during their pregnancy. Among women who moved, the majority (62%) moved within the same municipality. In bivariable analyses, we found that low family income, lower maternal age, unmarried status and tobacco use were associated with an increased likelihood of moving during pregnancy, whereas women who used folic acid before conception and who had a higher prepregnancy body mass index (BMI) were less likely to move during pregnancy. In multivariable analyses, only family income, age and prepregnancy BMI were independently predictive of mobility. These results indicate that in studies using maternal residence at delivery to assign environmental exposures, mobility during pregnancy is likely to be prevalent enough to introduce exposure misclassification. The potential for differential exposure misclassification should be considered should any of the risk factors for moving identified by this study also be risk factors for the outcome under study.

Adult↗

PubMed2004

The occurrence of abruptio placentae in Canada: 1990 to 1997.

Abruptio placentae is a serious obstetric condition associated with an increased incidence of perinatal mortality and morbidity. Despite this, there is little information on the occurrence of abruptio placentae in Canada. The Discharge Abstract Database from the Canadian Institute for Health Information was used to identify a cohort of women who had singleton live or stillbirth deliveries in Canada between 1990 and 1997 (n = 2,162,815). Rates of abruptio placentae and abruptio placentae ending in stillbirth were examined by calendar year, province, maternal age and urban/rural status. There is a trend towards an increasing rate of abruptio placentae by year, from 10.9 (95 % confidence interval [CI] 10.5-11.3) cases/1000 deliveries in 1990 to a high of 12.1 (95% CI 11.6-12.5) cases/1000 deliveries in 1996, while the rate ending in stillbirth remained relatively constant. The abruptio placentae rate was highest in mothers over 40 years of age and the case-fatality rate highest in those under 20. These results provide a baseline reference for rates of abruptio placentae in Canada.

Abruptio Placentae↗

PubMed2003

A cluster randomized trial of a sex education programme in Belize, Central America.

BACKGROUND: Concerns about adverse consequences of early childbearing and risk of sexually transmitted diseases (STD) have renewed interest in the sexual behaviour of adolescents in developing countries, where they represent a large proportion of the population and are at highest risk. To date, little is known about the sexual knowledge of adolescents in developing countries. This study's primary objective was to evaluate the effectiveness of a responsible sexuality education programme (RSP) in changing knowledge associated with sex and sexuality; secondary objectives were to evaluate changes in attitudes and behavioural intent. METHODS: A cluster randomized design randomizing high school classes in Belize City. Subjects were 13-19 years old. RESULTS: Seven schools in Belize City were selected; 8 classrooms were randomized to the intervention arm and 11 classrooms to the control arm (N = 399). The intervention was associated with two more correct answers on the post-test (difference score was 2.22 points, 95% CI = 0.53, 3.91) after adjusting for gender and previous sexual experience. After controlling for gender and previous sexual experience, the intervention was associated with no change in the attitudes (0.06, 95% CI: -2.89, 2.82) or behavioural intent domains (0.84, 95% CI: -1.12, 2.46). CONCLUSIONS: Greater changes in knowledge were observed in the intervention group than in the control group following the intervention. Changes were not observed for the attitude or behavioural intent domains. These results and the results of similar studies may be used to further improve sex education programmes as it is imperative that students have access to the information necessary to make informed decisions regarding their sexual health.

Acquired Immunodeficiency Syndrome↗

PubMed2003

Dietary predictors of concentrations of polychlorinated biphenyls in breast adipose tissue of women living in Ontario, Canada.

The authors evaluated dietary predictors of concentrations of 11 polychlorinated biphenyls (PCBs) in breast adipose tissue from 190 women with benign breast disease who live in Ontario, Canada. Consumption of fish was positively correlated with, and the most consistent dietary predictor of, breast tissue PCB levels. Dietary predictors accounted for < 8% of the variation in breast adipose tissue PCB levels. Age was positively and most strongly associated with tissue PCB levels, perhaps representing long-term dietary intake and the complex interplay of absorption, metabolism, distribution, and excretion.

Adipose Tissue↗

PubMed2003

Markers of loss of control of hypertension.

OBJECTIVE: To identify markers for loss of control of hypertension. DESIGN: Questionnaire administered to patients who had been monitored for 18 months and had had their blood pressure (BP) measured many times. SETTING: Fifty family practices in southeastern Ontario. PARTICIPANTS: Three hundred eighty-five adults with essential hypertension that was initially stable and controlled by medication. MAIN OUTCOME MEASURES: Change in BP (from baseline to mean of three measurements over 18 months) and proportion of patients with BP exceeding threshold values at most follow-up visits. RESULTS: Higher income was associated with an increase in diastolic BP; poor adherence to medication regimens and higher life stress were associated with increases in systolic BP Stress also led to a twofold increase in risk of exceeding BP thresholds. Other factors under study were not related to loss of control. CONCLUSION: Adherence to medication regimens, higher income, and life stress were the only factors associated with elevated BP or loss of control in previously controlled hypertension.

Antihypertensive Agents↗

PubMed2003

Lack of association between activity or fitness and loss of control of hypertension.

BACKGROUND: Many treated hypertensive patients have inadequate control of their blood pressure. Physical activity and cardiorespiratory fitness are important in the development and treatment of hypertension. Less is known about their relationships with hypertension control in the context of long-term management. OBJECTIVES: To identify whether patients with lower levels of activity or fitness are at risk for loss of control of hypertension. METHODS: Follow-up blood pressure measurements were recorded over the period of a year in a cohort of initially controlled hypertensive patients, under the care of 50 family physicians in a variety of practice settings. A questionnaire for a one-year recall of leisure time physical activity and the Step Test, an indirect measure of maximal oxygen consumption, were administered to the patients at the end of the period of blood pressure observations. The study group for the activity questionnaire consisted of 385 patients; 310 of whom undertook the fitness test. Sociodemographic, clinical and lifestyle factors were analyzed as potential confounders in the relationships of main interest in this study: between activity and fitness, respectively, with loss of control of hypertension. RESULTS: Sixteen per cent of patients (95% CI 12, 20) had an increase of 20 mmHg systolic or 10 mmHg diastolic from baseline to the average of three follow-up blood pressures, and 14% (95% CI 11, 18) had blood pressures above the entry thresholds on at least two of three follow-up visits. No associations were found between loss of control of hypertension and physical activity or cardiorespiratory fitness. CONCLUSIONS: Lower levels of physical activity and fitness are not associated with loss of hypertension control. The identification of patients at risk for loss of hypertension control, which could be useful in targeting selected groups for increased follow-up and in understanding the high prevalence of uncontrolled hypertension, requires further study.

Adult↗