Total Fluid and Water Consumption - Assignment Example

Total Fluid and Water Consumption Case-Control Study: Total Fluid and Water Consumption and the Joint Effect of Exposure to Disinfection By-Products on Risk of Bladder Cancer Submitted By (make sure your name and date are included here): Research Question: The following study had two major objectives: 1) to ascertain the relation between total fluid and water consumption and bladder cancer risk and 2) to determine whether exposure to chlorinated by-products such as trihalomethane (THM), which is present in tap water might increase the risk of developing bladder cancer. Health Outcome of Interest: The major health outcome of the research was focused on the proposed risks associated with bladder cancer and to ascertain whether they are truly effective in causing the disease. Exposure(s) of Interest: The subjects recruited for the case study were exposed to trihalomethane, a by-product produced during the chlorination of water, which is done for the purpose of disinfection. Diagnostic Criteria for Cases: Patients who were histologically confirmed to have primary bladder cancer were recruited as the case population for the study and they were identified with the help of urologic services. The other inclusion criteria’s for the recruitment of the case population were: age group between 20 and 80 years and they must reside within the geographical area surrounding the hospital. Case Ascertainment (include whether this was a single site or multi-site study): The study was a multi-center case-control study conducted in Spain and the subjects were recruited from 18 participating hospitals located at five different geographic regions in and around Spain. The cases were recruited through regular reviews of the discharge and pathology records in hospitals at by the research staffs who were involved in the study. Number of Cases (include information, if available, about the number who participated and the number who refused; indicate whether any information was provided about those who refused to participate): The number of cases who participated in the study was 338 out of the 1,457 eligible cases who were interviewed. However the article does not provide any information about the eligible subjects who were not part of the subjects. The reason for their non-participation has not been mentioned. Control Population (type/number/selection): The control population was chosen from the same hospitals where the case subjects were recruited. The control group included patients who suffered from problems like hernias, orthopedic problems, circulatory disorders, and who were admitted to the hospital. Those who had problems that were related to the study were not chosen as controls. About 582 controls from 1,465 eligible controls were selected. Signed informed consents were obtained from both the case and control participants before onset of the study. Type(s)/Method(s) of Data Collection (e.g. questionnaire, medical records, whether or not there was any procedure for validating some or the data): During the initial interview demographic information and familial, medical, including smoking history, and occupational history of all the eligible participants were collected using computer assisted software. The short listed case and control population were then made to complete a food-frequency questionnaire. This included their diet intake during the past 5 years, specific beverages consumed including water and their quantity and frequency of consumption. Type of Data Analysis: Analysis of total fluid intake was calculated by multiplying the volume consumed and the frequency of intake. The overall individual beverages obtained during the personal interview and in the FFQ were summed up. As exposure to THM levels was also considered in the study, the annual average THM levels, water source history and the onset of water chlorination details were got from local authorities and water companies. The databases were then merged to obtain year-by-year average THM levels. The ml/L annual average residential THM level exposure of the study population since the age of 15 was then calculated. Odds ratio and confidence intervals were calculated to ascertain the relation between exposure to THM and bladder cancer risk using regression models while adjusting for variables like age and sex and all the confounding variables including smoking status and exposure to THM levels. Total fluid quintiles were calculated based on the distribution among the control population and they were categorized. Trend analysis was done based on the median value of the categorized variables. The relation between water intake volume and THM levels was found out by using logistic regression models. Results/Main Findings of Study: Most of the case population was current smokers compared to the control population. The amount of water intake was found to be similar among the control group with water being the major fluid consumed by both males and females. A 39% decrease in bladder cancer risk was observed for both sexes comparing the ratio between highest and lowest levels of total fluid intake. Exclusion of THM levels in the models did not have an effect on bladder cancer risk. When considering water intake alone, both males and females who consumed more than 1,400 ml of water per day were found to have a 53% decrease in risk and this only decreased further with increasing water intake. There was no statistical significance between smoking status and water intake. Subjects who resided in areas with elevated THM levels and who consumed less than 400 ml of water per day had more than a 2-fold increase in the risk of developing bladder cancer compared to those drinking the same amount of water but with lesser THM levels. Increased risk was also observed among those who consumed more than 400 ml of water with higher THM levels. Consumption of beverages other than water and the total fluid intake excluding water were not associated with increased risk. Assessment of Bias (selection/information): No possible indication of selection bias was observed in the study and the selection procedure suggests that ethical rules for a clinical study were followed. Pertaining to information obtained during the study, some extent of recall bias while reporting water intake during the previous years could have occurred. This could be more so with the case population as given their condition there would be a tendency to report consumption of bad water even if it was not so. They might tend to attribute their condition to consumption of bad water. Assessment of Confounders: An inverse relationship was observed between water intake and smoking status and higher intake of water containing high and low levels of THM decreased the risk of bladder cancer. Comments: The study objective was realized with the finding that amount of water consumed did not relate to bladder cancer risk and high water intake that contained variable levels of THM was found to lower the risk of bladder cancer irrespective of the smoking status of the subjects. Reference: Michaud, D.S., Kogevinas, M., Cantor, K.P., Villanueva, C.M., Glacia-Closas, M., Rothman, N et al. (2007). Total Fluid and Water Consumption and the Joint Effect of Exposure to Disinfection By-Products on Risk of Bladder Cancer. Environmental Health Perspectives, 115(11), 1569-1572. Read More