Analysts of epidemiologic data often contend with the problem of estimating the independent effects of many correlated exposures. General approaches include assessing each exposure separately, adjusting for some subset of other exposures, or assessing all exposures simultaneously in a single model such as semi-Bayes modeling. The optimal strategy remains uncertain, and it is unclear to what extent different reasonable approaches influence findings. We provide an empirical comparison of results from several modeling strategies.
In an occupational case-control study of lung cancer with 184 exposure substances, we implemented 6 modeling strategies to estimate odds ratios for each exposure-cancer association. These included one-exposure-at-a-time models with various confounder selection criteria (such as a priori selection or a change-in-the-estimate criterion) and semi-Bayes models, one version of which integrated information on previous evidence and chemical properties.
While distributions of odds ratios were broadly similar across the 6 analytic strategies, there were some differences in point estimates and in substances manifesting statistically significant odds ratios, particularly between strategies with few or no occupational covariates and those with many. Semi-Bayes models produced fewer statistically significant odds ratios than other methods. A simple semi-Bayes model that shrank all the 184 estimates to a common mean yielded nearly identical results to one that integrated considerable prior information.
Different modeling strategies can lead to different results. Considering the conceptual and pragmatic difficulties of identifying confounders, these results suggest that it would be unwise to place uncritical reliance on any single strategy.
Various drugs have been approved for the treatment of Alzheimer's disease (AD) in the United States and Canada, including donepezil and rivastigmine, although questions remain as to their efficacy, effectiveness, and long-term benefits.
The goal of this study was to conduct a best-evidence synthesis of data on the efficacy and cost-effectiveness of donepezil and rivastigmine in the treatment of AD.
Relevant published randomized controlled trials (RCTs) and Phase IV open-label extension studies (excluding abstracts) were identified through searches of MEDLINE, HealthSTAR, and PsycINFO for the period January 1984 to October 2001. The bibliographies of retrieved articles were searched for additional publications. For inclusion in the best-evidence synthesis, clinical trials had to pass a blinded quality assessment (score > or =5 on the Jadad scale) and use National Institute of Neurological and Communicative Disease and Stroke-Alzheimer's Disease and Related Disorders Association diagnostic criteria. Economic studies were selected using National Health Service Centre for Reviews and Dissemination criteria for reporting critical summaries of economic evaluations.
Nine RCTs of donepezil and 2 of rivastigmine were identified and met inclusion criteria for the best-evidence synthesis. Eight donepezil trials and both rivastigmine trials included patients with mild AD (Mini-Mental State Examination [MMSE] score, 15-27) or moderate AD (MMSE score, 8-14); 1 donepezil trial included patients with moderate or severe AD (MMSE score, 0-7). In the RCTs of donepezil, the mean decrease in scores on the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) was greater with active treatment than with placebo (lower scores indicate less cognitive deterioration). In the RCTs of rivastigmine, ADAS-cog scores decreased over the follow-up period with both active treatment and placebo; however, scores decreased more with active treatment. Three Phase IV studies of donepezil and I Phase IV study of rivastigmine were identified. Their results were consistent with those of the RCTs. Ten economic studies (7 donepezil, 3 rivastigmine) were identified and reviewed. In 4 of the donepezil studies and all 3 rivastigmine studies, use of the drug cost less than a no-drug strategy.
The efficacy data indicate that both donepezil and rivastigmine can delay cognitive impairment and deterioration in global health for at least 6 months in patients with mild to moderate AD. Patients receiving active treatment will have more favorable ADAS-cog scores for at least 6 months, after which their scores will begin to converge with those of patients receiving placebo. Differences in methodology, types of direct or indirect costs included, and sources of cost data made it difficult to compare and synthesize findings of the economic studies; therefore, the cost-effectiveness data are inconclusive.
An investigation based on a large population-based case-control study in British Columbia, Canada, was conducted to identify high-risk occupations for lung cancer by histological subtypes. Subjects were 14,755 male incident cancer cases for whom lifetime occupational histories and information on smoking and relevant covariates were collected. Occupational associations for 2998 lung cancer cases, including histological subtypes, were assessed by logistic regression using other cancer cases, excluding smoking-related cancers, as controls. An excess risk of lung cancer was found among workers in metal processing, bakers, and ship deck crew for all histological subtypes, and construction workers, chefs and cooks, and medical workers for specific histological subtypes. Occupational associations that are unique to histological subtypes of lung cancer were identified. Owing to a scarcity of literature in this area, future research needs to focus on confirming these histological associations, and identifying the risk from key exposures found within these occupations (e.g., medical radiation, electromagnetic fields, and cooking fumes).
Tuberculosis (TB) remains a significant health burden among Inuit in Canada. Social determinants of health (SDH) play a key role in TB infection, disease and ongoing transmission in this population. The objective of this research was to estimate the prevalence of social determinants of Inuit health as they relate to latent TB infection (LTBI) among people living in residential areas at high risk for TB in Iqaluit, Nunavut.
Inperson home surveys were conducted among those who lived in predetermined residential areas at high risk for TB identified in a door-to-door TB prevention campaign in Iqaluit, Nunavut in 2011. Risk ratios for SDH and LTBI were estimated, and multiple imputation was used to address missing data.
261 participants completed the questionnaire. Most participants identified as Inuit (82%). Unadjusted risk ratios demonstrated that age, education, smoking tobacco, crowded housing conditions and Inuit ethnicity were associated with LTBI. After adjusting for other SDH, multivariable analysis showed an association between LTBI with increasing age (relative risk, RR 1.07, 95% CI 1.04 to 1.11), crowded housing (RR 1.48, 95% CI 1.10 to 2.00) and ethnicity (RR 2.76, 95% CI 1.33 to 5.73) after imputing missing data.
Among high-risk residential areas for TB in a remote Arctic region of Canada, crowded housing and Inuit ethnicity were associated with LTBI after adjusting for other SDH. In addition to strong screening and treatment programmes, alleviating the chronic housing shortage will be a key element in the elimination of TB in the Canadian Inuit Nunangat.
The incidence rate of active tuberculosis (TB) disease in the Canadian Territory of Nunavut has shown a rising trend over the past 10 years. In 2010 it was 60 times greater than the national incidence rate. The objective of the Taima (translates to "stop" in Inuktitut) TB study was to implement and evaluate a public health campaign to enhance existing TB prevention efforts in Nunavut.
A TB awareness campaign followed by a door-to-door screening campaign was carried out in Iqaluit, Nunavut. The aim of the campaign was to raise awareness about TB, and to provide in-home screening and treatment for people living in residential areas at high risk for TB. Screening was based on geographic location rather than on individual risk factors.
During the general awareness campaign an increase in the number of people who requested TB testing at the local public health clinic was observed. However, this increase was not sustained following cessation of the awareness campaign. Targeted TB screening in high risk residential areas in Iqaluit resulted in 224 individuals having TSTs read, and detection of 42 previously unidentified cases of latent TB, (overall yield of 18.8% or number needed to screen?=?5.3). These cases of latent TB infection (LTBI) were extra cases that had not been picked up by traditional screening practices (34% relative increase within the community). This resulted in a 33% relative increase in the completion of LTBI treatment within the community. The program directly and indirectly identified 5/17 new cases of active TB disease in Iqaluit during the study period (29.5% of all incident cases).
While contact tracing investigations remain a cornerstone of TB prevention, additional awareness, screening, and treatment programs like Taima TB may contribute to the successful control of TB in Aboriginal communities.
Cites: Eur Respir J. 2013 Jan;41(1):140-5622936710
Cites: Int J Tuberc Lung Dis. 2013 Jun;17(6):771-623676160