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Background: Long-term, low-level exposure to toxic elements in soil may be harmful to human health but large longitudinal cohort studies with sufficient follow-up time to study these effects are cost-prohibitive and impractical. Linkage of routinely collected medical outcome data to systematic surveys of soil quality may offer a viable alternative., Methods: We used the Geochemical Baseline Survey of the Environment (G-BASE), a systematic X-ray fluorescence survey of soil inorganic chemistry throughout England and Wales to obtain estimates of the concentrations of 15 elements in the soil contained within each English and Welsh postcode area. We linked these data to the residential postcodes of individuals enrolled in The Health Improvement Network (THIN), a large database of UK primary care medical records, to provide estimates of exposure. Observed exposure levels among the THIN population were compared with expectations based on UK population estimates to assess representativeness., Results: Three hundred seventy-seven of three hundred ninety-five English and Welsh THIN practices agreed to participate in the linkage, providing complete residential soil metal estimates for 6,243,363 individuals (92% of all current and former patients) with a mean period of prospective computerised medical data collection (follow-up) of 6.75 years. Overall agreement between the THIN population and expectations was excellent; however, the number of participating practices in the Yorkshire & Humber strategic health authority was low, leading to restricted ranges of measurements for some elements relative to the known variations in geochemical concentrations in this area., Conclusions: The linked database provides unprecedented population size and statistical power to study the effects of elements in soil on human health. With appropriate adjustment, results should be generalizable to and representative of the wider English and Welsh population.

Aims: To determine the incremental cost effectiveness of nicotine replacement therapy (NRT), bupropion and varenicline for preventing relapse to smoking when used by abstinent smokers, Design Setting and Participants: Cohort simulation and sensitivity analyses combining cost and health service data with systematic review estimates for the effectiveness of NRT, bupropion and varenicline when used by abstinent quitters to prevent their relapse to smoking., Measurements: Incremental health gain in Quality Adjusted Life Years (QALYs) generated by each drug compared to 'no intervention'., Findings: Bupropion resulted in an incremental QALY increase of 0.07 with a concurrent cost saving of £68; NRT and varenicline both caused incremental QALYs increases of 0.04 at costs of £12 and £90 respectively, although varenicline findings were based on data from a single clinical trial and require cautious interpretation. Even after extensive sensitivity analyses with substantial varying of key model parameters, cost effectiveness of all drugs remained. Cost effectiveness ratios only exceeded the UK National Institute of Clinical Excellence (NICE) benchmark of £20 000 per QALY when drug treatment effects were postulated to last for no longer than 1 year; or, for NRT and varenicline, efficacy was reduced to 10% of that observed in clinical trials., Conclusions: Bupropion, nicotine replacement therapy and varenicline appear cost effective at preventing relapse to smoking by smokers who are in quit attempts and have recently become abstinent; they have comparable cost effectiveness to smoking cessation interventions. Widespread use of these effective relapse prevention treatments could promote substantial health gain at an acceptable cost to health providers., (© 2011 The Authors, Addiction © 2011 Society for the Study of Addiction.)