Epidemiological studies relating a particular exposure to a specified disease may present their results in a variety of ways. Often, results are presented as estimated odds ratios (or relative risks) and confidence intervals (CIs) for a number of categories of exposure, for example, by duration or level of exposure, compared with a single reference category, often the unexposed. For systematic literature review, and particularly meta-analysis, estimates for an alternative comparison of the categories, such as any exposure versus none, may be required. Obtaining these alternative comparisons is not straightforward, as the initial set of estimates is correlated. This paper describes a method for estimating these alternative comparisons based on the ideas originally put forward by Greenland and Longnecker, and provides implementations of the method, developed using Microsoft Excel and SAS. Examples of the method based on studies of smoking and cancer are given. The method also deals with results given by categories of disease (such as histological types of a cancer). The method allows the use of a more consistent comparison when summarizing published evidence, thus potentially improving the reliability of a meta-analysis.

Heartbeat perception has become the most widely studied example of visceral perception. In the present study scalp potentials contingent to the visceral event "heartbeat" were investigated. Scalp potentials, averaged time-locked to the EKG-R-wave, were studied at Fz, Cz, and Pz under four conditions: resting (baseline), heartbeat discrimination task, signal detection task, and heartbeat discrimination task after physical exercise. 22 subjects were assigned to the two groups "good" and "poor" perceivers, according to their performance in an initial heartbeat perception test. Event related potentials (ERPs) of "good" perceivers were more stable across conditions than those of "poor" perceivers. Peak latency within the range of 200 to 300 ms differed significantly between conditions. A principal component analysis performed on the ERP averages extracted five components. Subsequent ANOVAs across factor scores yielded significant main effects for the "groups" factor, experimental conditions and electrode sites. The strongest effects occurred over the frontal region in the latency range of 250-400 ms (following the EKG-R-wave). These were found to be not due to artifactual EKG influences.

Heartbeat synchronous potentials were found to be sensitive to differences in perceptual accuracy. Since heartbeat perception can be improved using appropriate training procedures, increased ability to perceive cardiac performance should also influence heartbeat-related potentials. In the present study, subjects in either of two groups had to press a button immediately after the occurrence of a heartbeat-feedback tone. Whereas the first group was given acoustical heartbeat-feedback throughout the entire training, the second group was provided with tone signals that became fainter during the course of the training phases. The better posttraining performance in heartbeat perception of the group receiving full-intensity feedback was also reflected in the evoked potentials. They differed markedly before and after training, especially between 250 to 400 ms (after the EKG-R-wave), the biggest effect being at Fz and F7. The findings are interpreted as the brain electrical reflection of an increased perception susceptibility to a cardiovascular signal occurring at about 200 ms after the R-wave.

IntroductionModified-risk tobacco products are expected to reduce exposure to harmful and potentially harmful constituents of cigarette smoke, and ultimately reduce the health burden of smoking-related diseases. Clinically relevant risk markers of smoking-related diseases inform about the risk profile of new tobacco products in the absence of in-market epidemiological data. The menthol Tobacco Heating System 2.2 (mTHS) is a modified-risk tobacco product in development as an alternative to cigarettes (conventional cigarettes [CCs]).MethodsIn this parallel-group study, Japanese adult smokers (23–65 years; ≥10 mCCs/day) were randomized to mTHS, menthol CCs (mCC), or smoking abstinence (SA) for 5 days in confinement and 85 days in ambulatory settings. Endpoints included biomarkers of exposure to harmful and potentially harmful constituents and clinically relevant risk markers of smoking-related diseases.ResultsOne-hundred and sixty participants were randomized to the mTHS (n = 78), mCC (n = 42), and SA (n = 40) groups. Switching to the mTHS was associated with reductions in biomarkers of exposure compared with continuing mCCs. Reductions in 8-epi-prostaglandin F2α (biomarker of oxidative stress), 11-dehydro-thromboxane B2 (biomarker of platelet activation), soluble intracellular adhesion molecule-1 (biomarker of endothelial function), and an increase in high-density lipoprotein cholesterol (biomarker of lipid metabolism) and forced expiratory volume in 1 second (biomarker of lung function) occurred in the mTHS group compared with the mCC group. The changes in the mTHS group approached those in the SA group.ConclusionsSwitching from mCCs to mTHS was associated with improvements in clinically relevant risk markers linked to mechanistic pathways involved in smoking-related diseases.ImplicationsIn this three-way randomized study, switching from menthol cigarettes to mTHS for 5 days in confinement and 85 days in ambulatory settings was associated with reductions in biomarkers of exposure to cigarette smoke, and changes were observed in clinically relevant biomarkers of oxidative stress (8-epi-prostaglandin F2α), platelet activity (11-dehydro-thromboxane B2), endothelial function (soluble intracellular adhesion molecule-1), lipid metabolism (high-density lipoprotein cholesterol) and lung function (forced expiratory volume in 1 second), similar to the SA group. The results suggest that switching to the mTHS has the potential to reduce the adverse health effects of conventional cigarettes.

We use Population Health Impact Modelling to assess effects on tobacco prevalence and mortality of introducing a Reduced Risk Tobacco Product (RRP). Simulated samples start in 1990 with a US-representative smoking prevalence. Individual tobacco histories are updated annually until 2010 using estimated probabilities of switching between never/current/former smoking where the RRP is not introduced, with current users subdivided into cigarette/RRP/dual users where it is. RRP-related mortality reductions from lung cancer, IHD, stroke and COPD are derived from the histories and the assumed relative risks of the RRP. A basic analysis assumes a hypothetical RRP reduces effective dose 80% in users and 40% in dual users, with an uptake rate generating ∼10% RRP and ∼6% dual users among current users after 10 years. Sensitivity study changes in tobacco prevalence and mortality from varying effective doses, current smoking risks, quitting half-lives and rates of initiation, switching, re-initiation and cessation. They also study extreme situations (e.g. everyone using RRP), and investigate assumptions which might eliminate the RRP-related mortality reduction. The mortality reduction is proportional to the dose reduction, increasing rapidly with time of follow-up. Plausible increases in re-initiation or dual users' consumption, or decreased quitting by smokers would not eliminate the drop.