The observational data relating salt and blood pressure (excluding INTERSALT) are reviewed. Important methodological difficulties and biases are inherent to both across- and within-population studies and confuse their interpretation. Across-population studies are positive but rely on data drawn from the international literature based on a variety of unstandardized field methods; they are prone ...

The use of current seat belts has been shown to be effective in reducing deaths and serious injuries to restrained car occupants by 50% compared to unrestrained. Real world accident studies have identified limitations to the performance of set belts. This has led to the next major evolution in restraint design which is the development of the intelligent restraints. The options for intelligent r...

In randomized treatment studies the randomization of subjects to the different treatment conditions ensures that the treatment groups are comparable in their baseline characteristics—measured or unmeasured—so we can confidently attribute differences in treatment outcomes to the assigned treatments. In contrast, subjects in observational studies are not randomly assigned to the treatment groups ...