Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.
In a recent, excellent study that found handgun purchase to be a risk factor for violent death, Grassel and colleagues gave explanations for why their findings may have inaccurately characterized the impact of handgun purchase on violent death, leading to results that if anything underestimate the magnitude of the danger associated with buying a handgun.1 “The healthy handgun purchaser effect”, which we suggest is akin to the healthy worker effect, may be a source of bias as well. Bias from this source could produce results that either underestimate or overestimate the impact of a handgun purchase on violent death. When dead controls are used in a case-control study, the death rate due to the comparison cause(s) should be equal in the exposed and unexposed populations.2–6 If this assumption is met, the odds ratio (OR) can be used as an estimate of the mortality density (or rate) ratio:
where a and c are exposed and unexposed cases and b and d are exposed and unexposed controls, respectively, and TE and TĒ are the person-time contributed by exposed and unexposed subjects, respectively. We follow Morgenstern and use his notation,6 but notation used …