For the video version of this post, click here. There are two elements you can expect to see in almost any study: the first is some effect size - a measure of association between an exposure and outcome. The second is a subgroup analysis - a report of how that effect size differs among different groups. Sex is an extremely common subgroup to analyze - lots of things differ between men and women. But a really unique study appearing in the Journal of the American College of Cardiology suggests that sex might not matter when it comes to coronary disease. What really matters is gender.
The study, with cumbersome acronym GENESIS-PRAXY, examined 273 women and 636 men of age less than 55 who were hospitalized with Acute Coronary Syndrome (ACS). Sex was based on self-report, and was binary (man or woman). But gender isn’t sex. Gender is a social construct that represents self-identity, societal roles, expectations and personality traits, and can be a continuum - think masculine and feminine.
The authors created a questionnaire that attempted to assign a value to gender. Basically, questions like - “how much of the child-rearing do you perform” or “are you the primary breadwinner for your household” - in other words these are based on traditional gender norms - but that’s as good a place to start as any. A score of 100 on the gender scale was “all feminine”, and a score of 0 “all masculine”. Most of the males in the study clustered on the masculine end of the spectrum, while the females were more diverse across the gender continuum.
What was striking is that the primary outcome - recurrence of acute coronary syndrome within a year, was the same regardless of sex - 3% in men and women. But a greater degree of “femininity” was significantly associated with a higher recurrence rate. Feminine people (be they male or female) had around a 5% recurrence rate compared to 2% of masculine people. This was true even after adjustment for sex, so we’re not simply looking at sex in a different way - gender is its own beast.
What does it all mean? Well, it shows us that our binary classification of sex may be too limited in the biomedical field. Of course, there will always be hard and quantifiable physiologic differences between men and women. But what is so cool is that it’s the more difficult to quantify gender-related differences that may matter most when it comes to health and disease.
Of course, this conclusion is way too big to be supported by one small study with a 3% event rate. But given the surprising and really interesting nature of the results, I’m sure we’ll have many more studies of this sort following close behind.
For the video version of this article, click here.
Normally, in 150 seconds, I give a synopsis of a breaking study something that just hit the news. Today, were taking a different angle, and tackling a study that has had time to breathe for a while.
The Prospective Urban Rural Epidemiology, or PURE study, published in the Lancet reports on the association between grip strength and a variety of bad outcomes ranging from diabetes to cardiovascular disease, to death.
Its a big study, involving nearly 150,000 people across 17 countries. The headline-grabbing finding was an association between weaker grip strength and subsequent all-cause mortality. The take-home, for every 5 kg less grip strength you have, theres a 16% increased risk of death.
But once the study moved from the peer-reviewed and venerable pages of The Lancet into the press, things got a bit messy. So I want to apply some much-needed context.
Lets get one thing out of the way first. Grip strength is NOT the same as handshake strength. This is a grip strength dynamometer, used to precisely measure the maximum force the hand can generate, which is a product of a variety of factors including muscle mass and the length of the forearm:
A handshake is a social construct, and has nothing to do with anything. This was not a study about forceful handshakes.
Second this study describes an association. It is very probable that a strong grip says something about your overall health. It is NOT probable that grip strength is directly tied to outcomes. The article in no way implies that hand strengthening should be a public health intervention.
But the real issue here is applicability. With a study of almost 150,000 people, its not hard to find significant associations. The clinical question is: Can measuring grip strength help me risk stratify patients? Put another way, if I had two random patients in front of me, how often would the person with more grip strength live longer? If the answer is 50%, thats chance, and the test is useless. If the stronger person always lives longer, its a perfect test and we should be doing it on everyone all the time. The truth, of course, is somewhere in the middle.
But heres the letdown. The authors dont report their full, multivariable model, so we dont know how well grip strength categorizes risk, only that there is an association there. Based on the authors comparison with blood pressure as a risk factor, I suspect that accounting for grip strength would address some of the randomness in figuring out who dies when, but only a small amount, probably around 2-5%.
So whats impressive about this study isnt the results. That stronger people live longer is not particularly exciting. Whats impressive is the logistics. 150,000 people, 17 countries, prospectively collected outcomes. This is good, if not revolutionary work. So despite the flaws of the reporting in the press, we can still hand it to the researchers.