Deadly heart attacks are more common on a Monday

From the methods section of the abstract: “We excluded post-fibrinolysis patients, patients with old stents, and those who presented more than 24 hours after the onset of pain.”[edit: I misread the PDF version which included multiple abstracts, the methods I’m referring to was from a separate study with the title cutoff, this specific abstract didn’t specify. But from below and table 1 in: https://jamanetwork.com/journals/jama/article-abstract/20140... which looked at 68,000 STEMIs, 3.1% presented > 12 hours and 8.4% had an unknown time of symptom onset. Wouldn’t explain the magnitude of effect seen in this study. Circadian effects on STEMI and increased incidence on Monday are not new observations.]

Don’t think late presentation STEMIs are that common to begin with for your argument to have logical sense, this is the worst form of a “heart attack”.

From this single center study presentations > 12 hours only comprised 10%.

https://www.ingentaconnect.com/content/wk/jcarm/2017/0000001...

Thanks for links to those extra studies. The 3.1% and 10% presented > 12 hours are averaged across all days of the week not just the Sunday to Monday gap which is likely to be greater given the reduction in public services in Ireland on a Sunday. Do you know of previous studies which report Monday as being particularly risky? I can only find references to time of day (circadian cycle) which obviously make sense given how many bodily processes are linked to a circadian cycle but I'm skeptical about a weekly cycle (which I find confusing to be referred to as circadian also)

What is the effect in this study? The linked article has no info, not even the doi.

I linked it in another comment, but that's now a flag-hidden thread, so: https://heart.bmj.com/content/109/Suppl_3/A78.abstract

They include an off-hours subgroup which comprises of weekday after hours as well as weekends and represents 2/3rds of cases. They don't provide a further breakdown but in this after-hours group delayed presentation was even lower (2.9%) and they report statistical significance (although it looks like a multivariate P value at a quick glance). Unknown (10%) is hard to interpret what that actually means.

Just knowing the pathology of STEMI it's hard to buy that an effect of this size (in the Ireland study) is largely due patient's not seeking care on weekends unless you're somewhere extremely rural as this isn't your average heart attack.

If this was about ACS (acute coronary syndrome) in general I'd be more suspicious that patient delays are a relevant confounder, but we have other literature to support the trend (granted with some conflicting studies).

from [1]: > Many studies have shown an excess of cardiovascular events on Mondays (1,3,10,16,18,19). A relative trough has been seen on Saturdays and Sundays I compared with the expected number of cases. A similar pattern was seen in most subgroups irrespective of age, gender, cardiac medication, and in-fart characteristics (first or recurrent, Q or non-Q, site). The frequency of morning infarction is greater during the working week than on weekends, suggesting a superimposition of work-related stress on endogenous circadian rhythms.

>Circadian variation is found on all days of the week including weekends' when the morning peak is less obvious.

I haven't looked at the methodology of the cited studies but they include 6 references for your perusal.

[0]https://onlinelibrary.wiley.com/doi/abs/10.1002/clc.22 [1]https://onlinelibrary.wiley.com/doi/epdf/10.1002/clc.4960261... [2]https://europepmc.org/article/med/12061302

Thanks for the link. I'm not impressed by the effect at first sight. I certainly wouldn't want to exclude anything based on it. I mean, it's 13% more on Monday, which makes it "significant", but if you subtract the 3.1% you mention, you get close to the Sunday fraction, which isn't significant (p>0.05, which is a lousy statistic anyway). While it looks there's something going on, it's not enough to ignore the effects of data manipulation.

You're assuming that the 3.1% for > 12 hours is different between weekdays and weekends. While the study you're quoting grouped after-hours with weekends there were less delayed presentations in this subgroup compared to the M-F business hours group.

Other weekday numbers will also have delayed presentations included so you can't just "subtract 3.1" from one day and declare statistical insignificance.

What you can do is subtract it from every day as we know that 97% of STEMIs present within 12 hours.

As this is just an abstract we don't know what the authors did in this particular example but it's not the first study to suggest Mondays have the highest ACS rates.