It's 25% higher on that day. For all that statistic tells you though, it might just be bringing forward a heart attack you would otherwise have had the following week.
1.25*(a really tiny risk of a heart attack on a given day)
This same numerical trick happened when the WHO classified red meat as a carcinogen "in the same category as" cigarettes, and it was stated that it increased your risk of some cancer by ~50% (or something), but the baseline risk is so low that it's a lot less dramatic than it sounds.
This. When I asked a doctor, who was suggesting 'a certain med would reduce chances of some cardio incident by some 10s of percent' (I don't remember, specific details), as to what is the base percent if would be affecting, he sort of evaded the answer.
