Low BMI and death after heart attack

I wonder if people who get a heart attack even though they are underweight and healthy could have a particularly strong tendency to have heart problems. This might explain these findings. Another possibility is that they are more likely to succumb to poor hospital nutrition or exposure to disease organisms while in the hospital.

http://www.eurekalert.org/pub_releases/2016-04/p-lba041516.php

Public Release: 19-Apr-2016
Low BMI and death after heart attack
Being underweight is an independent risk factor for death after heart attack
PLOS

Low body mass index increases risk mortality after acute myocardial infarction (AMI), even after adjustment for other health factors that affect body weight, according to a study this week in PLOS Medicine. Emily Bucholz, Hannah Krumholz, and Harlan Krumholz of Yale University conducted a prospective cohort study of elderly patients hospitalized for AMI, analyzing short- and long-term mortality among underweight and normal weight patients (as measured by body mass index, BMI) while controlling for comorbid illness and frailty.

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