I had a somewhat similar question about exercise vs physically demanding work, since the former helps to have a healthy heart and the latter seems to do the opposite. Explanations I've found were tied to the average daily heart rate. Exercises are intense but it's only a few hours per week, and over time they tend to lower the average heart rate. Physical work is typically less straining but it takes a big portion of the week and as the result increases the average heart rate.

I guess the problem of exercise (intense but short) vs chronic stress (moderate but 24x7) could have a similar explanation.