> The answer turns out to be rather mundane. Pap smears are not recommended for women older than 65, and heart failure onset is typically around age 65. The pap

> The answer turns out to be rather mundane. Pap smears are not recommended for women older than 65, and heart failure onset is typically around age 65. The pap smear just turns out to be a really good age bucketing signal to the model. Pap smears are also a really good sex bucketing signal, and there are lots of diseases that are more prevalent in one sex, so I would expect Pap smears to be correlated and anti-correlated with a lot of other diseases as well.