There are some limitations in our study. First, our
outcome is self-reported. However, abundant evidence
indicates that self-reported information about HTN diagnosis
is valid for epidemiologic studies,30 particularly
among highly educated populations.31 Given the high educational
level of our participants and access to universal
healthcare in the Spanish population, we can assume the
validity of self-reported HTN diagnoses. In fact, considering
a medical diagnosis of HTN as the outcome, instead
of using single BP measurements, decreases the chance of
finding false positives. In a validation study conducted in
a randomly selected subsample of our cohort, we observed
acceptable positive and negative predictive values for selfreported
medical diagnoses of hypertension, even when
our gold standard, which was a repeated direct measurement,
missed true cases of hypertension. Nevertheless, some degree of information bias most likely exists. This
could be an important problem if those who engage more
frequently in sedentary behavior receive closer medical
attention, because it would be easier for them to be diagnosed
as hypertensive compared with those who are less
sedentary.