To the Editor:
We read with great interest the study by Zhang and Peng et al.,1 but would like to express our concern regarding several points.
This study stated that in cities with central heating, negative temperature changes between neighboring days (TCN) was not associated with acute aortic dissection (AAD) in heating periods, but negative TCN was associated with increased AAD onset in non-heating periods. However, it is debatable whether central heating reduces risks as negative TCN did not significantly increase relative AAD risk, even in cities without central heating in winter (Fig. 4e).
Since there is an association between increased AAD onset and negative TCN over non-heating periods in cities with central heating (Fig. 4c), it is reasonable to assume this occurred during non-heating periods and was not an effect of central heating.
Are sudden drops in temperature during non-heating seasons associated with increased AAD onset? The Discussion states that low temperatures and sudden temperature drops affect autonomic nervous systems, which in turn causes elevated blood pressure. However, it is unclear whether this also applies during the non-heating season, particularly summer.
Reports from China suggests that above a certain limit, increased temperature is associated with elevated blood pressure2; there are even reports that summer increases in nighttime blood pressure are not due to temperature, but physical discomfort and poor sleep quality due to summer weather.3
Therefore, TCN may be a confounding factor for AAD development regardless of whether it occurs during non-heating or heating conditions.
Declaration of interests
The authors declare no conflict of interest.
We did not receive any funding sources that may influence the writing of the manuscript or the decision to submit for publication.
Tatsuya Fujikawa, the corresponding author, had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
References
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