Response by Rydén to Letter Regarding Article, “Periodontitis Increases the Risk of a First Myocardial Infarction: A Report From the PAROKRANK Study”
We have with satisfaction and a bit of surprise read the letter by Dizman and coauthors discussing our article, “Periodontitis Increases the Risk of a First Myocardial Infarction: A Report From the PAROKRANK Study.”1
Satisfaction, because we are happy that our report is acknowledged and discussed and grateful for the appreciative words on a “meticulous work on such a controversial subject.”
Surprise, because we never claimed that our data could be seen as proof of a causal relationship between periodontitis and cardiovascular disease, in this report studied as a patient’s first myocardial infarction. In the last part of the discussion, we did indeed write: “The major limitation is that PAROKRANK is an observational study, which can support but not prove the concept of a causal relationship.” We added that the ongoing follow-up of new cardiovascular events in the studied population may contribute further possibilities to get closer to an answer to the important question of whether there is a causal relationship or not.
In our opinion, the chosen case–control model is well suited to test hypotheses, including potential causal relationships, because confounders can be accounted for. It is evident that a cohort model would be ideal, but, because of issues discussed in our article, it is very unlikely that such a study will ever be performed.
Reverse causality may be a concern in case–control studies if there is a reason to suspect an impact of exposure (in this case, periodontitis) on the end point (in this study, a first myocardial infarction). Such an impact is very unlikely because we used a radiographic measure of periodontitis, and it takes time in the magnitude of years to develop modest or severe bone loss.
- © 2016 American Heart Association, Inc.
- Rydén L,
- Buhlin K,
- Ekstrand E,
- de Faire U,
- Gustafsson A,
- Holmer J,
- Kjellström B,
- Lindahl B,
- Norhammar A,
- Nygren Å,
- Näsman P,
- Rathnayake N,
- Svenungsson E,
- Klinge B