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Background

I have had a Fitbit heart tracker for several months. Typically, it reports my resting heart rate around 60 bpm, with a standard deviation of 1-2 bpm. A month ago, I got some kind of strange flu/cold hybrid, and starting about the same time I noticed symptoms (maybe a day before), my resting heart rate rose to 67, again with a standard deviation of 1-2 bpm. My primary symptoms lasted for 3-5 days, but I had minor symptoms that lasted for two weeks afterward. After the secondary symptoms went away, my resting heart rate dropped back to 61–62.

My Question

Is it normal for a cold or flu to noticeably elevate a person’s resting heart rate, and if so, why/how?

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  • Did you have a fever with this illness? – Carey Gregory♦ Feb 14 '18 at 23:14
  • Oddly, I had the other symptoms of the flu without a fever, including quite swollen lymph nodes in my armpit (somewhat normal for me with flu). – jvriesem Feb 15 '18 at 20:23
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Yes.

Most inflammatory processes (including viral infections) can cause elevation of heart rate via cytokines and activation of the sympathetic nervous system. (That's an oversimplification of a complex process.) Temperature regulation involves the hypothalamus as well, and fever (which is mediated by some of the same cytokine mechanisms) is often correlated with an increased HR.

A marginal increase of resting HR is not usually clinically significant. Resting HR of an individual can change with level of fitness, as well. However an increase of resting rate by 20, or resting HR over 100 would be more indicative of a systemic inflammatory response; however, whether that's a concerning finding or just an expected effect of your body fighting infection depends on other factors including individual risk factors, medicines, medical/surgical history etc. Someone who is concerned should review it with their doctor.

Note: I'm having difficulty finding references to cite outside of paywalls of textbooks, UTD, journals. Suggestions welcomed!

http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2796.2010.02321.x/full#js-feedback

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  • Flu can cause myocarditis – Graham Chiu Feb 17 '18 at 15:43
  • Most paywalls have been breached, and as pointed out here, subscription journals are doomed. – Count Iblis Feb 17 '18 at 18:53
  • @CountIblis That is in way true. But it is even more effective to condemn the publishers to damnatio memoriae and not cite from them, if possible. A middle ground might be reached by using unpaywall. That is also less legally troubled. Jurisdictions differ, some of these services you mentioned might be or will be blocked, get or taken down etc. – LаngLаngС Feb 18 '18 at 1:29

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