I always thought a low heart rate was from having a big heart. Isn't that the case? Work out and your heart grows bigger and has to beat slower at rest. Am I missing something? Dr. Peat said the same thing.
I think a HR in the 70s is good for a middle aged adult or older adult because it indicates good thyroid function. I'm not sure there is any benefit to it. It is a sign of healthy metabolic rate, or can be.
If you look at the studies, many times higher HR is associated with greater morbidity and mortality. Because people with a high HR often are sick and sedentary.
It's the whole picture that counts and it's very complicated. Just like as people get old, a higher TSH can be associated with greater longevity for some reason.
https://academic.oup.com/jcem/article-abstract/94/4/1251/2596354
Design/Setting/Patients: We analyzed TSH, FT4, and TSH frequency distribution curves in thyroid disease-free Ashkenazi Jews with exceptional longevity (centenarians; median age, 98 yr), in younger Ashkenazi controls (median age, 72 yr), and in a population of thyroid disease-free individuals (median age, 68 yr) from the U.S. National Health and Nutrition Examination Survey 1998–2002 (NHANES controls).
Results: Serum TSH was significantly higher in centenarians [1.97 (0.42–7.15) mIU/liter] than in Ashkenazi controls [1.55 (0.46–4.55) mIU/liter] and NHANES controls [1.61 (0.39–6.29) mIU/liter] (median, 2.5 and 97.5 centiles) (P < 0.001). The TSH frequency distribution curve of centenarians was relatively similar in shape to controls but shifted significantly to higher TSH, including TSH concentration at peak frequency. The TSH distribution curve of the NHANES control group was superimposable to and not significantly different from the Ashkenazi controls. FT4 was similar in centenarians and Ashkenazi controls, and there was a significant inverse correlation between FT4 and TSH in both groups.
Conclusions: The TSH population shifts to higher concentrations with age appear to be a continuum that extends even to people with exceptional longevity.The inverse correlation between TSH and FT4 in our populations suggests that changes in negative feedback may contribute to exceptional longevity.