這一段闡釋了為什麽a1c值低死亡率反而高，總結一下就是有一些基礎血紅蛋白病，慢性貧血性疾病，炎症，肝病，會引起血紅蛋白異常，因而引起糖化血紅蛋白A1c異常降低。這類人的死亡率高，不是因為他們血糖太低，而是因為本身的基礎疾病。正常人很少看到a1c會低於四。文章裏說調整了這些marker，還是死亡率升高，但是不是很確定為什麽。所以也沒有完全定論。其實大部分人都不用去擔心自己a1c太低
臨床上懷疑病人有血紅蛋白疾病，貧血性疾病時候，是不測a1c的，用其他方法監測血糖
It is not clear what biological processes may be underlying the association between low HbA1c and all-cause mortality. In the present study, participants with low HbA1c values had unfavorable profiles of red blood cell related factors, iron storage, and liver function. Red blood cell distribution width has been associated with an increased risk of morbidity and mortality19–22 and with inflammation.21 Younger red blood cells are typically larger and have more size variability compared with older red blood cells,20 which could affect red blood cell distribution width and HbA1c values.6,23 Also, iron stores were elevated among those with low HbA1c in the present study. Iron-deficiency anemia has been associated with increased HbA1c values among individuals without diabetes; however, patients with iron-deficiency anemia who were treated with iron therapy had decreases in HbA1c values.24,25 Also, ferritin was elevated among those with low HbA1c in the present study. Elevated ferritin has been associated with an increased risk of myocardial infarction26 and atherosclerosis,27 but it is also an acute-phase reactant and could be reflecting an inflammatory response. Finally, liver function enzymes were elevated and hepatitis C was more prevalent among those with an HbA1c <4.0% in the present study. Elevated ALT is frequently associated with fatty liver and an adverse cardiometabolic risk factor profile. ALT was positively associated with HbA1c levels among participants with and without diabetes in the British Women’s Heart and Health Study, with a stronger association noted among women without diabetes.28 Certain combination therapies for hepatitis C have been reported to temporarily lower HbA1c levels29; however, the low HbA1c-mortality association observed in the present study was still evident after excluding participants with hepatitis C. The overall biomarker profile of the participants without diabetes and an HbA1c < 4.0% is suggestive of red blood cell markers, inflammation, and liver function as part of the biological underpinning for the association noted in this study. However, the low HbA1c and all-cause mortality association observed in this study persisted after adjustment for lifestyle, cardiovascular, metabolic, red blood cell, iron storage, and liver function indices. The association also persisted after excluding participants with cancer, CVD, anemia, or hepatitis C in sensitivity analyses. Additional research is needed to explore the potential health effects of aberrations in red blood cell markers, inflammation, and liver function indices and associations with all-cause mortality among individuals with a low HbA1c.
