In this cross-sectional study, no statistically significant association was found between whole blood iron concentrations and FBG. The results were inconsistent with the predictions because whole blood iron may be affected by other factors such as inflammation, infection, medication use, diet, and chronic disease. However, the true link between iron in the body and FBG remains to be examined. A more accurate way to measure iron in the body is to measure tissue iron through a liver biopsy or bone marrow aspirate [17]. Perhaps in the future we can use liver biopsies and bone marrow aspiration to study whether there is a link between iron and FBG.

However, age was inversely related to whole blood iron levels, with significant gender differences. In particular, the whole blood iron levels in men over 60 years old showed a downward trend within the reference range, while the decrease was more obvious in women of the same age group. This supports existing literature indicating that older women are more likely to be iron deficient than men, with a global prevalence of 15–18% [18].

For the female population, we found that there was a study that showed the dysregulation of serum iron and hepcidin concentrations in obesity and inflammation [19]. At the same time, relevant studies have shown that healthy obese women is associated with elevated serum hepcidin, inflammation, dyslipidemia, and depressed serum iron concentrations [20]. Whether there is a similar association between obesity and whole blood iron deserves investigation. In the future, we need to assess obesity in older women in this population and consider it as a contributing factor after controlling for obesity.

The slight elevation of whole blood iron in men aged 85–93 years old deserves our attention. Excessive iron accumulation can also lead to deposition in extrahepatic organs such as the spleen, endocrine glands, and heart [21]. Iron overload is caused by an excess of iron in the blood, which triggers ferroptosis(a form of cell death). This occurs when intracellular levels of lipid reactive oxygen species(L-ROS) levels exceed the antioxidant capacity of glutathione-dependent peroxidase(GPX4), disrupting cellular redox balance and leading to iron-induced cell death [22]. Therefore, elderly men over 85 years old in this area may need to have their heart and liver function tested at the same time. This is to prevent iron overload due to increased iron levels in whole blood, which can lead to damage to the heart, endocrine glands and liver.

Although reduced whole blood iron levels may indicate the presence of anemia, measurement of serum ferritin is the most accurate method of diagnosing iron deficiency anemia and its relationship to chronic anemia [23]. Serum ferritin levels can be determined in future studies. This was used to help verify that whole blood iron levels decrease with age, causing anemia. This may play a role in the early prevention of anemia in the elderly.

Previous studies have shown that age-dependent and sex-specific changes in tissue iron in different strains of mice. Studies show that there are significant gender differences between BALB/c and DBA/2J strains [24]. Age was considered a potential confounder that could affect the study results. Whole blood iron concentrations may vary among different age groups. To reduce the effects of gender on the relationship between whole blood iron and FBG, participants in this study were stratified by gender.

Field surveys in the Chinese communities provided valuable physical examination and highly reliable whole blood iron data. The use of whole blood iron levels as an independent marker of short-term iron deficiency anemia risk may be useful in high-risk populations, as these groups were the primary targets of prevention strategies. Whether the association between lower whole blood iron levels and age is causal or a marker of age-related chronic disease burden associated with aging remains controversial. Findings from this region have significant implications for healthcare practice in this community.

However, the study had limitations. This study exclusively focused only on the older population in one community, which may limit the generalizability of the results. The sample size was considered insufficient given the multi-factorial nature of whole blood iron levels and the individual differences in iron levels in older adults. The impact of dietary habits on iron levels has not been thoroughly studied, so rigorous prospective studies are needed to validate the observed associations.