Association between hemoglobin level and cognitive profile in old adults: A cross‐sectional survey

Abstract

Objective In the present study, the association between Hemoglobin (HGB) level and cognitive profile was investigated and whether it affected the dementia risk in older adults. Methods A cross‐sectional population‐based survey that included 3519 individuals ≥65 years of age was conducted in 2019. Basic demographic characteristics were collected. The neuropsychological assessments and blood tests were administered to evaluate cognition and HGB level. Generalized additive models were used to analyze the non‐linear association between HGB levels and cognitive function. Logistics regression models were utilized to analyze the associations between HGB level and dementia risk. Results Overall, 459 (12.7%) participants were diagnosed with dementia and there were more females (54.7%) than males (45.3%). The number of subjects with anemia (3%) or hyperhemoglobinemia (5.2%) was higher than participants with normal HGB level. A visual representation of the relationship between HGB level and Mini‐Mental State Examination (MMSE) score showed an inverted U‐curve, which is more evident in female. Logistics regression models showed that anemia (odds ratio, OR = 1.826, 95% confidence interval, CI: 1.166–2.860, p < 0.01), but not hyperhemoglobinemia, significantly increased the risk of dementia. These trends were not the same for males and females. An abnormal HGB level had greater effects in females, resulting in higher risk of dementia for females with anemia or hyperhemoglobinemia than subjects with normal HGB level including males. Conclusion Both low and high HGB levels can lead to cognitive decline in the incidence of dementia, indicating an inverted U‐shaped curve association may exist between HGB level and global cognitive profile.

Comment on “association between hemoglobin level and cognitive profile in old adults: A cross‐sectional survey”

“…association between Hemoglobin (Hgb) level and cognitive profile and whether it affected the dementia risk in older adults. 1 They found both low and high Hgb levels can lead to cognitive decline in the incidence of dementia. 1 These results make a valuable contribution to the literature, but some issues should be considered when evaluating Hgb values and its clinical implications in older adults.…”

An Examination of the Non-linear Relationship Between Cognition and Total Hemoglobin Among the Cognitively Normal Older Adults by Gender

“…In contrast, an abnormally high Hgb level of 16 g/dL or above for male adults and 15 g/dL for female adults is considered as hyperhemoglobinemia, which can cause blood thickness and impaired blood circulation to the brain (Qin et al, 2019). Among older adults, the level of Hgb has been prospectively associated with cognitive decline (Yang et al, 2022). For example, there was a significant association between anemia (<13 g/dL for males and <12 g/dL for females) and global cognitive function and episodic memory among Chinese middle-aged and older adults (Qin et al, 2019).…”

“…For example, there was a significant association between anemia (<13 g/dL for males and <12 g/dL for females) and global cognitive function and episodic memory among Chinese middle-aged and older adults (Qin et al, 2019). In addition, both anemia (<12 g/dL for males and <11 g/dL for females) and hyperhemoglobinemia (>16 g/dL for males and >15 g/dL for females) have been strongly associated with poor global cognitive function (Yang et al, 2022).…”

“…In contrast, high hemoglobin level may be associated with cognitive decline through potential ischemic and hypoxic mechanisms as polycythemia vera has been associated with an increased risk of cerebral thrombosis (Shah et al, 2011). All of these explanations suggest that the use of statistical methodology suitable for examining the potential underlying non-linear relationship is needed (Qin et al, 2019; Shah et al, 2009; Yang et al, 2022).…”

“…These mixed findings may indicate that the relationship between Hgb and cognition is highly likely to be non-linear (Qin et al, 2019;Shah et al, 2009;Yang et al, 2022). Some explanations regarding non-linearity could include threshold effect below and above a certain level of Hgb (Zakai et al, 2013), inverted U-shaped curve in the relationship between Hgb and cognition (Shah et al, 2009), differential effects of Hgb in different brain regions (Ward et al, 2020), and theories related to low and high Hgb and their effect on brain structure (Gattas et al, 2020;Shah et al, 2011).…”