Shih-Jen Tsai, MD, Department of Psychiatry, Taipei Veterans General Hospital, No. 201, Shih-Pai Road, Sec. 2, Taipei 11217, Taiwan. Email: firstname.lastname@example.org
Lower hemoglobin (Hb) levels are a common feature in the elderly. The present study recruited 180 healthy elderly men. Participants were assessed using the Geriatric Depression Scale, the Cognitive Abilities Screening Instrument Chinese version, and the Wechsler Digit Span Task test. The mean age of the participants was 85.8 years (SD = 10.5). Pearson's correlation tests demonstrated that Hb concentrations negatively correlated with Geriatric Depression Scale (r = −0.245, P = 0.001), but did not correlate with Cognitive Abilities Screening Instrument, Forward or Backward Digit Span tests. Lower Hb levels, therefore, were associated with depression in the elderly men.
ELDERLY PERSONS COMMONLY have hemoglobin (Hb) concentrations slightly below the lower normal limit. A previous study reported that anemia is associated with changes in quality of life, increased risk of falls, infections, morbidity, and mortality in the elderly.1 However, few studies have investigated the influence of anemia on mental function in these individuals. The association between anemia and depression or cognitive function in the elderly remains controversial. A Japanese analysis indicated that lower Hb levels were significantly associated with depressive moods in elderly women at high risk of requiring care, though not in elderly men.2 A prospective population-based study in Italy showed that depressive symptoms were associated with anemia in a general population of older persons living in the community,3 while a cross-sectional study found that mild-grade anemia was independently associated with worse selective attention.4 Another sectional study in Turkey observed greater impairment to global cognition (as assessed by Mini-Mental Status Examination [MMSE]) in anemic than non-anemic groups in elderly nursing home patients.5
The above studies analyzed populations with medical problems or without excluding physical/mental problems. The physical/mental problems in these studied subjects may, therefore, have confounded the association between Hb and depression/cognition. To avoid these confounding factors, the current study analyzed the association of Hb levels with depression and cognitive performance in elderly Chinese men in relatively good health.
This study comprised 180 participants recruited from a veterans' home in Northern Taiwan. For each case, the clinical research assistant performed an extensive examination, including a diagnostic structured interview with the Mini-International Neuropsychiatric Interview (MINI),6 the Geriatric Depression Scale (GDS-15), the Clinical Dementia Rating Scale (CDR), and cognitive tests, including the Cognitive Abilities Screening Instrument Chinese version (CASI C-2.0) test,7 and the Wechsler Digit Span Task test (Forward and Backward). The CASI test is a 100-point cognitive test designed for cross-cultural studies and adapted in Chinese for individuals with little or no formal education.8 Exclusion criteria included the following: (i) presence of diagnoses on Axis I of the DSM-IV or alcohol abuse/dependence; (ii) severe medical conditions, including advanced-stage cancer, renal, liver, hematological disease and heart failure; (iii) neurobiological disorders (stroke or Parkinson's disease); and (iv) CDR > 0.5 or CASI C-2.0 ≤ 50 to exclude possible dementia. All participants had sufficient visual and auditory acuity for cognitive testing. A standard procedure was used to collect blood samples for Hb measurement. This study was approved by the local institutional review board. Informed consent was obtained from all subjects prior to commencement.
Pearson's correlations were conducted to identify correlations between Hb concentration and cognitive/depressive ratings. Data are presented as mean (SD), with the criterion for significance set at P < 0.05 for all tests.
The subjects were 180 men aged between 65 and 98 years (mean = 85.8; SD = 10.5), with an average of 5.1 years of education (SD = 4.6; ranged from 0 to 16 years of schooling). Cognitive function tests showed that the mean total CASI score was 85.3 ± 6.6 (range = 68–98). Hb concentrations ranged from 6.1 to 17.3 g/dL, with an average of 13.5 g/dL (SD = 1.8 g/dL). Mean scores for GDS-15, Digit Span Forward test, Digit Span Backward test and CDR were 2.9 (SD = 2.7), 11.4 (SD = 3.0), 3.4 (SD = 2.1) and 0.1 (SD = 0.2), respectively.
Pearson's correlation tests demonstrated that Hb concentrations negatively correlated with GDS-15 (r = −0.245, P = 0.001) (Fig. 1). Among the 180 subjects, 56 were current smokers. After controlling for age, education years and smoking status, the correlation was still significant (r = −0.261, P < 0.001). Hb concentrations did not correlate with cognitive tests, including CASI (P = 0.879), Forward Digit Span (P = 0.286) and Backward Digit Span (P = 0.172). After controlling for age, education years and smoking status, the correlation was still insignificant (data not shown). A linear-regression analysis performed with age, education years, and Hb concentrations as the predictor variables identified education years as the only significant predictor of CASI score (P < 0.001).
The results of this study indicate that Hb concentrations negatively correlated with depression, as evaluated using GDS-15, and did not correlate with cognitive function. Our findings are consistent with those of a previous study on English community-dwelling older adults (3816 men and women; aged 65.4 ± 9.0 years),9 but differed from those from a Japanese analysis that showed no significant association between Hb levels and depressed mood in elderly men at a high risk of requiring care.2 This discrepancy may be caused by sample differences, ethnic differences, or different depression ratings. The underlining mechanism of the link between lower Hb levels and depressive mood still requires full elucidation. Anemia could worsen symptoms of fatigue, irritability, and poor concentration, which are significant components of depression. Furthermore, anemia reduces brain oxygenation,10 which may affect brain function for stress coping. In a large longitudinal prospective study of English community-dwelling older adults, anemia did not predict risk of depression over 2 years of follow up.9 Therefore, the causal correlation may be in the reverse direction (depression causes anemia). For example, lower Hb may be a consequence of poor dietary iron intake among subjects with more depressed moods.
Although certain studies demonstrated that lower Hb levels were associated with poorer cognitive function in old age,4,5 the data of the present study did not reveal any significant association between Hb levels and cognition in its elderly healthy male subjects. This result may be caused by differences in sample populations between the studies and varying cognitive ratings used.
This study has several limitations. First, the sample comprised a population of Chinese elderly men living in a veterans' home; therefore, any association between Hb levels and depression in women or other populations requires further confirmation. Second, patient assessments did not include the causes of anemia. Third, this cross-sectional study could not identify the causal correlation between anemia and depression.