Introduction: Anemia is a common disease, as it affects 12.7% of men in an age-dependent manner. It has been reported that anemia is related to cardiovascular disease and increased mortality. In approximately one-third of anemia cases among older people, the cause of anemia is unexplained. Clinical data that reported that exogenous testosterone replacement in men with testosterone deficiency could induce polycythemia would be indirect evidence that shows low testosterone levels are a risk factor for anemia in men. However, there are few data concerning the endogenous testosterone effect on Hb or hematocrit (Hct) in men. Additionally, scant data are available concerning the relationship between anemia and low testosterone levels. Moreover, the aforementioned clinical data are limited by a cross-sectional study design, including a small number of men with low total testosterone levels, no adjustment for confounding factors, and an inappropriate sampling time of testosterone. Therefore, we conducted the present study to address the aforementioned limitations of previous studies using a large dataset and propensity score matched case-control study method.
Methods: Data from 8727 middle-aged men who had undergone health checkups were analyzed. Hb, Hct, testosterone, basic blood chemistry, blood pressure, and body mass index (BMI) were assessed. We estimated the glomerular filtration rate (GFR) using the Modification of Diet in Renal Disease equation. Of the 8727 men considered, 8368 formed the cohort for propensity score matching, including 966 men with low testosterone (testosterone level <3.5 ng/mL, case) and 7402 men with normal testosterone levels (testosterone level =3.5 ng/mL, control); ultimately, however, members of the case and control groups were matched at a 1:2 ratio by propensity score.
Results: After matching, the groups were evenly distributed with respect to age, BMI, estimated GFR, hypertension, and diabetes. After matching, the mean Hb and Hct of the case group were significantly lower than those of the control group (15.0±1.1 g/dL vs. 15.3±1.0 g/dL, P<0.001; 43.5±2.9% vs. 44.4±2.8%, P<0.001, respectively). Additionally, the incidence of anemia (Hb <13 g/dL) was significantly greater in the case group (1.2% vs. 3.0%, P=0.001). Finally, the relative risk of anemia in the case was 2.4 compared to the control.
Conclusions: Low testosterone is significantly and independently related to low Hb, low Hct, and anemia in middle-aged men. Our data suggest the need for screening for anemia in middle-aged patients with testosterone deficiency and vice versa.
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