Effects of Gender and Other Confounding Factors on Leptin Concentrations in Alzheimer’s Disease: Evidence from the Combined Analysis of 27 Case-Control Studies
Affiliations: [a] College of Medicine and Health, Lishui University, Lishui Zhejiang, China
| [b] College of Engineering, Lishui University, Lishui Zhejiang, China
Correspondence:
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Correspondence to: Dr. Zhou Futao, College of Medicine and Health, Lishui University, Lishui City, Zhejiang Province, 323000, China. Tel.: +86 578 2131183; E-mail: zhft522@163.com.
Abstract: Leptin, as a link between fat mass and the brain, has been reported to be associated with gender. The gender differences in leptin levels between Alzheimer’s disease (AD) and healthy elderly controls are inconclusive so far. To quantitatively summarize the leptin data available from female and male patients with AD, we searched PubMed and EMBASE for articles published from inception to July 20, 2017. Data were extracted from 27 studies, consisting of 3,014 participants. The pooled results showed that the overall leptin levels were lower in AD (Hedges’ g = –0.481; p = 0.002) than in controls, and the leptin levels in whole blood and serum were decreased with moderate and large effect sizes (g = –0.677, –0.839; respectively; both of p-values <0.001) in AD compared with controls. In blood, there were significantly lower concentrations of leptin in female AD than in female controls (g = –0.590; p = 0.014), but not in male case-control group (g = –0.666; p = 0.067). Meta-regression analysis demonstrated that the decreased extent of leptin levels in AD paralleled the degree of the severity of dementia symptoms, as well as the alterations of body mass index (p-values ≤0.002). The findings provide strong evidence that 1) the blood concentrations of leptin are lower in female AD patients than in female controls; and 2) the greater the severity of dementia symptoms, the greater the decreases in the blood leptin levels. But more future investigations on the blood leptin levels in male AD patients is warranted.
