Predictive and prognostic value of leptin status in asthma.

Asthma is closely associated with inflammation. We evaluated the predictive and prognostic value of leptin status in asthma. We searched the electronic databases for articles that determined the leptin level in asthma cases through May 2020. We compared the differences of leptin level between asthma and non-asthma controls, as well as between severe and mild asthma cases. We also investigated the impact of age and gender on these differences by using meta-regression analysis. 59 studies were included in our pooled analysis. Asthma cases demonstrated significantly higher leptin level than that in non-asthma controls among overall populations (SMD:1.061, 95% CI: 0.784-1.338, p < 10), Caucasians (SMD:0.287, 95% CI: 0.125-0.448, p = 0.001), Asians (SMD:1.500, 95% CI: 1.064-1.936, p < 10) and Africans (SMD: 8.386, 95% CI: 6.519-10.253, p < 10). Severe asthma cases showed markedly higher leptin level than that in mild asthma cases among overall populations (SMD:1.638, 95% CI: 0.952-2.323, p < 10) and Asians (SMD:2.600, 95% CI: 1.854-3.345, p < 10). No significant difference of leptin level between severe and mild asthma was observed in Caucasians (SMD:-0.819, 95% CI: -1.998-0.360, p = 0.173). Cumulative analyses yielded similar results regarding the difference of leptin status between asthma and non-asthma controls, as well as between severe and mild asthma cases among overall populations. Age and male/ female ratio were not associated with the difference of leptin status between asthma and non-asthma controls (coefficient:-0.031, 95% CI: -0.123-0.061, p = 0.495; coefficient:0.172, 95% CI: -2.445-2.789, p = 0.895), as well as between severe and mild asthma cases among overall populations (coefficient:-0.072, 95% CI: -0.208-0.063, p = 0.279; coefficient: 2.373, 95% CI: -0.414-5.161, p = 0.090). Asthma demonstrated significantly higher level of leptin than that in non-asthma controls among overall populations, Caucasians, Asians and Africans. Severe asthma cases showed markedly higher leptin level than that in mild cases among overall populations and Asians. Leptin may be a risk predictor and prognostic marker of asthma. Early monitoring and intervention of leptin may be needed for asthma.