Effect of smoking on Brain-Derived Neurotrophic Factor (BDNF) blood levels: A systematic review and meta-analysis

I highly doubt that your doctor will recommend smoking to increase your BDNF levels.  And they didn't seem to test marijuana smoking to see if you could get two for one. 

 I assume your competent? stroke doctor has already given you everything you need on BDNF. But I'm sure I'm making an incorrect assumption. If your doctor doesn't know of all these BDNF stroke research articles there is a good reason!  PURE INCOMPETENCE!

• BDNF (169 posts to April 2011)

Didn't your competent? doctor prescribe marijuana years ago to help your stroke recovery?  Oh, you don't have a functioning stroke doctor, do you? 

• 13 reasons for marijuana (132 posts to April 2014)

• marijuana (150 posts to April 2011)

Effect of smoking on Brain-Derived Neurotrophic Factor (BDNF) blood levels: A systematic review and meta-analysis

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Abstract

Background

Brain-Derived Neurotrophic Factor (BDNF) is a neurotrophin that plays a crucial role in neuronal survival and plasticity. Previous studies have suggested that smoking may influence BDNF levels, but the findings have been inconsistent.

Methods

A comprehensive search of electronic databases was conducted to identify relevant studies. Inclusion criteria were applied to select studies that investigated the relationship between smoking and blood levels of BDNF. A random-effects model was used to estimate the overall effect size.

Results

A total of 23 studies were included. The meta-analysis revealed a significant association between smoking and increased blood levels of BDNF (standardized mean difference [SMD] = −0.38, 95 % confidence interval [CI] 0.15 to 0.62, p = 0.002). Subgroup analyses based on BDNF source showed a significant increase in plasma-derived BDNF levels (SMD = 1.02, 95 % CI 0.50 to 1.53, p = 0.0001), while no significant difference was observed in serum-derived BDNF levels (SMD = 0.02, 95 % CI -0.19 to 0.22, p = 0.87). The pooled analysis revealed a non-significant difference in blood levels of BDNF between former smokers and non-smokers (random-effects model, SMD = 0.21, 95 % CI -0.04 to 0.46, p = 0.1).

Conclusion

Smokers exhibited significantly higher plasma levels of BDNF compared to non-smokers. Further research is needed to elucidate the underlying mechanisms and explore the potential therapeutic implications of targeting BDNF in smoking.

Introduction

In 2019 alone, there were 1.14 billion smokers worldwide, an increase from 0.99 billion in 1990, with tobacco accounting for 13.6 % of all deaths in the same year (Reitsma et al., 2021). In 2020 this number increased to 1.18 billion (Dai et al., 2022). Smoking tobacco is a leading cause of ischemic heart disease, chronic obstructive pulmonary disease, lung cancer, and tracheal cancer, impacting an estimated 7 million lives a year on average (WHO/ Fact-Sheet/ Tobacco, n.d.). Although its toxic effects on the pulmonary and cardiovascular systems are well established, its association with neurological disorders is a point of contention, with studies highlighting its role in the development of Alzheimer's disease and, paradoxically, the prevention of Parkinsons disease (Hajdusianek et al., 2021).

BDNF, a member of the neurotrophin family, is a growth factor found in the nervous system and platelets, and plays a key role in synaptic plasticity, neuronal growth, and numerous functions related to neural differentiation and maturation (Park and Poo, 2013; Fujimura et al., 2002). Since the measurement of CNS levels is challenging, blood levels of BDNF are frequently used as a proxy, with multiple studies supporting a close correlation between peripheral and CNS levels (Gejl et al., 2019a). Blood BDNF levels have been proposed as a biomarker for several psychiatric disorders (Fernandes et al., 2015a; Polyakova et al., 2015; Fernandes et al., 2015b), with their fluctuations linked with a multitude of states (e.g., stress, response to treatment) (Zhang et al., 2016a; Lin and Huang, 2020) and lifestyle habits (Sandrini et al., 2018; Ornell et al., 2018; Sleiman et al., 2016). A variation in the BDNF gene known as a single-nucleotide polymorphism (SNP) resulted in changes to the intracellular transport and activity-dependent release of mature BDNF, impacting hippocampal function. Studies showed that chronic nicotine administration is likely to escalate the BDNF level, additionally, the chromosomal region 11p13, where the BDNF gene is situated, is likely to contain susceptibility genes associated with nicotine dependence, specifically (Xia et al., 2019). Studies evaluating the influence of smoking on BDNF levels (Umene-Nakano et al., 2010; Kim et al., 2007; Abdelkhalek et al., 2022; Al-Mshari et al., 2022) have led to conflicting results with some observing significantly elevated BDNF levels in smokers (Abdelkhalek et al., 2022), while others noted significantly lower levels (Umene-Nakano et al., 2010).

As far as our understanding extends, there has been no comprehensive review investigating the correlation between blood BDNF levels and smoking. This study is designed to address this gap by exploring the potential connection between blood BDNF levels and smoking. Additionally, it aims to investigate: a) potential differences in BDNF levels between former smokers and non-smokers, b) the impact of smoking cessation on blood BDNF levels, and c) examine potential changes in serum BDNF and plasma BDNF through subgroup analysis. Understanding the relationship between smoking and BDNF level may be useful for addiction treatment and also screening the patients who are considered to be high risk for cognitive impairment due to BDNF dysregulation.