A systematic review and meta-analysis of serum cholesterol and triglyceride levels in patients with Parkinson's disease

Abstract

Objectives: Numerous studies have reported that lipid metabolic abnormalities may play an important role in the development of Parkinson's disease (PD), with mixed results. This meta-analysis aims to systematically assess the relationship between serum cholesterol or triglyceride and the PD risk and to further determine the role of dyslipidemia in potential predictive value.

Methods: This research systematically consulted and screened observational studies to evaluate the association of serum lipids with the risk of PD as of April 01, 2020 based on the inclusion and exclusion criteria. Two researchers screened and extracted the data independently. Then this article summarized the characteristics of all clinical studies and collected the corresponding data to perform pooled and sensitivity analyses. The meta-analysis was performed by using the RevMan 5.3 software after data extraction, quality assessment and analysis of publication bias.

Results: Twenty-one related studies (13 case-control and 8 cohort studies) were selected with a total of 980,180 subjects, including 11,188 PD patients. Meta-analysis showed that higher levels of serum triglyceride (S-TG) [standard mean different (SMD) = - 0.26 (95% confidence interval (CI): - 0.39 to - 0.13, p<0.00001), relative risk (RR) = 0.67 (95% CI: 0.60 to 0.75, p<0.00001)] could be considered as protective factors for the pathogenesis of PD. However, there was no significant association between serum high density lipoprotein cholesterol (S-HDL) and the risk of PD. Meanwhile, serum low density lipoprotein cholesterol (S-LDL) [SMD = -0.26 (95% CI: - 0.43 to - 0.07, p = 0.006), RR = 0.76 (95% CI: 0.59 to 0.97, p = 0.03)] and serum total cholesterol (S-TC) levels [SMD = -0.21 (95% CI: - 0.33 to - 0.10, p = 0.0002), RR = 0.86 (95% CI: 0.77 to 0.97, p = 0.01)] were negatively associated with PD risk.

Conclusions: This systematic review suggests that elevated serum levels of TG, LDL and TC may be protective factors for the pathogenesis of PD. Further longitudinal and well-designed prospective studies with a large sample size are needed to confirm the findings in this meta-analysis.

Keywords: Low density lipoprotein cholesterol; Meta-analysis; Parkinson’s disease; Systematic review; Total cholesterol; Triglyceride.

Fig. 1

Flow diagram of study selection for the meta-analysis

Fig. 2

Forest plots for pooled standard weighted mean difference (a) or odds ratios (b) and the corresponding 95% confidence intervals (CIs) of studies assessing the association between S-TC levels and risk of Parkinson’s disease. Forest plots pooled standard weighted mean difference (c) or odds ratios (d) for meta-analysis after excluding the study by Ikeda et al. [20] or Hu et al. [33]

Fig. 3

Forest plots for pooled standard weighted mean difference (a) or odds ratios (b) and the corresponding 95% confidence intervals (CIs) of studies assessing the association between S-TG levels and risk of Parkinson’s disease. Forest plots pooled standard weighted mean difference (c) for meta-analysis after excluding the study by Ikeda et al. [20]

Fig. 4

Sensitivity analyses for pooled standard weighted mean difference and odds ratios of studies assessing the association between S-TC levels and risk of Parkinson’s disease using a leave-one-out strategy