Related Experiment Video
Updated: Jul 5, 2026

Measuring Single-Cell Mitochondrial DNA Copy Number and Heteroplasmy Using Digital Droplet Polymerase Chain Reaction
Published on: July 12, 2022
Mitochondrial DNA copy number and Alzheimer's disease and Parkinson disease
Pei Qin1, Xiaojuan Chen2, Panpan Ma2
1Center for Clinical Epidemiology and Evidence-Based Medicine, Shenzhen Qianhai Shekou Free Trade Zone Hospital, Shenzhen, Guangdong, China.
Introduction:
A systematic review on the association of mitochondrial DNA copy number (mtDNA-CN) with Alzheimer's disease (AD) and Parkinson disease (PD) is lacking and the causal relationship remains unclear.
Objective:
We aimed to conduct a systematic review of observational studies on the association of mtDNA-CN with AD and PD and perform a bidirectional 2-sample Mendelian randomization (MR) study to investigate their causal relationships.
Methods:
PubMed, Embase, and Web of Science were searched for eligible studies before Jan 2025. The causal links were conducted with inverse-variance weighted (IVW) method as the main analysis.
Results:
Fourteen case-control and 2 cohort studies investigated the association between mtDNA-CN and AD, with 13 reporting decreased mtDNA-CN associated with increased risk of AD and 3 showing no significant association. All the studies (9 case-control, 1 cross-sectional, 2 cohort studies) observed the relation between mtDNA-CN and PD except for 3 studies reporting no significant association. In MR analysis, genetically predicted mtDNA-CN was not associated with AD and PD, whereas genetically predicted AD (β -0.085, 95 % CI -0.156 to -0.013; P = 0.02) but not PD was associated with mtDNA-CN. Sensitivity and replication analyses showed a stable finding.
Discussion:
The systematic review found limited observational studies on mtDNA-CN and AD and PD and majority were case-control study. Findings of the bidirectional MR study did not support a causal effect of mtDNA-CN in the development of AD and PD but found that AD can lead to decreased levels of mtDNA-CN, which suggest mtDNA-CN as a potential biomarker of AD.
Related Concept Videos
Animal Mitochondrial Genetics
Alzheimer's Disease: Overview
The clinical diagnosis of AD hinges on the presence of memory and other cognitive impairments. Biomarkers, such as changes in Aβ and tau...
Alzheimer Disease l: Introduction
Alzheimer Disease ll: Pathophysiology
Parkinson Disease ll: Pathophysiology
Dementia l: Introduction

