Exploratory analysis of mtDNA haplogroups in two Alzheimer's longitudinal cohorts

Introduction: Inherited mitochondrial DNA (mtDNA) variants may influence Alzheimer's disease (AD) risk. Methods: We sequenced mtDNA from 146 AD and 265 cognitively normal (CN) subjects from the University of Kansas AD Center (KUADC) and assigned haplogroups. We further considered 244 AD and 242 CN AD Neuroimaging Initiative (ADNI) subjects with equivalent data. Results: Without applying multiple comparisons corrections, KUADC haplogroup J AD and CN frequencies were 16.4% versus 7.6% (P =.007), and haplogroup K AD and CN frequencies were 4.8% versus 10.2% (P =.063). ADNI haplogroup J AD and CN frequencies were 10.7% versus 7.0% (P =.20), and haplogroup K frequencies were 4.9% versus 8.7% (P =.11). For the combined 390 AD and 507 CN cases haplogroup J frequencies were 12.8% versus 7.3% (P =.006), odds ratio (OR) = 1.87, and haplogroup K frequencies were 4.9% versus 9.5% (P =.010), OR = 0.49. Associations remained significant after adjusting for apolipoprotein E, age, and sex. Conclusion: This exploratory analysis suggests inherited mtDNA variants influence AD risk.