We are grateful to Professor Poulton and Dr Das for clarifying their definition of the 16189 variant. In our study we determined the allele status at position 16189 of mitochondrial DNA (mtDNA), and found no evidence of an association between the 16189C polymorphic sequence variant and late onset dementia.¹ The title of our manuscript therefore reflects our observations and does not need to be corrected. Part of the confusion seems to have arisen because of different definitions of the “16189 variant” in the literature.

The standard “Cambridge” reference mtDNA sequence^2,3 has a run of cytosine residues from nucleotide position (np) 16184 to 16193 interrupted by a thymidine residue …