significance attributed to the J haplogroup in longevity, it would be of great interest to re-examine the individuals used in the study by De Benedictis et al. and establish whether they have this mutation. The importance of the overlap between the two mutations defining the haplogroup J (Tanaka et al., 2003) reported in mtDNA polymorphism at nucleotide position 12308 to be at a significantly increased frequency within a sample of Japanese centenarians compared to a control group aged 63 years old. The frequency was reported at 3% in centenarians and 0.4% in the control samples. This polymorphism was not observed in any of the samples of the Irish population examined here but was observed at a frequency of 1.5% in a cohort of Asian samples included in this study. The Irish population is a relatively closed population and therefore does not display the genotypical diversity that is expressed globally. This polymorphism is linked to the Asian haplogroup J and results in the absence of an Alu restriction site and has not yet been reported in the European population (Torroni et al., 1994). It is therefore understandable that this polymorphism associated with the Japanese population is not found within the Irish examined. It has been postulated that A12308G genotype decelerates the accumulation of mtDNA mutations in somatic cells with advancing age (Tanaka et al., 2003). It is further postulated that this genotype is likely to confer resistance to adult-onset diseases by suppressing obesity and atherosclerosis. The frequency of this polymorphism within the Japanese younger population may be relevant to the fact that life expectancy in Japan is one of the highest in the world. It would be of interest to investigate the frequency of this polymorphism in other Oriental populations with lower life expectancies. Our data, however, rules out a role for this polymorphism in successful ageing in the Irish Caucasian population. The A12308G polymorphism was observed at a frequency of 4% in the French study of centenarians and was at 3% in a control group of 78 adults (Ivanova et al., 1998). In this study, the polymorphism was observed to have a frequency of 2.5% in the control group samples and 1% in the aged group samples. These results would suggest that the polymorphic nucleotide may be associated with successful ageing but is not a major factor in the ageing process and would therefore not be a good predictive marker for successful ageing. It should be noted that no strong correlation between this polymorphism and any of the groups of related haplotypes displaying frequency differences between the two age groups was observed. Of the eight positive samples for this polymorphism, seven occurred in haplogroup J (containing all five control cases) and one occurred in haplogroup K (in sample <(cid:6)(cid:10)(cid:15),>(cid:28) in centenarians), indicating that the specific genetic background can affect longevity, possibly by conferring increased resistance to the accumulation of mtDNA mutations with age. Similarly, it is important to point out that any specific nucleotide or haplogroup defining a polymorphism associated with ageing may not be directly involved but simply act as a marker for other tightly linked polymorphisms occurring elsewhere in the mtDNA genome that directly affect longevity. Certainly, if the significant association of the J haplogroup with ageing is confirmed in the exact nucleotide sequence, differences responsible, and determine their functional impact on the ageing process. Our findings ofWane Peef age-associated 1 mtDNA variants in the Irish population. 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