NDT Advance Access originally published online on June 16, 2007
Nephrology Dialysis Transplantation 2007 22(7):2093; doi:10.1093/ndt/gfm186
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Homocysteine and reverse epidemiology
Email: eziomov{at}libero.itSir,
The paper by Suliman et al ‘The reverse epidemiology of plasma total homocysteine as mortality risk factor is related to the impact of wasting and inflammation’ [1] tries to address the very important issue of the strange opposite clinical behaviour of some well-recognized mortality risk factors [in the paper, total homocysteine (tHcy) levels] in the haemodialysis population as compared to the general population. The authors suspect that this ‘reverse relationship’ between tHcy and outcome could be due to the effect of certain confounding factors such as age, gender, GFR, plasma folate, serum cholesterol, mean arterial BP, cardiovascular disease and diabetes. The inclusion of all these parameters in the Cox proportional hazards model, either for all cause and CVD adjusted mortality, did not change the ‘reverse’ nature of the relationship, in fact not significant, between tHcy and mortality. Inclusion in the model of nutritional and inflammatory markers, was associated with a ‘normalization’ of the relationship between tHcy and mortality, and this is taken by the authors as strong support of the effect of wasting and inflammation on tHcy, when evaluating this parameter as a risk factor for morbidity and mortality in haemodialysis (HD) patients. However, this statement lacks any support, since the supposed relationship between tHcy levels and mortality after adjustment for all variables plus nutritional and inflammation markers is not statistically significant (HR of low tHcy for all cause mortality was 0.73; CI: 0.33–1.60. HR for cardiovascular mortality was 0.78; CI: 0.34–1.76). Moreover, the very wide range of CI limits indicates the extreme weakness of the suggested association. For this reason, the message of the paper, also reported in the title: ‘The reverse epidemiology of plasma total homocysteine as mortality risk factor is related to the impact of wasting and inflammation’, although theoretically plausible, is not supported by the data.
Conflict of interest statement. None declared.
Chair and Division of Nephrology
Spedali Civili and University of Brescia Brescia,
Italy
References
- Suliman M, Stenvinkel P, Qureshi AR, et al. The reverse epidemiology of plasma total homocysteine as mortality risk factor is related to the impact of wasting and inflammation. Nephrol Dial Transplant (2007) 22:209–217.
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