Biochemical risk indices, including plasma homocysteine, that prospectively predict mortality in older British people: the National Diet and Nutrition Survey of People Aged 65 Years and Over.

Predictive power, for total and vascular mortality, of selected indices measured at baseline in the British National Diet and Nutrition Survey (community-living subset) of People Aged 65 Years and Over was tested. Mortality status and its primary and underlying causes were recorded for 1100 (mean age 76.7 (sd 7.5) years, 50.2% females) respondents from the baseline survey in 1994-5 until September 2008. Follow-up data analyses focussed especially on known predictors of vascular disease risk, together with intakes and status indices of selected nutrients known to affect, or to be affected by, these predictors. Total mortality was significantly predicted by hazard ratios of baseline plasma concentrations (per sd) of total homocysteine (tHcy) (95% CI) 1.19 (1.11, 1.27), pyridoxal phosphate 0.90 (0.81, 1.00), pyridoxic acid 1.10 (1.03, 1.19), alpha1-antichymotrypsin 1.21 (1.13, 1.29), fibrinogen 1.14 (1.05, 1.23), creatinine 1.20 (1.10, 1.31) and glycosylated Hb 1.23 (1.14, 1.32), and by dietary intakes of energy 0.87 (0.80, 0.96) and protein 0.86 (0.77, 0.97). Prediction patterns and significance were similar for primary-cause vascular mortality. The traditional risk predictors plasma total and HDL cholesterol were not significant mortality predictors in this age group, nor were the known tHcy-regulating nutrients, folate and vitamin B12 (intakes and status indices). Model adjustment for known risk predictors resulted in the loss of significance for some of the afore-mentioned indices; however, tHcy 1.34 (1.04, 1.73) remained a significant predictor for vascular mortality. Thus, total and primary vascular mortality is predicted by energy and protein intakes, and by biochemical indices including tHcy, independent of serum folate or vitamin B12.