Vitamin B12 supplementation improves heart rate variability in healthy elderly Indian subjects

While vitamin B12 deficiency is global, data in elderly Indians are lacking. The problem in India is likely to be higher because of vegetarianism and malabsorption related to gastro-intestinal parasites. Autonomic dysfunction is known to occur much earlier in pernicious anemia. However, what is not known is whether these changes are reflected in healthy elderly individuals. This study assessed cardiac sympathetic and parasympathetic activity using heart rate variability (HRV) in healthy elderly individuals of low and high vitamin B12 status and evaluated the effect of vitamin B12 supplementation in those with low vitamin B12 status. 140 elderly subjects aged ≥60 years were screened; 47 healthy subjects were assessed. They underwent blood sampling, anthropometry, HRV and nerve conduction assessment. Subjects were classified based on vitamin B12 level (148 pmol/L) into deplete vitamin B12 and replete vitamin B12 groups. Elderly subjects with low vitamin B12 status underwent cyanocobalamin supplementation (100 μg) for 3 months. Low frequency (LF) HRV in absolute units was significantly lower in the low vitamin B12 group. Following supplementation, LF HRV in absolute units and total power rose significantly as compared to pre-supplementation values for the entire supplemented group. In conclusion, elderly with lower vitamin B12 status have reduced low frequency HRV suggestive of sympathetic involvement. Supplementation with vitamin B12 for 3 months results in a significant increase in low frequency HRV to values comparable with unsupplemented, but vitamin B12 replete elderly.