Assessment of autonomic nervous system functions in patients with vitamin B-12 deficiency by power spectral analysis of heart rate variability

The purpose of this study was to test the autonomic nervous system function of patients with vitamin B-12 deficiency (megaloblastic anemia) by measuri ng heart rate variability (HRV). The study population consisted of 17 vitam in B-12 deficient patients and 15 age- and sex-matched normal volunteers. H RV was measured by power spectral analysis from which power of the low freq uency (LF) peak (0.04-0.15 Hz), normalized units of the LF peak (LFNU), pow er of the high frequency (HF) peak (0.15-0.4 Hz), normalized units of the H F (HFNU), and ratio of power of LF to power of HF (LF:NF) were calculated V itamin B-12 deficient patients had lon er LF, LFNU, HF, HFNU, and LF:HF rat io than normal volunteers (P < 0.05). Decreases in sympathetic indices (LF and LFNU) were greater than those measured in parasympathetic indices (HF a nd HFNU). All HRV parameters correlated positively with the level of vitami n B-12 (P < 0. 001) and negatively with the duration of disease (P < 0. 001 ). After vitamin B-12 replacement the HRV parameters of pa tien ts and cont rols became comparable (P > 0.05). Our data suggest that autonomic sympathe tic and parasympathetic nervous activities are decreased in patients with v itamin B-12 deficiency, an abnormality that can be corrected by vitamin B-1 2 replacement therapy.