Early autonomic dysfunction in patients with diabetes mellitus assessed byspectral analysis of heart rate and blood pressure variability

Patients with diabetes mellitus (DM) often have alterations of the autonomi c nervous system (ANS), even early in their disease course. Previous resear ch has not evaluated whether these changes may have consequences on adaptat ion mechanisms in DM, e.g. to mental stress. We therefore evaluated whether patients with DM who already had early alterations of the ANS reacted with an abnormal regulatory pattern to mental stress, We used the spectral anal ysis technique, known to be valuable and reliable in the investigation of d isturbances of the ANS. We investigated 34 patients with DM without clinica l evidence of ANs dysfunction (e.g. orthostatic hypotension) and 44 normal control subjects (NC group). No patients on medication known to alter ANS r esponses were accepted. The investigation consisted of a resting state eval uation and a mental stress task (BonnDet), In basal values, only the 21 pat ients with type 2 DM were different in respect to body mass index and systo lic blood pressure, In the study parameters we found significantly lower va lues in resting and mental stress spectral power of mid-frequency band (kno wn to represent predominantly sympathetic influences) and of high-frequency and respiration bands (known to represent parasympathetic influences) in p atients with DM (types 1 and 2) compared with NC group (5.3 +/- 1.2 ms(2) v s. 6.1 +/- 1.3 ms(2), and 5.5 +/- 1.6 ms(2) vs. 6.2 +/- 1.5 ms(2), and 4.6 +/- 1.7 ms(2) vs. 6.2 +/- 1.5 ms(2), for resting values respectively; 4.7 /- 1.4 ms(2) vs. 5.9 +/- 1.2 ms(2), and 4.6 +/- 1.9 ms(2) vs. 5.6 +/- 1.7 m s(2), and 3.7 +/- 2.1 ms(2) vs. 5.6 +/- 1.7 ms(2), for stress values respec tively; M/F ratio 6/26 vs. 30/14). These differences remained significant e ven when controlled for age, sex, and body weight However, patients with DM type 2 (and significantly higher body weight) showed only significant valu es in mental stress modulus values. There were no specific group effects in the patients with DM in adaptation mechanisms to mental stress compared wi th the NC group, These findings demonstrate that power spectral examination s at rest are sufficiently reliable to diagnose early alterations in ANS in patients with DM. The spectral analysis technique is sensitive and reliabl e in investigation of ANS in patients with DM Without clinically symptomati c autonomic dysfunction.