Cardiovascular autonomic reflex tests using a handheld device in the diagnosis of cardiovascular autonomic neuropathy in patients with schizophrenia

Study objective
This study investigated whether schizophrenia and the duration of schizophrenia were associated with cardiovascular autonomic neuropathy (CAN) by using heart rate variability (HRV) as a marker.

Design
Cross-sectional study.

Setting
The examinations were conducted at the Centre for Psychosis Research and at the Department of Cardiology, Aalborg University Hospital, Aalborg, Denmark.

Participants
240 patients with first-episode and chronic schizophrenia and 180 controls.

Interventions
CAN was assessed by the cardiovascular reflex tests (CARTs): HR, RS ratio, E:I ratio, and VM using a handheld device.

Main outcome measures
One abnormal CART was interpreted as borderline CAN and ≥2 abnormal CARTs established definitive CAN. Borderline CAN and definitive CAN together was categorized as overall CAN. Analyses were adjusted for age, sex, smoking, overweight, and hypercholesterolemia.

Results
A total of 240 patients with schizophrenia (median age 42.5 [28.8, 52.3], 42.9 % women) and 180 controls (median age 45.8 [24.0, 60.1], 47.8 % women) were included, with 50.8 % of patients with schizophrenia having overall CAN compared to 27.2 % among controls. Dividing patients into patients with first-episode and chronic schizophrenia, 32.9 % vs 10 % (p < 0.001) and 59.1 % vs 41 % (p < 0.001) had overall CAN compared with controls, respectively. Schizophrenia was significantly associated with overall CAN (OR, 2.80; 95%CI, 1.75–4.50), with an OR of 2.31 (95%CI, 1.14–4.68) for first-episode schizophrenia and an OR of 2.97 (95%CI, 1.81–4.87) for chronic schizophrenia.

Conclusion
It was demonstrated that a diagnosis of schizophrenia was associated with CAN. Patients with chronic schizophrenia had a significantly higher prevalence of CAN compared to patients with first-episode schizophrenia, suggesting an association between the duration of schizophrenia and CAN.