***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background —High levels of phobic anxiety  have been associated with elevated risks of  coronary heart disease ( CHD ) death and sudden cardiac death ( SCD ) among men . To the best of our knowledge , no studies have looked at this association among women . Anxiety may influence CHD mortality by increasing the risk of ventricular arrhythmia and SCD . Methods and Results —We prospect ively examined the relationship between phobic anxiety , as measured by the Crown-Crisp index ( CCI ) , and CHD among women participating in the Nurses ' Health Study . Among 72 359 women with no history of cardiovascular disease or cancer in 1988 , 97 SCDs , 267 CHD deaths , and 930 nonfatal myocardial infa rct ions ( MI ) were documented over 12 years of follow-up . A higher score on the CCI was associated with an increased risk of SCD and fatal CHD but not of nonfatal MI in age-adjusted ( P , trend ≤0.008 ) and in multivariable models excluding possible biological intermediaries ( P , trend ≤0.03 ) . Multivariable adjustment appeared to attenuate the relations ; women who scored 4 or greater on the CCI were at a 1.59-fold ( 95 % CI , 0.97 to 2.60 ) marginally increased risk of SCD and a 1.31-fold ( 95 % CI , 0.97 to 1.75 ) marginally increased risk of fatal CHD compared with those who scored 0 or 1 . After control for possible intermediaries ( hypertension , diabetes , and elevated cholesterol ) , a trend toward an increased risk persisted for SCD ( P=0.06 ) . Conclusions —These prospect i ve data suggest that high levels of  phobic anxiety are associated with an increased risk of fatal CHD , particularly from SCD . Some but not all of this risk can be accounted for by CHD risk factors associated with phobic anxiety Background Antipsychotic-induced subjective inner restlessness is one of the common and distressing adverse effects associated with antipsychotics ; however , its underlying neurobiological basis is not well understood . We examined the relationship between antipsychotic-induced subjective inner restlessness and autonomic neurocardiac function . Methods Twenty-two schizophrenia patients with antipsychotic-induced subjective restlessness , 28 schizophrenia patients without antipsychotic-induced subjective restlessness , and 28 matched healthy control subjects were evaluated . Assessment s of the linear and nonlinear complexity measures of heart rate dynamics were performed . Multivariate analysis of variance and correlation analysis were conducted . Results The mean interbeat ( RR ) interval value was significantly higher in control subjects than in patients with and without antipsychotic-induced subjective restlessness ( P < 0.05 ) . The low frequency/high frequency ratio was significantly higher in patients with antipsychotic-induced subjective restlessness than in control subjects and in patients without antipsychotic-induced subjective restlessness ( P < 0.05 ) , while the approximate entropy value was significantly lower in patients with antipsychotic-induced subjective restlessness than in control subjects and in patients without antipsychotic-induced subjective restlessness ( P < 0.05 ) . Correlation analyses controlling for psychotic symptom severity showed that the degree of antipsychotic-induced restlessness had a significant negative correlation with the value of approximate entropy ( P < 0.05 ) . Conclusion The results indicate that antipsychotic-induced subjective restlessness is associated with altered heart rate dynamics parameters , particularly the nonlinear complexity measure , suggesting that it might adversely affect autonomic neurocardiac integrity . Further prospect i ve research is necessary to eluci date the precise interrelationships and causality Background — Cardiac mortality and electrophysiological dysfunction both increase with age . Heart rate variability ( HRV ) provides indices of autonomic function and electrophysiology that are associated with cardiac risk . How habitual physical activity among older adults prospect ively relates to HRV , including nonlinear indices of erratic sinus patterns , is not established . We hypothesized that increasing the levels of both total leisure-time activity and walking would be prospect ively associated with more favorable time-domain , frequency-domain , and nonlinear HRV measures in older adults . Methods and Results — We evaluated serial longitudinal measures of both physical activity and 24-hour Holter HRV over 5 years among 985 older US adults in the community-based Cardiovascular Health Study . After multivariable adjustment , greater  total leisure-time activity , walking distance , and walking pace were each prospect ively associated with specific , more favorable HRV indices , including higher 24-hour st and ard deviation of all normal-to-normal intervals ( Ptrend=0.009 , 0.02 , 0.06 , respectively ) and ultralow-frequency power ( Ptrend=0.02 , 0.008 , 0.16 , respectively ) . Greater walking pace was also associated with a higher short-term fractal scaling exponent ( Ptrend=0.003 ) and lower Poincaré ratio ( Ptrend=0.02 ) , markers of less erratic sinus patterns . Conclusions — Greater total leisure-time activity , and walking alone , as well , were prospect ively associated with more favorable and specific indices of autonomic function in older adults , including several suggestive of more normal circadian fluctuations and less erratic sinoatrial firing . Our results suggest potential mechanisms that might contribute to lower cardiovascular mortality with habitual physical activity later in life Background —The predictive value of heart rate variability ( HRV ) in chronic heart failure ( CHF ) has never been tested in a comprehensive multivariate model using short-term laboratory recordings design ed to avoid the confounding effects of respiration and behavioral factors . Methods and Results —A multivariate survival model for the identification of sudden ( presumably arrhythmic ) death was developed with data from 202 consecutive patients referred between 1991 and 1995 with moderate to severe CHF ( age 52±9 years , left ventricular ejection fraction 24±7 % , New York Heart Association class 2.3±0.7 ; the derivation sample ) .  Time- and frequency-domain HRV parameters obtained from an 8′ recording of ECG at baseline and during controlled breathing ( 12 to 15 breaths/min ) were challenged against clinical and functional parameters . This model was then vali date d in 242 consecutive patients referred between 1996 and 2001 ( validation sample ) . In the derivation sample , sudden death was independently predicted by a model that included low-frequency power ( LFP ) of HRV during controlled breathing ≤13 ms2 and left ventricular end-diastolic diameter ≥77 mm ( relative risk [ RR ] 3.7 , 95 % CI 1.5 to 9.3 , and RR 2.6 , 95 % CI 1.0 to 6.3 , respectively ) . The derivation model was also a significant predictor in the validation sample ( P = 0.04 ) . In the validation sample , LFP ≤11 ms2 during controlled breathing and ≥83 ventricular premature contractions per hour on Holter monitoring were both independent predictors of sudden death ( RR 3.0 , 95 % CI 1.2 to 7.6 , and RR 3.7 , 95 % CI 1.5 to 9.0 , respectively ) . Conclusions —Reduced short-term LFP during controlled breathing is a powerful predictor of sudden death in patients with CHF that is independent of many other variables . These results refine the identification of patients who may benefit from prophylactic implantation of a cardiac defibrillator OBJECTIVES Cardiac mortality is known to be increased in depressive patients . However , the underlying mechanisms remain elusive to date . Decreased heart rate variability ( HRV ) has been discussed as contributing to increased cardiac mortality , but studies examining patients suffering from major depressive disorder ( MDD ) have revealed inconsistent results . This study aim ed to investigate long-term and broad b and parameters of heart rate regulation in MDD , which have been shown to be more sensitive for the assessment of autonomic dysfunction . METHODS A total of 18 non-medicated patients suffering from MDD and 18 matched control subjects without cardiac disease were recruited  and 24-h ambulatory electrocardiograms were recorded . Data were recorded during three distinct time intervals linear and nonlinear parameters as well as autonomic information flow ( AIF ) were calculated . RESULTS The power law slope was significantly reduced in the patient group for all intervals investigated and correlated with symptom severity , whereas st and ard deviation of the 5-min NN intervals ( SDANN ) and area under the AIF curve ( INT(NN ) ) showed significant differences between groups in the morning hours only . Analysis of st and ard HRV parameters in the time and frequency domain revealed no significant differences between groups . CONCLUSIONS The evidence for decreased complexity of cardiac regulation in depressed patients presented here might be useful as an indicator of the increased cardiac mortality known in depression , especially since these parameters are capable of predicting cardiac mortality in other diseases . The importance of these parameters for patients at risk should be evaluated in future prospect i ve studies BACKGROUND Several studies have suggested an increased risk of fatal coronary heart disease ( CHD ) among patients with panic disorder , phobic anxiety , and other anxiety disorders . We prospect ively examined this association in the Normative Aging Study . METHODS AND RESULTS An anxiety symptoms scale was constructed out of five items from the Cornell Medical Index , which was administered to the cohort at baseline . During 32 years of follow-up , we observed 402 cases of incident coronary heart disease ( 137 cases of nonfatal myocardial infa rct ion , 134 cases of angina pectoris , and 131 cases of fatal CHD : made up of 26 cases of sudden cardiac death and 105 cases of nonsudden death ) . A nested case-control design ( involving 1869 control subjects who remained free of diagnosed CHD ) was used to assess the association between anxiety and risk of CHD . Compared with men reporting no symptoms of anxiety , men reporting two or more anxiety symptoms had elevated risks of fatal CHD ( age-adjusted odds ratio [ OR ] = 3.20 , 95 % confidence interval [ CI ] : 1.27 to 8.09 ) , and sudden death ( age-adjusted OR = 5.73 , 95 % CI : 1.26 to 26.1 ) . The multivariate OR after adjusting for a range of potential confounding variables was 1.94 ( 95 % CI : 0.70 - 5.41 ) for fatal CHD and 4.46 ( 95 % CI : 0.92 - 21.6 ) for sudden death . No excess risks were found for nonfatal myocardial infa rct ion or angina . CONCLUSIONS These data suggest an association between anxiety and fatal coronary heart disease , in particular , sudden cardiac death BACKGROUND Low heart rate variability has been implicated as a risk factor for sudden death . However , no large epidemiological studies using sudden death as an outcome event have been reported . METHODS AND RESULTS A total of 6,693 consecutive patients who underwent 24-hour ambulatory ECG  were followed up for 2 years ; of these , 245 patients died suddenly . Clinical data at the time of 24-hour ambulatory ECG were collected for all patients who died suddenly and for a r and om sample of 268 patients from the study cohort . In all patients in sinus rhythm with or without occasional supraventricular arrhythmias at the 24-hour ECG ( 193 patients who died suddenly and 230 patients from the sample ) , heart rate variability parameters were derived . Patients with low short-term RR interval variability ( mean during 24 hours of per-minute st and ard deviations [ SD ] of RR intervals < 25 msec ) had a 4.1-fold higher risk ( 95 % confidence interval [ CI ] , 2.6 , 8.1 ) for sudden death than patients with high short-term variability ( > or = 40 msec ) ; after adjustment for age , evidence of cardiac dysfunction , and history of myocardial infa rct ion , the relative risk was 2.6 ( 95 % CI , 1.4 , 5.1 ) . The crude relative risk of long-term RR interval variability ( SD during 24 hours of per-minute means of RR intervals < 8 msec ) was 4.4 ( 95 % CI , 2.6 , 7.7 ) ; after adjustment for the same risk factors , it was 2.2 ( 95 % CI , 1.2 , 4.1 ) . Patients with a minimum heart rate > or = 65 beats per minute had a double risk of sudden death compared with those with a minimum heart rate < 65 beats per minute ( adjusted relative risk , 2.1 ; 95 % CI , 1.3 , 3.6 ) . CONCLUSIONS These findings support the theory that patients with low parasympathetic activity ( low short-term RR interval variability ) have an increased risk for sudden death independent of other risk factors OBJECTIVES Alarming somatic symptoms and in particular the cardiovascular symptoms , are the characteristic features of panic attacks . Increased cardiac mortality and morbidity have been proposed in these patients . Power spectral analysis of electrocardiogram R-R intervals is known to be a particularly successful tool in the detection of autonomic instabilities in various clinical disorders . Heart rate variability ( HRV ) has been found to be the outcome of rapidly reacting cardiovascular control systems . The aim of our study is to measure very low frequency b and ( VLF ) , low frequency b and ( LF ) and high frequency b and ( HF ) components of R-R interval during orthostatic experiment in patients with panic disorder before and after treatment and compares it with healthy 
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Effect sizes remained highly significant for medication-free patients compared to controls across all disorders .
Smaller and significant reductions in HRV were observed for specific antidepressants and antipsychotics .
Combined findings confirm substantial reductions in HRV across psychiatric disorders , and these effects remained significant even in medication-free individuals .
Reductions in HRV may therefore represent a significant mechanism contributing to elevated cardiovascular risk in individuals with psychiatric disorders .