***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: OBJECTIVE Individual differences in sensitivity to cyclical changes in ovarian steroids estradiol ( E2 ) and progesterone ( P4 ) have been implicated in the pathophysiology of menstrually related mood disorder ( MRMD ) . However , no prospect i ve studies have investigated psychosocial risk factors for sensitivity to hormone effects on mood in MRMD . Using a repeated measures approach and multilevel models , we tested the hypothesis that a history of abuse provides a context in which within-person elevations of E2 and P4 prospect ively predict daily symptoms . METHOD 66 women with prospect ively-confirmed MRMD recruited for a trial of oral contraceptives provided  1 month of baseline hormone and mood data prior to r and omization . Lifetime physical and sexual abuse experiences were assessed . Across one cycle , women completed daily measures of symptoms and provided blood sample s on 5 days across the menstrual cycle . Current E2 and P4 were centered within person ( CWP ) such that higher values represented cyclical elevations in hormones . RESULTS Rates of physical ( 27 % ) and sexual ( 29 % ) abuse were high , consistent with previous work documenting a link between trauma and MRMD . In women with a history of physical abuse , cyclical increases in P4 predicted greater mood and interpersonal symptoms on the three days following that sample . In women with a history of sexual abuse , cyclical increases in E2 predicted greater anxiety symptoms on the three days following that sample . CONCLUSIONS Results inform further inquiry into the role of severe life stressors and stress response systems in MRMD . We discuss areas for future research on the psychosocial and physiological pathways through which abuse may influence the link between hormones and symptoms The objective of this study was to evaluate whether heart rate variability ( HRV ) can be used as an index of parasympathetic reactivation after exercise . Heart rate recovery after exercise has recently been shown to have prognostic significance and has been postulated to be related to abnormal recovery of parasympathetic tone . Ten normal subjects [ 5 men and 5 women ; age 33 + /- 5 yr ( mean + /- SE ) ] exercised to their maximum capacity , and 12 subjects ( 10 men and 2 women ; age 61 + /- 10 yr ) with coronary artery disease  exercised for 16 min on two separate occasions , once in the absence of atropine and once with atropine ( 0.04 mg/kg ) administered during exercise . The root mean square residual ( RMS ) , which measures the deviation of the R-R intervals from a straight line , as well as the st and ard deviation ( SD ) and the root mean square successive difference of the R-R intervals ( MSSD ) , were measured on successive 15- , 30- , and 60-s segments of a 5-min ECG obtained immediately after exercise . In recovery , the R-R interval was shorter with atropine ( P < 0.0001 ) . Without atropine , HRV , as measured by the MSSD and RMS , increased early in recovery from 4.1 + /- 0.4 and 3.7 + /- 0.4 ms in the first 15 s to 7.2 + /- 1.0 and 7.4 + /- 0.9 ms after 1 min , respectively ( P < 0.0001 ) . RMS ( range 1.7 - 2.1 ms ) and MSSD were less with atropine ( P < 0.0001 ) . RMS remained flat throughout recovery , whereas MSSD showed some decline over time from 3.0 to 2.2 ms ( P < 0.002 ) . RMS and MSSD were both directly related ( r(2 ) = 0.47 and 0.56 , respectively ; P < 0.0001 ) to parasympathetic effect , defined as the difference in R-R interval without and with atropine . In conclusion , RMS and MSSD are parameters of HRV that can be used in the postexercise recovery period as indexes of parasympathetic reactivation after exercise . These tools may improve our underst and ing of parasympathetic reactivation after exercise and the prognostic significance of heart rate recovery Estrogens are involved in the modulation of the cardiovascular system , yet their effects in young women remains largely unknown . Women who undergo ovulation induction treatments attain extremely high estrogen concentrations during a very short time period . The aim of the present study was to evaluate the effects of an acute increase in estrogens on the autonomic nervous system modulation of heart rate variability ( HRV ) .  A total of 27 women undergoing ovulation induction and 14 normally menstruating women were prospect ively studied .  HRV was assessed during nadir and peak estrogen using time domain and power spectral density analyses . A significant increase in high-frequency spectral power ( 243 ± 77 vs. 188 ± 73 ms2/Hz , P < 0.01 ) with a significant decrease in the ratio of low to high-frequency power was observed during estrogen peak in women undergoing induction of ovulation . The acute increase in estrogen in women undergoing ovulation induction was associated with vagal activation and altered sympathovagal balance Measuring heart rate variability ( HRV ) is a way to assess the autonomic regulation of the heart . Decreased HRV , indicating reduced parasympathetic tone , has previously been found in depression and anxiety disorders . The objective of this study was to assess HRV in women with premenstrual dysphoric disorder ( PMDD ) . To this end , time domain variables and frequency domain variables were assessed in 28 women with PMDD and in 11 symptom-free controls during both the symptomatic luteal phase and the non-symptomatic follicular phase of the menstrual cycle . Two variables reflecting vagal activity in the time domain , the root mean square of differences of successive normal RR intervals ( rMSSD ) and st and ard deviation of normal RR intervals ( SDNN ) were lower in PMDD patients , but this difference was statistically significant in the follicular phase only . The most important vagal measure in the frequency domain , supine high frequency ( HF ) , also appeared lower in PMDD subjects during the follicular phase . It is suggested that PMDD may be associated with reduced vagal tone compared to controls and that this difference is most apparent in the non-symptomatic follicular phase of the menstrual cycle Background Menstrual cycle-related symptoms are an important health issue for many women , and some may affect cardiac autonomic regulation . In the present study , we evaluated the cardiovascular and physiological stress response to 12-h short-term fasting in the menstrual phases of healthy young women . Methods We performed a r and omized crossover study . Subjects were seven female university students ( age : 22.3 ± 1.0 years ) . The experiments comprised four sessions : meal intake in the follicular phase , meal intake in the luteal phase , fasting in the follicular phase , and fasting in the luteal phase . All subjects participated in a total of four experimental sessions during two successive phases ( follicular and luteal phase in the same menstrual cycle , or luteal phase and follicular phase in the next menstrual cycle ) according to a r and omized crossover design . R-R intervals were continuously recorded before and after meals , and power spectral analysis of heart rate variability was performed . Other physiological data were obtained before and 20 , 40 , 60 , and 80 min after meal intake or after the corresponding time point of meal intake ( fasting in the follicular or luteal phase ) . Results Heart rate decreased during fasting in the follicular and luteal phases . High frequency power increased during fasting in the follicular and luteal phases . In addition , salivary cortisol concentrations decreased during fasting in the luteal phase . Conclusions In the present study , short-term fasting result ed in higher parasympathetic activity and lower cortisol levels in the luteal phase in these young women . These results indicate a possibility to produce an anti-stress effect in the luteal phase , which may reduce menstrual symptoms Background Work stress is associated with an increased risk of pre-diabetes , Type 2 diabetes , and inflammation , as well as decreased autonomic nervous system function as measured , for example , via heart rate variability . We investigated the extent to which the association between work stress and glycemic status is mediated by vagally-mediated heart rate variability ( vmHRV ) and /or inflammation . Methods Cross-sectional data from the Mannheim Industrial Cohort Study ( MICS ) with 9,937 participants were analyzed . The root mean squared successive differences ( RMSSD ) from long-term heart rate monitoring during work and night time periods was used to index vmHRV . Fasting plasma glucose and glycosylated hemoglobin were assessed to determine glycemic status . High sensitive C-reactive protein levels were observed as a measure of systemic inflammation and the Effort-Reward-Imbalance scale was used to evaluate work stress . Mediation models were adjusted for age , sex , and occupational status , and estimations were bootstrapped ( 5,000 replications ) . Results Effort-Reward-Imbalance was significantly negatively associated with RMSSD and both glycosylated hemoglobin and fasting plasma glucose during both work and night time periods . Effort-Reward-Imbalance was observed to have a significant direct effect on glycosylated hemoglobin and significant indirect effects , through RMSSD , on both glycemic measures during both time periods . Introducing C-reactive protein as a further mediator to the model did not alter the indirect effects observed . C-reactive protein , as an exclusive mediator , was observed to have smaller direct and indirect effects on the glycemic measures as compared to when Effort-Reward-Imbalance was included in the model . Conclusions Our results suggest that the association between work stress and glycemic status is partially mediated through vmHRV independent of systemic inflammation as measured by C-reactive protein . We conclude that work stress may be an additional factor that promotes development of hyperglycemic-metabolic states . If supported by prospect i ve evidence , these results may lead to new approaches for primary prevention of hyperglycemia in the workplace The purpose of this study was to investigate the effects of the ovarian hormones and the use of oral contraceptive pills ( OCP ) on cardiac vagal withdrawal at the onset of dynamic exercise . Thirty physically active women aged 19–32 years were divided into two groups :  OCP users ( n = 17 ) and non-OCP users ( n = 13 ) . Participants were studied r and omly at three different phases of the menstrual cycle : early follicular ( day 3.6 ± 1.2 ; range 1–5 ) , ovulatory ( day 14.3 ± 0.8 ; range 13–16 ) and midluteal ( day 21.3 ± 0.8 ; range 20–24 ) , according to endogenous ( in non-OCP users ) or exogenous ( in OCP users ) estradiol and progesterone variations . The cardiac vagal withdrawal was represented by the cardiac vagal index ( CVI ) , which was obtained by the 4-s exercise test . Additionally , resting heart rate , systolic ( SBP ) and diastolic blood pressure ( DBP ) were obtained . The CVI was not significantly different between the three phases of the menstrual cycle in either the non-OCP users ( early follicular : 1.58 ± 0.1 ; ovulatory : 1.56 ± 0.1 ; midluteal : 1.58 ± 0.1 , P > 0.05 ) or OCP users ( early follicular : 1.47 ± 0.1 ; ovulatory : 1.49 ± 0.1 ; midluteal : 1.47 ± 0.1 , P > 0.05 ) ( mean ± SEM ) . Resting cardiovascular responses were not affected by hormonal phase or OCP use , except that the SBP was higher in the OCP users than non-OCP users in all phases of the cycle ( P < 0.05 ) . In summary , our results demonstrate that cardiac vagal withdrawal at the onset of dynamic exercise was not impacted by the menstrual cycle or OCP use in physically active women We investigated the effect of ovarian hormones and aging on breathing pattern [ pulmonary minute ventilation $ $ { \left ( { \dot {V}_{{{\rm E } } } } \right ) } $ $ ] , tidal volume ( VT ) , breathing frequency ( Fb ) , and respiratory sinus arrhythmia ( RSA ) in women . Recordings of $ $ \dot {V}_{{{\rm E}}}$$ and  electrocardiogram ( ECG )  were obtained from 23 healthy women ( 10 premenopausal , 13 postmenopausal ) under resting , isocapnic hypoxia ( IH ) , and euoxic hypercapnia ( EH ) conditions . Premenopausal women were tested on three different days , each day corresponding to a specific phase of the menstrual cycle ( follicular , mid-cycle , and luteal ) ; postmenopausal women ( PMW ) were tested on 1 day only . On each test day , subjects were challenged with IH and EH . The order of the two tests was r and omized and separated by at least 1 hour . Due to the low Fb of several PMW , the b and limits for RSA analysis had to be adjusted . The spectral coherence between respiratory flow and ECG RR-interval was used to determine the spectral b and . Within the spectral b and , there was a consistent phase relationship between the two variables where high values of spectral coherence indicate a well-defined phase relationship between respiratory flow and RR-interval variability . The main findings in this study for RSA are fourfold . First , RSA did not change with different levels of ovarian hormones ( progesterone , ser 
    Output:
    
In conclusion , meta-analyses indicate the presence of CVA fluctuations across the menstrual cycle .