Resting HR is considered as an index of cardiac autonomic function and predictor of CVDs and mortality 
. The present study showed a significant escalation of HR in IFG group similar to a population-based study in Taiwan 
. Elevated HR may indicate sympathetic over activity or decreased cardiovagal tone. The significant rise in LFnu indicating increased sympathetic activity is not substantiated by the insignificant results observed in LF, diastolic BP and IHG test. The rise in LFnu can be relative due to significant fall in HFnu which is supported by significant fall in other cardiovagal modulation parameters like ln(HF), SDNN, RMSSD, NN50 and pNN50. Also significant negative correlation observed between HR and cardiovagal modulation parameters (HF and RMSSD) favors the argument that the increase in HR is primarily due to fall in parasympathetic tone in IFG compared to NFG group and this is consistent with the findings from previous study 
. Lower HRFTB
observed in IFG group compared to NFG group in our study indicates reduced PSNS activity and this goes in hand with previous study of Wu et al 
. Our findings support the concept that PSNS dysfunction occurs earlier in the course of development of autonomic neuropathy in diabetic subjects 
The balance between the two limbs of autonomic nervous system plays an important role in glucose homeostasis 
. LF/HF ratio is considered as an indicator of sympathovagal balance. LF/HF ratio was positively correlated with fasting glucose and it was higher in IFG group. We observed compensatory increase in fasting plasma insulin level in response to glucose load in IFG group as compared to NFG group 
. Excess glucose load 
and insulin 
can induce ROS production and this in turn can lead to development of IR 
. Elevated IR observed in IFG group, increases their risk of conversion to diabetes 
. The findings discussed above explain that there is a continuous interplay between the altered CAF, hyperinsulinemia, IR and glucose load in which one factor perpetuates another leading to the progression of the pathophysiology of metabolic derangement in IFG subjects. In our study, we confirm this with a strong negative correlation of cardiovagal modulation parameters with insulin, IR and FPG.
The increased ROS also damages bilipid cell membrane layer by lipid peroxidation (LPO) 
. TBARS, a marker of LPO was significantly increased in IFG group. On the other hand, decrease in the antioxidant enzyme activity was observed in IFG as compared to NFG group. Our observations are consistent with the findings of previous studies where oxidative stress was found to be higher in prediabetes and diabetes than in normal subjects 
. Further we also observed that TBARS correlated indirectly with cardiovagal modulation parameters and directly with FPG, but the exact opposite was observed in the case of TAC.
Inflammatory markers like hs-CRP and TNF-α was significantly increased in IFG group in accordance with previous study 
. These findings point out that IFG is a state of subclinical inflammation. Inflammatory markers showed a negative correlation with cardiovagal modulation parameters and positive correlation with FPG.
Lipid profile parameters like TC, TG, LDL-c and the derived parameters like TG/HDL-c, non-HDL-c and AIP were significantly increased in IFG group. The increased ROS seen in IFG group would have lead to oxidation of LDL-c, which increases its availability in the circulation. But, the previous studies showed inconsistent results with respect to blood lipid parameters 
The present study exhibited elevated HR, altered CAF in IFG group indicating higher risk for development of CVDs 
. Elevated IR 
, TC, LDL-c 
, ratio of TG to HDL-c 
which are strongly associated with CVDs were observed in IFG group. Increased oxidative stress and inflammatory response in prediabetic stage predict the development of atherosclerosis and type-2 diabetes 
. All these observations show that individuals with IFG have higher risk for conversion to diabetes, development of atherosclerosis and cardiovascular diseases in future.
The waist circumference, a clinically accepted tool to assess central obesity did not differ significantly between IFG and NFG group. This may avoid its influence on CAF and metabolic syndrome components 
. Progression of age also influences CAF 
and FPG. Though gender has no effect on the prevalence of IFG 
, females as energy conservers are considered to have higher parasympathetic tone than males 
. Hence, age, gender and waist in both the groups were matched in our study. We observed significantly lower physical activity in IFG than NFG group. Although major confounding factors were minimized, we could not rule out the role of physical activity that might have influenced the derangement of CAF 
, glucose load, IR 
, oxidative stress, inflammatory response and lipid profile 
in IFG group. Recent studies have explicitly demonstrated the efficacy of lifestyle intervention on preventing type-2 diabetes in subjects with prediabetes 
The limitation of this study concerns the use of IFG alone to identify the prediabetic subjects, while the lower cut off for IFG of new criteria has increased the sensitivity comparatively to IGT. We did not measure LDL-c particle size to confirm oxidation of LDL-c. IHG test used to assess sympathetic activity is not a sensitive marker compared to an invasive procedure like muscle sympathetic nerve activity. We did not have beat to beat BP monitor to determine BP variability and baroreflex sensitivity in our subjects. Another limitation that needs to be acknowledged is the sample size of the present study, but it is a preliminary study which was initiated to sensitize the population about diabetic and prediabetic conditions. However, more studies are warranted to delineate the association between CVD risk and prediabetes with large sample size.
In conclusion, the alteration in CAF tests, level of insulin, oxidative stress, inflammatory response, lipid profile and coronary atherogenic lipid risk factors in IFG group indicate their higher risk for conversion to diabetes, development of atherosclerosis and cardiovascular diseases in future. Short-term heart rate variability analysis, a noninvasive measurement for cardiac autonomic function, can be used along with blood glucose measurement in diabetics and prediabetics to assess cardiovascular risk. It is advisable to introduce standard lifestyle modifications 
right from the stage of prediabetes for delaying the progression of prediabetes to diabetes and to reduce the incidence of CVD. This may obviate the need for expensive and complicated therapies.