European Journal of Cardiovascular Medicine

video gaming has grown globally over the past few decades and it is considered to be more common leisure activity among adolescents and young age group.¹Video games pave the way for harsh emotions like anger, frustration, and stress along with shorter sleep duration, excessive fatigue, and prolonged sleep onset.¹ Studies have shown a significant correlation between violent video gaming & development of aggressive behavior in adolescent.¹

Studies have shown autonomic dysfunction in Internet Gaming Disorder which   leads to sympathetic over-activity causing fluctuation in blood pressure, heart rate and pulse rate.^2,3 Impaired autonomic function may lead to various health risks like congestive heart failure, arrhythmias, depression, post cardiac transplant, susceptibility to sudden infant death syndrome and diabetic neuropathy. ⁴

Autonomic dysfunction can be detected by many invasive and non-invasive tests such as blood pressure, isometric exercise, cold pressor test, blood pressure responses to orthostatic testing and Valsalva maneuver and Ewing test score but recently, new techniques, such as evaluation of heart rate variability or microneurography, have been introduced as diagnostic tools to detect autonomic dysfunction.⁵

Heart rate variability (HRV) is a sensitive diagnostic tool which is commonly used to measure autonomic function. HRV is the amount of fluctuation in heart rate as calculated by variation in beat-to-beat interval.⁶ Decreased heart rate variability indicates autonomic imbalance and is considered as a predictor of morbidity and mortality in vulnerable individuals.⁶

Hence the aim of this review article was to explore Heart Rate Variability alterations following violent video game exposure.

Background:

Autonomic Nervous System and its control on cardiovascular system:

Autonomic Nervous system term was coined by Langley in 1898. It is made up of two subdivisions i.e. Sympathetic and Parasympathetic divisions. ANS regulates cardiovascular, respiratory, gastrointestinal, excretory, thermoregulatory and other system automatically and subconsciously.^6,7 Sympathetic division arises from cell bodies in lateral horn of spinal cord from T1 to L2. Parasympathetic division arise from cell bodies from either brain stem (cranial nerve nuclei III, VII, IX, X) or from sacral spinal cord (S2, S3, S4). Sympathetic nervous system promotes ‘fight and flight’ reaction while parasympathetic nervous system promotes ‘rest and digest’ response.⁸

Human heart has intrinsic and extrinsic neural system. The intrinsic neural network in heart consists of Sinus node (SA node), Atrioventricular node, Bundle of His and Purkinje fibers.⁹ The junctional tissues of heart generate rhythmical electrical impulses which are conducted rapidly through all chambers of heart via conducting system. SA node is a pacemaker of human heart and impulse is generated from SA node.¹⁰ It is located in the right atrium near the opening of superior vena cava. SA node is responsible for maintaining the sinus rhythm between 60 to 100 beats per minute.^11,12

The extrinsic innervation of heart is by ANS i.e sympathetic and parasympathetic division of autonomic nervous system. Vagus nerve is a parasympathetic division innervates the sino-atrial node, atrio-ventricular node and also myocardium of the heart. Sympathetic nerve stimulation accelerates the cardiac activity and parasympathetic stimulation slows down the cardiac activity. The sympathetic influence on heart rate is mediated by release of epinephrine and norepinephrine.¹³

ASSESSMENT OF AUTONOMIC FUNCTIONS:

There are various methods to assess autonomic functions such as cold pressor test, hand grip exercise, Valsalva maneuver, orthostatic challenges with active standing and passive tilt table testing, neck suction pressure carotid sinus massage and heart rate variability.¹⁴ Heart rate variability (HRV) is a sensitive diagnostic tool which is commonly used to measure autonomic function.

Heart rate variability:

Heart rate variability (HRV) is a valid and non-invasive electrocardiographic method widely used to investigate autonomic nervous system balance^15,16. Heart rate variability (HRV) reflects beat-to-beat changes in RR intervals, which are related to ongoing interplay between two arms of the autonomic nervous system. Heart rate variability is one of the indicators of many pathological conditions related to cardiovascular health.

HRV provides reliable information about the interaction of sympathetic and parasympathetic nervous system.⁷ The alterations in cardiac autonomic functions bring out the changes in the heart rate variability (HRV) indicators, an assessing tool for cardiac autonomic conditions.¹⁷

Continuously alteration and regulation of the heart rate and its rhythm is made by ANS. ECG recording is one of the most common methods for assessing the heart rate. The activation of parasympathetic nervous system results in acetylcholine release, due to which the duration between R-R interval increases and heart rate decelerate. On the contrary, Sympathetic Nervous System (SNS) increases the secretion of catecholamine by the synapses, which accelerate the heart rate and its contractility.¹⁸

In 1996, a task force composed of members of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology created the necessary guidelines for comparing different assessment models of HRV. HRV measures were divided into two broad categories: time domain and frequency domain.¹⁴

Measurement of heart rate variability:

Heart rate variability measurement may be based on a battery of simple bedside reflex tests or may implement more advanced computer-based algorithms to reflect RR interval changes. Electrocardiogram (ECG)-based evaluation of HRV may be performed by several methods, including linear methods (time- and frequency-domain analysis) as well as nonlinear techniques.¹⁸

• Linear methods:^18,19

Calculation of linear parameters, such as time-domain and frequency-domain analysis of heart rate variability (HRV), is a conventional method for assessment of autonomic nervous system activity.

1. Time domain methods: Time domain methods in a continuous ECG recording permit determination of either instant heart rate or intervals between successive normal QRS complexes. It is the simplest way to analyze HRV data and defines differences in inter-beat intervals as a mean and Standard deviation.

Parameters of time domain analysis include:

1. SDNN: The standard deviation of NN, so called normal to normal, intervals. It encompasses both long and short term variability and thus describes the overall HRV.
2. SDANN: The standard deviation of the average NN intervals calculated over successive 5 min periods of 24 hrs recording.
3. RMSDD: The square root of mean squared differences of successive NN intervals. It reflects parasympathetic activity.
4. pNN50%: The percentage of adjacent NN intervals that differ from each other by more than 50 ms and closely related to parasympathetic activity.

1. Frequency domain methods: Frequency domain describes the inter-beat intervals as a complex sum of waveforms. The variation in heart rate is distinguished in terms of the underlying rhythms that occur at different frequencies.

This includes three primary intervals:

1. High frequency Band (HF) -15-0.40 Hz corresponds to shortest cycle time 2.5-2.7 seconds. It is modulated by parasympathetic activity.
2. Low frequency band (LF) -04-0.15 Hz; cycle time 6.7-25 seconds. LF is influenced by sympathetic nervous system, parasympathetic nervous system and baro-receptor.
3. Very low frequency band (VLF) -003-0.04Hz slowest cycle of less than 25 seconds. Requires a recording period of at least 5 min but best monitored over 24 hr.
4. LF/HF: Ratio of LF/HF used as in index of sympatho-vagal balance.¹⁹

High-frequency (HF) component and a low-frequency (LF) component respectively are considered as markers of parasympathetic and sympathetic control.

Non-linear methods: Nonlinear phenomena are certainly involved in the genesis of HRV. Linear and nonlinear analysis methods were applied in the computer words inputting experiments in this study for physiological measurement.¹⁹

HRV is one of the best ways to assess the impact of various factors such as; environment, emotion, thoughts, feeling, etc., on the nervous system and how the nervous system responds accordingly.³ HRV can also suggest the fetal distress condition during labor and it is subjected to uterine contractions. As per the changes in the physiology of vital organs, the sympathetic and parasympathetic systems maintain the state of equilibrium. HRV may also give information about cycle length dependency. Whenever heart rate increases, HRV decreases because of the insufficient period for the heartbeat.³ In the geriatric group, elderly persons with cardiac diseases like ischemia and heart attack etc., or any pathological condition may result in decreased HRV at high heart rates. Significant knowledge about all the influencing factors for HRV like physiological, environmental or genetic , plays an important role not only in clinical diagnosis but also in therapeutic purpose.³

Impact of video games on ANS & Heart rate variability (HRV):

Playing video games has become a popular activity for people of all ages. There is rapid growth in development of video game industry over the last two decades. Video games have become an interactive medium and novel technology among the young generation. They have gain attention due to their effect on the central nervous system of the gamers and their ever- increasing number.¹ Excessive use of video games results in Internet gaming disorder (IGD) which is officially listed as a mental disorder in the 11^th revision of International Classification of Diseases (ICD-11) published by the WHO. Covid-19 outbreak has additionally increased the addiction to online surfing and online gaming.²

Studies have shown people exposed to violent games tend to have a more aggressive behavior, increased hostile effect and irritability as compared to people who are exposed to non - violent video games.⁶ It also shows that the autonomic imbalance in people playing video games during rest and also during game play.⁶

Autonomic responses to gaming-related cues have been assessed through HRV changes during exposure to gaming situations.¹⁶ Online gaming can trigger measurable physiological effects like pulse rate and blood pressure. Research shows that violent games elicit significantly greater sympathetic activity and higher diastolic blood pressure compared to nonviolent games. Gaming workload also appears to influence gender differences: males demonstrate higher sympathetic activity, while females show greater parasympathetic activity under higher gaming load.¹ Using a deep learning model with time–frequency HRV data, parasympathetic tone reactivity during gaming emerged as a strong predictor for classifying internet gaming disorder (IGD) severity, whereas sympathetic tone reactivity could only distinguish the severe IGD group. These findings suggest that autonomic responses to game-related cues may serve as indicators of gaming addiction status.¹

Different games  evoke different HRV responses. Action games having fast pace and high demands, are typically associated with increased sympathetic activation and reduced HRV. Horror games having unpredictability and fear-inducing stimuli, can also produce marked HRV changes, reflecting elevated anxiety and arousal.²⁰ Puzzle games generally elicit mild HRV alterations due to their lower physical and emotional demands. Intensity of game and its complexity further influence these responses—titles requiring sustained concentration, rapid decision-making, and quick motor actions tend to provoke stronger physiological arousal and more pronounced HRV changes.²⁰ Game duration is another important factor, as prolonged play can lead to cumulative physiological stress and persistent HRV alterations. Multiplayer games, especially those cantered on competition and social interaction, add another layer of modulation often increase sympathetic activity and reduce HRV.²⁰

Individual player characteristics, like level of skill, emotional state, and personality can also influence HRV responses to gaming. Highly skilled and experienced players may exhibit different HRV patterns compared to new players. Players who are already stressed or anxious may exhibit a greater decrease in HRV during gameplay. Health status, including the presence of anxiety disorders or other mental health conditions, can also influence HRV responses.²¹

The environment in which game is taking place can also modulate HRV responses. Competitive gaming, particularly in esports settings, can create a high-pressure environment and increase sympathetic activation and decreases HRV. Physical environmental factors, such as lighting and noise levels, can also affect HRV. Bright lighting and loud noise can increase arousal and lead to reduce HRV parameters.²² Study has shown that different reaction pattern, sleep pattern was observed with combination of low and high frequency in previous violent games and experimental violent and non-violent games. Study also explains that desensitization might be the possible cause for that.²³

Study conducted by Sung Jun Hong et al that  concluded that subjects with IGD showed significant reductions in parasympathetic parameter such as HF mainly during last few minutes of game ending when players requires more attention as compared to base line values. It reflect that different situations are associated with addictive pattern of gaming.²⁰

Another study conducted Jung Young Kim  on game addicted players and non -addicted players revealed that logistic regression analysis was found to be more accurate for pNNI20, RMSSD, and LF of HRV parameters in the 30 sec after the "being killed" event.²⁴

Study done by Jae Seung Chang on 22 male participants and researchers observed cardiorespiratory coupling (CRC) during video games during excessive online gaming.²⁵

Study on old people conducted by Chun-Ju Hou on Analysis of Heart Rate Variability in Response to serious games in elderly people revealed that a significant difference in the HRV parameters was observed between the two types of games i.e cognitive aptitude game and reaction time games.²⁶

Research results by Hamed Aliyari²⁷ showed correlation between salivary alpha amylase concentration and type of game played. It was found that violent games like Fear Games trigger stress which elevates salivary alpha amylase whereas it decreased significantly in non-violent video games like Puzzle games.²⁸

Various studies have provided evidences that high sympathetic nervous system increases the heart rate, decreases the heart rate variability leading to increase in mortality and morbidity from varied diseases including cardiovascular disease²⁹ Papousek³⁰ et al reported an increase in the low frequency power range (LF), a decrease in the high- frequency power range (HF), and a significant increase in the LF/HF ratio when subjects experience stress indicating enhanced sympathetic drive.

The point of convergence between exposure to violent video games and autonomic modulation, as measured through heart rate variability (HRV), highlights an important and clinically salient reflection of the neurocardiac adaptability of the human body. HRV is not only a biomarker but also a portal into the dynamic, non-linear interaction of the sympathetic and parasympathetic divisions of the autonomic nervous system. From the HRV perspective, gaming-induced physiological changes shed light on how virtual environments can temporarily but profoundly rebalance cardiovascular control mechanisms.

Evidence repeatedly indicates that violent gaming tilts autonomic balance toward sympathetic dominance, provoking stress-like cardiovascular responses, whereas extended play can paradoxically trigger parasympathetic rebound, especially in the face of fatigue. These trends are not insignificant; they reflect physiological processes involved in larger health trajectories, from cardiovascular risk stratification to neurobehavioral regulation.

Furthermore, the increasing integration of HRV measures into prognostic models of Internet Gaming Disorder (IGD) reflects not only diagnostic promise but also a critical measure for evaluating the physiological signature of excessive gaming on mental health. This renders HRV analysis a promising link between psychological constructs and measurable physiological endpoints in the era of digital media.

In summary, heart rate variability is at the intersection of neuroscience, cardiology, and behavioural psychology — providing a subtle, objective, and clinically applicable indicator of how contemporary virtual experience shapes autonomic function. As video gaming becomes increasingly integrated into daily life, its impact on human physiology requires constant examination, not only to realize its health consequences but to inform more cautious, more aware participation in interactive media

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