Assessment of salivary flow rate in the parotid gland among mobile phone users- A cross-sectional study

Introduction

A mobile phone is the most frequently used means of telecommunication and its use has become prolific across the world. Mobile phones have dragged the attention of people with day by day increase in the number of users, frequency and duration of calls per day at the hand of portable connectivity, multifunctional amenities, and its ease of use. The parotid gland has gained focus, because hand held mobile phones are usually pressed up against the side of the face in front of the ear where the gland is situated and rendering it susceptible to changes.¹

Material and methods       

The study included a total of 50 participants. The participants were selected on the basis of preformed criteria for inclusion and exclusion [Table 1]. The participants began by responding to a questionnaire regarding their mobile phone usage lifestyle. They were categorised into three groups: group 1 -case group (>2 hrs/day) included 20 patients, group 2- control group (<2 hrs/day) included 20 patients and group-3 included 10 participants who were non- mobile phone users.

Inclusion criteria

• Individuals with age limit between 18 and 30 years
• Individuals with mobile phone usage of more than 3 years
• Subjects who are mobile phone users for at least 2 hours a day

• Individuals who use their mobile phone predominantly on one side of the face

Exclusion criteria

• Individuals with history of trauma, systemic disease, salivary gland disorders, metabolic disorders
• Individuals with long-term drug history
• Individuals with adverse habits (alcohol, smoking) or drug abuse
• Individuals who use hands-face devices like microphones or Bluetooth for voice calls

Unstimulated salivary flow rate was measured from 9:00a.m. to twelve noon. Participants were instructed to avoid the consumption of any food or beverages except water (smoking, chewing gum, intake of coffee prohibited) 2 hours prior to the test session. Subjects have been told to relax for 5 minutes before calculating the flow rate. With the help of Modified Schirmer test strip unstimulated salivary flow rate was measured from the parotid glands on both sides. The basis for using unstimulated saliva rather than stimulated saliva was to evaluate the parotid glands in their resting state (the state in which the glands are for most part of the day, i.e. unstimulated).²

The Modified Schirmer test strip is a 4 cm strip made of filter paper marked in 1 mm intervals ranging from 5 to 35 mm along its length [Fig. 1]. The subjects were asked to sit upright in a dental chair and were told to swallow once to clear the salivary secretions in the mouth. The blunt rounded end of the strip was placed at the opening of the Stenson’s duct after proper isolation and held in place using a cotton plier for 1 min and the salivary flow rate was expressed in mm/1 minute. The often- preferred side of the head for mobile phone use was considered to be the dominant side and the non- dominant side on which the use was remarkably less for group 1 and 2. In case of group 3 unstimulated salivary flow rate was measured on both the side.

Statistical analysis

All data was analyzed using inferential statistics Mann-Whitney test and the analysis was carried out with SPSS17.

Results

In our study out of 40 study participants (group1 and 2), 12 (22%) used left as the dominant side for mobile phone usage and 28 (78%) used right as the dominant side for mobile phone usage.

The assessment of parotid salivary flow rate between dominant and non-dominant side resulted in a median value of 7 on both sides suggesting no significant difference [Table 2].

The participants of group 1 and 2 demonstrated salivary rate of 7 mm/min on dominant side. And

7.5 mm/min for group 1 on non-dominant side and 6.5mm/min for group 2 on non-dominant side and no significant differences were found [Table 3].

Discussion

Globally, over the past two decades, there has been a far-fetched increase in the mobile phones use which resulted in an upsurge of the exposure to electromagnetic radiations in our life.³ The parotid glands have gained interest, because they are located in front of the ear where hand held mobile phones (MPH) are usually pressed when in use. The duration and frequency of use and propinquity of mobile phones have given rise to the concerns about potential adverse effects resulting from absorption of these emissions by the tissues adjacent to the area of mobile phone handset use.²

Effects produced by the mobile phone radiation on human body can be alienated into two sections: thermal effects and non-thermal effects. Thermal effect occurs at high frequencies where the radiofrequency radiation possesses heating properties that leads to a rise in tissue or body temperature, and eventually resulting in disruption of cell function. Direct stabilizing interaction of electric field with polar molecules is the cause for nonthermal effect, with no resultant rise in temperature, leading to destruction of cell membrane integrity due to passage of eddy current formed from body absorption of radiation.³

Van Leeuwen et al. stated that even highestpowered models of mobile phones generate only 0.1degree Celsius heat. Nevertheless, unremitting use leads to a warm sensation on the skin adjacent to mobile phone users.⁴ Monfrecola et al described that the proximity of the mobile phones can alter cutaneous blood flow and increase the perfusion of skin as a consequence of radiation exposure from these devices. Thus, prolonged mobile phone use can perhaps raise skin temperature and increase tissue perfusion to decrease the elevated temperatures.⁵

Mobile phones send and obtain information by means of electromagnetic, non-ionizing radiation in the microwave range (radio-frequency [RF] waves and microwaves 800-2,200 MHz) alike to many home appliances [3].To measure the amount of electromagnetic energy exchange in biological tissues a value referred to as specific absorption rate (SAR) is calculated, which is the amount of energy absorbed per unit time per unit mass of tissue, and is expressed in W/kg. The International Commission on Non-Ionizing Radiation Protection has confined the SAR limit to 2.0 W/kg.⁶

Depending on the different type of mobile phones, the maximum local SAR values ranged between 0.2 and 1.5 W/kg on an average for 10 grams of tissue. Mobile network carrier, characteristics of mobile phone and antenna, antenna positioning, and the exuded power from the mobile phone⁷, signal strength, physical orientation to person (held to ear, use of Bluetooth devices etc.,) are the factors that determine SAR. The International Commission on Non-Ionizing Radiation Protection (ICNRP) has set frequencies up to300 GHz as limitations for exposure in many countries as their national regulations.⁸

In our study the participants of group 1 and 2 showed no significant differences in the assessment of parotid salivary flow rate between dominant and non-dominant side. In agreement with our study De Souza et al. reported that parotid salivary flow rate was not altered due to exposure parotid glands to cell phone radiations.⁹ Among the nonmobile users (group 3) the unstimulated salivary flow rate on both the sides resulted in a median value of 2.5 mm/min, which implied that the unstimulated salivary flow rate was increased in group 1 and 2 in comparison with group 3.

Goldwein and Aframian reported an increase in the capillary blood flow nearby the parotid glands which in turn leads to a rise in tissue perfusion and increase in the salivary flow rate due to continued exposure to heat which is released from mobile phone.¹⁰ Thermal effect which induces secretory parenchymal tissue expansion, with subsequent increase in parotid gland volume which can be related to an increased salivary flow rate on the dominant side of mobile phone use, is yet another possible rationale behind it.

Salivary secretion is controlled by the autonomic sympathetic and parasympathetic nervous system. Increased salivary flow rate is in concordance with the suggestion by Andrezejak et al. that mobile radiation can affect autonomic nervous system.¹¹ Contradictory results were obtained by were previously reported in the study of Singh and Pati. They found out that the participants residing near mobile towers had low salivary secretion as compared to the control group.¹²

Aydogan et al., studied the short term and long- term effect of 2100 MHz radiofrequency radiation on the parotid glands of Albino rats. The study group was exposure to cell phones for six hours/ day, for 10 or 40 days. Histopathological alterations were noticed in parotid gland both in short and long time period.¹³

Limitations of the present study was small sample size, which reduced our ability of inspiring profound assurance in the results and does not allow extrapolation to long-term effects.

Conclusion       

Recommendations are put forth to study the longterm effects to further assess and authenticate our findings and to disclose the pathophysiology underlying such changes and to eliminate the shadow of suspicion that still exists with the use of hand-held mobile phones. Even though, the mobile phone usage is fashionable and transformed the modern world ranging from basic handset to high end mobile phone it is always crucial to outweigh the risk versus benefit.