A systematic review and meta-analysis
de Siqueira EC, de Souza FT, Gomez RS, Gomes CC, de Souza RP. Does cell phone use increase the chances of parotid gland tumor development? A systematic review and meta-analysis. J Oral Pathol Med. 2016 Dec 9. doi: 10.1111/jop.12531. [Epub ahead of print]
BACKGROUND: Prior epidemiological studies had examined the association between cell phone use and the development of tumors in the parotid glands. However there is no consensus about the question of whether cell phone use is associated with increased risk of tumors in the parotid glands. We performed a meta-analysis to evaluate the existing literature about the mean question and to determine their statistical significance.
METHODS: Primary association studies. Papers that associated cell phone use and parotid gland tumors development were included, with no restrictions regarding publication date, language and place of publication. Systematic literature search using PubMed, Scielo and Embase followed by meta-analysis.
RESULTS AND CONCLUSION: Initial screening included 37 articles and three were included in meta-analysis. Using three independent samples including 5087 subjects from retrospective case-control studies, cell phone use seems to be associated with greater odds (1.28, 95%- confidence interval 1.09 - 1.51) to develop salivary gland tumor. Results should be read with caution due to the limited number of studies available and their retrospective design.
Salivary gland tumors are relatively rare, accounting for 2-5% of all head and neck tumors, being the parotids the most affected salivary gland (6).
We further evaluated the levels of inflammatory cytokines in the saliva produced by the parotids according to self-reported exposure to cell phone, reporting an increase in pro-inflammatory and a decrease of anti-inflammatory cytokine levels in the sample evaluated, suggesting a pro-inflammatory effect of cell phones (8).
Cell phone use was associated with greater odds (increase of 28%) of presence of tumor in the parotid glands (O.R. 1.28 95% C.I. [1.09–1.51] p = 0.0025) (Figure 2).
Primary association studies have reported discordant results (3, 5, 10, 12, 14, 15). Possible explanations for conflicting results are differences in study design, genetic background of sampled populations or clinical-epidemiological sample structure. It is important to note that discordant results do not mean that some are incorrect. Tumor manifestation is clearly a multifactorial process whose risk factors are several. Most of the studies have not assessed other risk factors when estimating existence of association.
This is the first systematic review followed by a meta-analysis to evaluate that association. Here, we report usage of cell phone increase, on average, 28% the odds of presenting parotid glands tumors.
Our results need to be read and interpreted with caution due to important limitations that need to be addressed. Although the number of subjects compiled is reasonably large, the number of independent samples is small (n = 3) and results are clearly driven by two of three studies.
Taken together, our results provide evidence of association between cell phone use and parotid tumor although their association presents mild effect.