Cell Phones and Horns - Don’t Believe the Hype

The external occipital protuberance (EOP) is a normal bump found on the occipital bone on the skull. There has been a recent uptick of interest in the EOP after an article published in Nature found an increase of enlarged EOPs in younger populations. This finding has been sensationalized as being caused by prolonged phone, tablet, or computer use. Let’s take a look at the study and see what is going on.The details of the study:This was a retrospective study that included 1,200 individuals between the ages of 18 and 86 years old. The individuals were categorized according to age: 18-30 (n=300), 31-40 (n=200), 41-50 (n=200), 51-60 (n=200) and >60 (n=300).The study found that 33% of the total population had an enlarged external occipital protuberance (EEOP) defined as greater than 10 mm. The study also found that every decade increase in age group resulted in a 1.03 reduction in the likelihood of having an EEOP and that the 18-30 age group was significantly more likely to have an EEOP.The authors suggest that the increased prevalence of EEOP in the 18-30 age group was the result of repetitive loading and poor posture.Questions and concerns of the study:Before getting too deep into the logistics of the study design and statistical analysis, it is worth pointing out that half of the individuals in the 18-30 age group were asymptomatic while the rest had mild musculoskeletal pain not relating to the EOP. So while the presence of an EEOP may allow inference of the loads placed on the cervical spine, it’s relationship with cervical pain is questionable. It’s also interesting that individuals with mild musculoskeletal pain were included in the sample but those with greater pain were excluded.As a retrospective study, causation cannot be inferred. The study can point out that there is a correlation between the amount of time spent on a mobile device and the presence of EEOP. But the study is not designed to determine whether the development of EEOP was caused by the amount of time spent on a mobile device. As an example of the difference between causation and correlation, the divorce rate in Maine is correlated to the per capita consumption of margarine. However, the reduction in the divorce rate was not caused by the consumption of margarine.The study discusses how extensive use of handheld electronics and poor posture may lead to the development of an EEOP. However, the study did not measure handheld use. There is no mention of the duration of any of the individuals in this study spent on an electronic device. Were these individuals users of handheld electronics? Was there a difference in the amount of time spent on a handheld device between the age groups?While the majority of the time spent in cervical flexion may be looking at a cell phone, a better metric might be to look at the duration spent in cervical flexion. As this is the same position spent when reading a book or newspaper, writing at a desk, etc. Many electronics are only a couple of decades old at best, so younger populations are more likely to have spent more time using them than older populations which could affect the data.The EEOP count was greater in the 18-29 females, yet the article discusses that EEOP is more prevalent in male populations. The article reported that sex was the primary predictor of EEOP with males being 5.48 more likely than females. This was only true in the 40 year old age group (approximately 6% EEOP count for females and 12% EEOP count for males), with the EEOP count being similar in the 30s, 50s, and 60s.A conclusion of the study was that forward head posture was a significant component for predicting EEOP and resulted in 1.03 times increased likelihood of having an EEOP. However, females over 60 years old had the greatest amount of forward head posture yet had the same EEOP count as the males of the same age. With the large standard deviations seen on the forward head posture values, it seems unlikely that there is a statistically significant difference between groups except in the >60 year old females.While the finding of an increased prevalence of occipital exostosis in younger populations is interesting and warrants further investigation, this study does not provide “strong evidence that EEOP in the younger population is a result of increased mechanical load” and it does not support the hyperbolic statements found on several media outlets.