Risk factors for motion sickness

A variety of factors increase one’s susceptibility to and risk of developing motion sickness, some of the most common of which are:

• Gender – Women are more likely to suffer from motion sickness than men. Some experts put this down to women being of smaller stature than men, explaining that their different body shape and smaller feet lead to a reduced sense of stability which is compounded by any sort of motion, leading to further instability.
  
  Not all experts agree with this school of thought and suggest that motion sickness, which occurs as a result of the discrepancy between what a person's eyes and balance system are telling them, is linked to the increased susceptibility in women due to the fairer sex being more adept at detecting subtle visual cues than men.
  
  More recent studies have shown that genetic variants seen more commonly in women may have a significant role to play in the development of motion sickness³.

• Age – Research has shown that children younger than two years of age tend to be resistant to the symptoms of motion sickness and that the syndrome typically peaks around nine years of age and will then decrease throughout one’s adult years⁴.
• Genes – Some genetic variants have been linked to an increased risk in developing the symptoms of motion sickness. A genome-wide (a genome refers to an organism’s complete set of DNA) study³ consisting of 80,494 participants found that a total of 35 SNPs (single-nucleotide polymorphisms) were linked to motion sickness susceptibility.
  • SNPs are considered the most common form of genetic variation in people and each SNP represents a difference in a single nucleotide, which is a building block within the structure of DNA. Simply put, an SNP refers to a variation within a single nucleotide that occurs within a person’s DNA sequence.
  • The majority of the SNPs found in this study were discovered near genes that involve balance, as well as ear, eye and cranial development. These SNPs also displayed gender-specific effects with more than three times stronger effects seen in women – in which may explain why women are more susceptible to motion sickness.
• Migraine sufferers – Those who suffer from chronic migraines are thought to be more susceptible to the symptoms of motion sickness⁵. A study conducted on patients suffering from varying degrees of tensions headaches and migraines found that 50% of the migraine sufferers reported that they had a history of battling with motion sickness, compared to 20% of the patients from the tension headache group ⁶. Women are also more likely to suffer migraines than men.
• Hormonal factors – There are certain hormonal factors that may increase a person’s susceptibility to motion sickness. It is thought that pregnant women are more prone to motion sickness, in addition, the hormonal changes that take place throughout a woman’s menstrual cycle and the use of oral contraceptives such as birth control pills may also affect susceptibility.
• Expectations – Experts believe that an individual’s expectations regarding whether they may or may not become ill are also a risk factor in the development of motion sickness. An example of this was demonstrated in a controlled trial⁷ which found that a group of navel cadets (i.e. a young man training to serve as a shipman in the US Navy), who were informed that they were not likely to suffer from seasickness during their training showed lower rates of motion sickness development.

Environmental risk factors in the development of motion sickness

• Motion type – As previously mentioned, certain -frequency motions and directions are thought to be more likely in inducing motion sickness. A study⁸ that involved air travellers, found that the magnitude of low-frequency vertical and lateral motion was linked to the development of motion sickness and the symptoms associated with the condition.
• Body position – The susceptibility to motion sickness may be decreased when lying flat on one’s back. These findings were discovered through a study⁹ involving 260 passengers travelling via ship and showed that lying in the supine position will decrease a passenger’s chances of motion sickness.
  
  
  
  

^References:

^{3. NCBI. 2015. Genetic variants associated with motion sickness point to roles for inner ear development, neurological processes and glucose homeostasis. Available: https://www.ncbi.nlm.nih.gov/pubmed?term=25628336 [Accessed 16 May 2018]}

^{4. NCBI. 2016. Motion sickness. Available: https://www.ncbi.nlm.nih.gov/pubmed?term=27638085 [Accessed 16 May 2018]}

^{5. NCBI. 2005. Triggers of motion sickness in migraine sufferers. Available: https://www.ncbi.nlm.nih.gov/pubmed?term=15953297 [Accessed 16 May 2018]}

^{6. NCBI. 1984. Neuro-otological manifestations of migraine. Available: https://www.ncbi.nlm.nih.gov/pubmed?term=6334543 [Accessed 16 May 2018]}

^{7. NCBI. 1995. Seasickness as a self-fulfilling prophecy: raising self-efficacy to boost performance at sea. Available: https://www.ncbi.nlm.nih.gov/pubmed?term=7592232 [Accessed 16 May 2018]}

^{8. NCBI. 1984. Neuro-otological manifestations of migraine. Available: https://www.ncbi.nlm.nih.gov/pubmed?term=6334543 [Accessed 16 May 2018]}

^{9. NCBI. 1995. Seasickness as a self-fulfilling prophecy: raising self-efficacy to boost performance at sea. Available: https://www.ncbi.nlm.nih.gov/pubmed?term=7592232 [Accessed 16 May 2018]}