The FIELD Study

Football’s InfluencE on Lifelong health and Dementia risk (FIELD)

BACKGROUND: In the past decade there has been growing concern around the potential increased risk of dementia through participation in contact sports.  In part, this has been driven by recognition of a specific form of a degenerative brain disease inked to traumatic brain injury (TBI), known as chronic traumatic encephalopathy (CTE), in athletes from a wide range of contact sports1 . However, despite this attention, there remains a remarkable lack of evidence regarding late health outcomes in former athletes, including risk of dementia and related diseases.

There is, therefore, a pressing need for better understanding of the influence of contact sports participation on lifelong health and wellbeing, including risk of neurodegenerative disease.

Neurodegenerative disease and sport: To date, despite increased recognition of CTE pathology in former athletes, data on the long-term neurological consequences of participation in sport are limited and conflicting.

Thus, regarding American Football, while one study reported a threefold increase in neurodegenerative mortality in a cohort of former National Football League players2, studies in former high school footballers failed to identify any increased dementia risk3. In association football, incidence of amyotrophic lateral sclerosis (ALS) has been documented as higher in former Italian professional footballers than expected from population statistics4. However, methodological limitations, including just 5 ALS cases in their study population of over 7,000 and failure to use appropriately matched population statistics, mean these data must be interpreted with caution.

Regarding late neurocognitive impact of participation in contact sport, in a study in former elite rugby players from researchers in our group, we observed mild, subclinical deficits in limited neuropsychological assessments compared to matched controls5; observations since replicated in other studies. In football, a single study reported 11% of former footballers screening positive for cognitive impairment in a self-assessment survey, in line with population expectations6. Again, however, interpretation of this study is hampered by methodological limitations, including modest recruitment numbers, selection bias in self-reporting of symptoms and failure to identify an appropriately matched community control population.

Lifelong health, wellbeing and physical activity: While the late neurological consequences of participation in sport remain uncertain, the health benefits of physical activity are long established. Specifically, regular physical activity is recognised as a benefit in both primary and secondary prevention of a range of chronic diseases7, including dementia8, and premature death7; findings promoted by Public Health England9 and reinforced in work from researchers in our group demonstrating the health benefits of regular exercise, such as active commuting10.

Regarding participation in elite level sport, evidence confirms lifelong health benefits in respect of both morbidity and mortality11,12. Indeed, whilst studies in late neurocognitive outcomes in sport provide limited insight regarding their primary aims, by contrast they provide consistent support for lifelong health benefits of sports participation. Thus, in reporting increased neurodegenerative mortality in former NFL footballers the authors also noted reduced all-cause mortality2, while our data support reduced cardiovascular disease in former rugby internationalists compared to matched controls5.

Chronic traumatic encephalopathy (CTE): The late consequences of exposure to TBI in former boxers were first described in 1928 as the punch-drunk syndrome, with the clinical features and pathology elaborated over the latter half of the 20th century as dementia pugilistica (DP)1. However,  with the first description of the stereotypical pathology of DP in a former NFL footballer in 200513 came growing recognition that this pathology might be identified in a wider range of non-boxer sports where participants are exposed to repetitive mild TBI/ concussion.

Since that first NFL case, in excess of 300 cases of a pathology now referred to as CTE have been reported from a wide and growing range of contact sports1. Regarding football, CTE pathology (then DP) was first reported in a former amateur footballer at the end of the last century14. Since then, 7 further published case descriptions of CTE pathology in former footballers have been reported, often in context of mixed neurodegenerative pathologies (e.g. with Alzheimer’s pathology also present)15. However, issues of case selection bias and reporting limitations mean the few cases so far reported provide no insight into incidence or range of dementia pathologies in former footballers, including CTE, or their clinical significance.

The FIELD Study: Given growing anxieties over perceived increased risk of dementia in former professional footballers, establishing robust data to inform on late neurodegenerative outcomes of participation in football is a priority to inform public health policy, and the sport. Importantly, however, insight into risk of neurodegenerative disease must be read in context of wider lifelong health outcomes to permit adequately informed discussions on the holistic public health implications of participation in football.

To this end, we have brought together a multidisciplinary collaboration of researchers and experts in traumatic brain injury, public health and sport to direct studies to investigate a wide range of physical and mental health outcomes, including neurodegenerative disease, in former footballers.

FIELD Study aims

FIELD Study investigators

For more information on the FIELD Study, or any of our ongoing research, please  contact us.

References:
1) Smith, DH, Johnson, VE, Stewart, W (2013). Nat Rev Neurol, 9, 211-21
2) Lehman, EJ et al (2012). Neurology, 79, 1970-1974
3) Janssen, PHH et al (2017). Mayo Clin Proc, 92, 66-71
4) Chio, A et al (2005). Brain, 128, 472-476
5) McMillan TM et al (2016). J Neurol Neurosurg Psychiatry, doi:10.1136/jnnp-2016-314279
6) Vann Jones, SA, Breakey, RW, Evans, PJ (2014). Br J Sports Med, 159-161
7) Warburton, DER, Whitney Nicol, W, Bredin, SSD (2006). CMAJ, 174, 801-809
8) Rovio, S et al (2005). Lancet Neurol, 4, 705-711
9) Public Health England (2016) http://bit.ly/2a4FStR
10) Celis-Morales, CA et al (2017). BMJ, 357, j1456
11) Teramoto, M, Bungum, TJ (2010). J Sci Med Sport, 13, 410-416
12) Lemez, S, Baker, J (2015). Sports Med Open, 1, 16 Epub
13) Omalu, BI et al (2005). Neurosurgery, 57, 128-134
14) Geddes, et al (1999). Acta Neuropathol, 98, 171-178
15) Ling, H et al (2017). Acta Neuropathol, DOI 10.1007/s00401-017-1680-3