Investigating the putative unforeseen link between football fervour and colorectal cancer screening in Denmark

Introduction

Many high-income countries, including Denmark, have since 2014 implemented national and regional monitoring efforts for the early detection of colorectal cancer (CRC), as this is the 3rd most common type of cancer worldwide (Sung et al., 2021; Sinicrope, 2022; Bretthauer et al., 2022). CRC is often asymptomatic in the early stages, and mortality is high in patients with late-stage tumours. Studies show that screening can reduce incidence and mortality over time (Lauby-Secretan et al., 2018; Njor et al., 2018; Breekveldt et al., 2022; Bretthauer et al., 2022; Njor et al., 2022). Therefore, since 2014 Denmark introduced a national screening for CRC (sCRC) where all citizens in the ages between 50 to 74 were invited once between 2014 and 2017 (Larsen et al., 2018; Njor et al., 2018), and from 2018, citizens are invited every 2 years to participate by returning a stool sample, which is tested for presence of blood (Olesen et al., 2023).

In Region Zealand, Denmark, only 54% of the invited men and 63% of the women return a sample for testing. It has been observed, both in European countries (Senore et al., 2019) and at regional levels (Kirkegaard et al., 2018), that compliance with the screening program can be positively affected if sCRC is featured in the news with more citizens returning samples in the following weeks. However, despite being free of charge, social inequality in the screening program has been evident among both men and women with the association between education, and nonparticipation (Larsen et al., 2017).

Over the years, the staff responsible for the sCRC has expressed that the busyness of the recruitment for citizen participants decreased during major sporting events, despite the data showing no variation (Olesen et al., 2023). Looking at the data through the years from 2014 to 2022, several significant reductions in the percentage of participation have been clearly identified. Each of these reductions could be explained by technical or logistic reasons (e.g., transition to a new IT system or an erroneous inclusion of some citizens by the IT system). However, a significant decline in citizen participation was experienced during 2 weeks in the late autumn of 2022 that could not be justified by any previously known or well-characterised reason. Remarkably, an observation was made that the Danish Men’s Football National team participated in the Football World Cup 2022 (FWC22) in Qatar during the same exact 2-week period (Fig. 1). Therefore, we investigate the potential intersection between these two independent variables by raising the question, could a major sport event, such as FWC22, have influenced the citizens’ conscious mind to translate into a reduction of participation for the sCRC in Region Zealand, Denmark?

Methods

Results

The one-way ANOVA test revealed that the ratio of returned samples for week 44 and 45 in 2022 were highly significantly different (p < 0.0001) compared with mean values during the same 2 weeks in the previous years from 2014 to 2021 (Fig. 2 and Table S2).

In 2022, weekly mean participation in the screening program was 56.7%. The percentage of returned samples dropped significantly in week 44 and 45 to 34.2% and 41.3%, respectively. The % of participation for these 2 weeks were the lowest of the year 2022 (Fig. 3A). The RM one-way ANOVA test confirmed that reduction in week 44, 2022 was highly significantly different (p < 0.0001) to all other weeks in the same year and in previous years (2014–2022), while week 45, 2022 appeared to be significantly different (p < 0.05) to most weeks for all years from 2014 to 2022 (Figs. 3B and 3C).

One-sample T-test confirmed that response rates in week 44 and week 45 were significantly lower compared with the rest of the weeks in 2022 for both men and women (Fig. 3D).

The median return time was 31 days (median absolute deviation 14.83) in 2022. Data analysis showed that the median response time for invitations generated in week 44 was significantly longer (34.2%) than the rest of the year combined (p < 0.0001).

No other sport events resulted in a significant reduction in participation for the sCRC (Fig. S1).

Discussion

Attendance and participation in sport activities such as football, tend to unite large audiences in the enthusiasm and commitment of watching their teams compete, and are recognised to provide positive effects for participants and spectators (Doyle et al., 2016). However, there are also well-documented negative sides associated with such massive football events, in particular related to increase in alcohol consumption, domestic violence, cardiovascular events and general negligence (Wilbert-Lampen et al., 2008; Trendl, Stewart & Mullett, 2021; Forsdike, Hooker & Laslett, 2022). There is also the general view that football, as one of the most popular and widely practised sports worldwide, can somehow blur the mind of the spectator (Vallerand et al., 2008; Mansfield, Delia & Katz, 2020; Bilgiç et al., 2020), and here we hypothesise that this blurring of mind can result in delaying other priorities, such as postponing sending samples to national screening programs.

There are many factors associated with the early detection of CRC such as genetics, microbiome composition, lifestyle including diet and fitness (Garrett, 2019), but we are quite certain you may have never heard of football as being one of them. After more than 2 years of pandemic with constant global shutdowns of many international sport events, the announcement that the FWC22 would not be rescheduled and would take place despite the challenges presented, was refreshing for the many millions of enthusiastic people around the world (Dergaa et al., 2022), including football fans in Denmark with their national team qualified for this event. In fact, Denmark was ranked ninth place together with Spain in 2022 according to the FIFA’s ranking for the best teams in the world before the FWC22 in Qatar started. As such, expectations were high, and the team was domestically forecasted to go far in the tournament with an enormous national hype. Denmark is a small country with a population size at around six million, small enough for a football team to be well known and connected to the national consciousness. Football enthusiasts believed, the Danish team could reach the semi-finals and maybe even the final. Many had organized gatherings with friends, alcohol, and partying. Wretchedly, the final outcome could not be further from expectations and Denmark finished last in its group during the first round.

There are many sporting events in Denmark with great public interest and media attention. Thus, the question here is why this event may have produced an effect that could be translated into making citizens forget, not attend to, or simply delay other activities? To our knowledge and after a thorough literature review, no previous studies have considered the potential association that an international sport event, such as FWC22 could have in terms of the level of negligence in attendance or participation reduction for health screening programs.

As previously mentioned, handball for both women and men is also a very popular sport in Denmark, in particular as the men’s national team has won the World championship in 2019, 2021 and 2023. However, no reduction was detected during the weeks that these events took place, always in the month of January. Nevertheless, when comparing the time frames for the handball European championships (2014–2022), we noticed a decline during the first weeks of 2018, which partially coincided with a tournament during the same period (Fig. S1). However, similar reduction in participation has historically been observed during the last and first weeks of the year associated with the Christmas and New Years holidays. Therefore, this particular handball event association in the beginning of 2018 was ruled out, also as Denmark did not finish on the podium of finalists.

In the week, where Denmark had the first matches, only 34.2% of the recipients of invitations to sCRC have up till today returned a sample (Fig. 2A). To our surprise, the decline in participation in the sCRC was slightly more pronounced for women than for men. However, in overall, women had a higher participation in the screening program than men all year round (Fig. 3D). Roughly, 32% of the men and 38% of the women who received the invitation in the mailbox during the first week the Danish team played participated in sCRC. For the rest of the year percentages of participation were about 53.6% for men and 63% for women. Overall, the first 2 weeks of the FWC22 had significantly lower proportions of returned samples compared to the same weeks in all previous years since the screening program was initiated (Figs. 3B and 3C).

In July 2022, the Tour de France in that year edition began in Denmark with three stages, and the race even resulted with a Danish winner 23 days later. FWC22 and Tour de France probably have similar numbers of followers in Denmark; however, Tour de France did not prevent citizens from participating in the sCRC as no reduction was detected during the period of this event. In fact, during the period that Tour de France took place, the response time with citizens sending back their samples was among the lowest in 2022, meaning the citizens sent their stool samples quicker than the median time of 31 days.

We speculate that the reduction in participation for sCRC during FWC22 (compared with another major sport event, such as Tour de France) may be caused by potential differences in culture around the two events. For example, it is more common to meet up with friends and have a beer while watching a football match, than it is to do so while watching Tour de France, and possibly this social aspect pushes thoughts of returning samples further away from the minds of citizens. We encourage professionals from multidisciplinary fields across translational medicine such as social, biomedical, sports and natural science to combine efforts to help elucidate the unknown consequences of the potential intersection between football distracted enthusiasm and attendance in cancer screening programs.

Colorectal cancer screening programs worldwide are beneficial and improve the early detection of tumours and reduce mortality (Senore et al., 2019; Breekveldt et al., 2022; Bretthauer et al., 2022; Jauernik et al., 2023), and while there is some criticism about the economic cost of the different programs (Johansson, 2023), and the time they are require to run before reflecting an effective reduction in the incident and mortality (Bretthauer et al., 2022; Dominitz & Robertson, 2022), the lives of the citizens saved by these initiatives must not be measured only in currency. Therefore, expanding knowledge about external factors that may influence and reduce participation in these programs is most relevant. While sports events are documented to provide benefits to health, it is surprising that little information can be found on the association that fans’ enthusiasm can have on sCRC worldwide. The intersection of these two seemly random events, distracted football fans and a national sCRC, may have great implications for the medical translation into determining, understanding, and preventing external factors that affect the early detection of colorectal cancer and other human diseases. This may be the first study intersecting these two independent events, which is relevant as it may have potential consequences for early cancer detection.

Supplemental Information