At first, this new paper looked like a bit of a strange study, but do read on. By using a lot of data from over 130 countries, the Ryan et al have found a link between school uniforms and physical exercise:
…among primary school-aged children, greater gender inequalities in physical activity are observed in countries/regions where school uniforms are common. The association between school uniform policies and gender inequalities in youth physical activity is largest in high-income countries/regions.
But as always, correlation doesn’t mean a causal relationship by definition. This is something the authors also warn about in the press release:
Importantly, the results do not definitively prove that school uniforms limit children’s physical activity and the researchers stress that “causation cannot be inferred.” Previous, smaller studies however provide support for these findings, indicating that uniforms could pose a barrier. For the first time, the research examines large-scale statistical evidence to assess that claim.
So, why did the researchers examine this? Well, because previous research actually suggested a possible link – for sure for girls – and now they wanted to have more data:
Existing evidence suggests that uniforms could be a factor. Previous concerns have, for example, been raised about girls’ PE uniforms and school sports kits. A 2021 study in England found that the design of girls’ PE uniforms deterred students from participation in certain activities, while the hockey player Tess Howard proposed redesigning gendered sports uniforms for similar reasons, after analysing interview and survey data.
Children often get their exercise away from PE and sports lessons, however. “Activities like walking or cycling to school, breaktime games, and after-school outdoor play can all help young people incorporate physical activity into their daily routines,” Ryan said. “That’s why we are interested in the extent to which various elements of young people’s environments, including what they wear, encourage such behaviours.”
The study analysed existing data on the physical activity levels of nearly 1.1 million young people aged five to 17 in 135 countries and combined this with newly collected data on how common the use of school uniforms is in these countries.
In over 75% of the countries surveyed, a majority of schools required their students to wear uniforms. The study found that in these countries, physical activity participation was lower. The median proportion of all students meeting the WHO recommendations in countries where uniform-wearing was the norm was 16%; this rose to 19.5% in countries where uniforms were less common.
There was a consistent gender gap between boys’ and girls’ physical activity levels, with boys 1.5 times more likely to meet WHO recommendations across all ages. However, the gap widened from 5.5 percentage points at primary school level in non-uniform countries to a 9.8 percentage point difference in countries where uniforms were required in most schools.
The finding appears to match evidence from other studies suggesting that girls are more self-conscious about engaging in physical activity when wearing uniforms in which they do not feel comfortable. “Girls might feel less confident about doing things like cartwheels and tumbles in the playground, or riding a bike on a windy day, if they are wearing a skirt or dress,” said senior author Dr Esther van Sluijs, MRC Investigator. “Social norms and expectations tend to influence what they feel they can do in these clothes. Unfortunately, when it comes to promoting physical health, that’s a problem.”
And so, as always:
The authors of the study argue that there is now enough evidence to warrant further investigation into whether there is a causal relationship between school uniforms and lower activity levels. They also highlight the importance of regular physical activity for all young people, regardless of their gender.
Abstract of the study:
Background
: We assessed whether school uniforms are associated with population-level gender inequalities in physical activity, and whether associations differ by school level, country/region income, and assessment method.Methods
: An ecological study design was employed. We collected data about global uniform practices using an online survey. We searched for country/region-level estimates of school-aged youth meeting physical activity guidelines from international surveillance studies. Study selection was conducted in duplicate using a systematic process, and a random sample of all data was checked to ensure extraction and pooling processes were accurate. We calculated absolute and relative gender inequalities in physical activity for each country. Linear regression examined associations between country/region-level uniform practices (binary yes/no exposure variable) and country/region-level gender inequalities in physical activity guideline compliance (absolute and relative inequalities). We investigated moderation by school level, stratified analyses by income group, and repeated primary analyses using device-measured data.Results
: Pooling data from 135 countries/regions (n = 1,089,852), we found no association between population-level uniform practices and gender inequalities in physical activity across all ages (absolute: β = –0.2; 95% confidence interval (95%CI): –1.7 to 1.3, p = 0.74; relative: β = 0.1; 95%CI: –0.1 to 0.2, p = 0.51). Subgroup analysis suggested a positive association in primary school settings (absolute: β = 4.3; 95%CI: –0.0, 8.6, p = 0.05). Among high-income countries, absolute inequalities were significantly greater in countries/regions with uniform practices (N = 37) compared to those without (N = 48) (9.1 (SD: 3.6) vs 7.8 percentage points (SD: 4.3)). Repeating analyses using device-measured data (n = 32,130; N = 24) did not alter our primary finding. From initial descriptive statistics, we found that in countries/regions where a majority of schools (>50%) reportedly use uniforms, there was lower compliance with physical activity guidelines among all genders (median: 16.0%, IQR: 13.2–19.9, N = 103) compared to generally non-uniform countries/regions (median: 19.5%, IQR: 16.4–23.5, N = 32) (z = 3.04, p = 0.002). (N = countries, regions and studies represented; n = sample size or participants included).Conclusion
: School uniforms are associated with greater gender inequalities in physical activity in primary school settings and in high-income countries. Our population-level findings warrant testing using individual-level data across contexts.