Article Text

Factors associated with use of slip-resistant shoes in US limited-service restaurant workers
1. Santosh K Verma1,2,
2. Theodore K Courtney1,3,
3. Helen L Corns1,
4. Yueng-Hsiang Huang4,
5. David A Lombardi1,3,
6. Wen-Ruey Chang5,
7. Melanye J Brennan1,
8. Melissa J Perry3,6
1. 1Center for Injury Epidemiology, Liberty Mutual Research Institute for Safety, Hopkinton, Massachusetts, USA
2. 2Department of Family Medicine and Community Health, University of Massachusetts Medical School, Worcester, Massachusetts, USA
3. 3Environmental and Occupational Medicine and Epidemiology Program, Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA
4. 4Center for Behavioral Sciences, Liberty Mutual Research Institute for Safety, Hopkinton, Massachusetts, USA
5. 5Center for Physical Ergonomics, Liberty Mutual Research Institute for Safety, Hopkinton, Massachusetts, USA
6. 6Department of Environmental and Occupational Health, The George Washington University, Washington, District of Columbia, USA
1. Correspondence to Santosh K Verma, Liberty Mutual Research Institute for Safety, 71 Frankland Road, Hopkinton, MA 01748, USA; santosh.verma{at}libertymutual.com

## Abstract

Objectives Slips and falls are a leading cause of injury at work. Several studies have indicated that slip-resistant shoes can reduce the risk of occupational slips and falls. Few studies, however, have examined the determinants of slip-resistant shoe use. This study examined the individual and workplace factors associated with slip-resistant shoe use.

Methods 475 workers from 36 limited-service restaurants in the USA participated in a study of workplace slipping. Demographic and job characteristic information about each participant was collected. Restaurant managers provided information on whether slip-resistant shoes were provided and paid for by the employer and whether any guidance was given regarding slip-resistant shoe use when they were not provided. Kitchen floor coefficient of friction was measured. Slip-resistant status of the shoes was determined by noting the presence of a ‘slip-resistant’ marking on the sole. Poisson regression with robust SE was used to calculate prevalence ratios.

Results 320 participants wore slip-resistant shoes (67%). In the multivariate analysis, the prevalence of slip-resistant shoe use was lowest in 15–19-year age group. Women were more likely to wear slip-resistant shoes (prevalence ratio 1.18, 95% CI 1.07 to 1.31). The prevalence of slip-resistant shoe use was lower when no guidance regarding slip-resistant shoes was given as compared to when they were provided by the employer (prevalence ratio 0.66, 95% CI 0.55 to 0.79). Education level, job tenure and the mean coefficient of friction had no significant effects on the use of slip-resistant shoes.

Conclusion Provision of slip-resistant shoes was the strongest predictor of their use. Given their effectiveness and low cost, employers should consider providing slip-resistant shoes at work.

• Slips
• falls
• injury
• restaurants
• slip-resistant shoes
• personal protective equipment
• safety
• gender
• database
• biostatistics
• fracture
• methods
• surveillance
• international
• occupational

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## Introduction

Falls lead to a significant injury burden both at work and in the general population.1 The proportion of same-level slip-, trip- and fall-related occupational injuries ranges from 20% to 25% of all disabling occupational injuries in developed countries.2–5 A report from the US Bureau of Labor Statistics projected a significant increase from 2004 to 2014 in the number of injuries due to falls and a decrease in the number of injuries from bodily exertion and reaction and contact with objects, the other two major causes of occupational injuries.6 According to the Liberty Mutual Workplace Safety Index, the direct cost of same-level fall-related injuries in the USA in the year 2008 was US$8.4 billion, and the inflation-adjusted cost of injuries at work due to same-level falls increased by 42% from 1998 to 2008, the greatest increase among major leading workplace injury causes.7 Older adults are at an increased risk of injuries, particularly fractures, due to falls on the same level.3 8 Since the population is ageing in the USA and other industrialised countries and the proportion of older adults in the workforce is increasing,9 the incidence of injuries from slips and falls may continue to increase in the future. Slipping is a primary initiating event for same-level falls and contributes to between 40% and 85% of fall-related occupational injuries.5 10–12 In addition, slipping that does not result in a fall can still result in an injury from striking an object or from a muscular strain.13 14 Hayes-Lundy et al15 reported that 11% of grease burns in fast-food restaurants could be attributed to slips. The role of friction is crucial in understanding the causation of slips.16 When the available friction at the floor surface/shoe sole interface is not able to counteract shear forces generated by a foot during walking, a slip is likely to occur.17 The available friction at the floor surface/shoe sole interface depends on the floor surface characteristics, any contamination at the floor surface and shoe sole characteristics. Different shoe sole materials and tread patterns have different slip-resistant properties,18 and slip resistance can vary widely among common footwear materials.19 The UK Health and Safety Laboratory recently published a report on the slip potential of common ‘occupational footwear’ based on ramp tests in the laboratory environment.20 They reported that among shoes marketed as ‘slip-resistant’, 33% posed low, 33% posed moderate and 33% posed high slip potential on quarry tiles, a common type of floor surface, with glycerol contamination. They also found that almost all shoes that are not marketed as slip-resistant posed high slip potential in this environment. Bell et al21 reported an effective slip, trip and fall prevention intervention program for hospital employees where slip-resistant shoes were a part of the comprehensive approach. Verma et al22 conducted a prospective cohort study in limited-service restaurant workers and found that slip-resistant shoes were associated with a more than 50% reduction in the self-reported rate of slipping. They further reported that slip-resistant shoes reduced the effects of rushing and walking on a contaminated floor on the risk of slipping and suggested that slip-resistant shoes may have a substantial potential for slip and fall prevention.23 Given the potential of slip-resistant shoes in preventing slips and falls, this study examined the individual and workplace factors associated with slip-resistant shoe use in limited-service restaurant workers. ## Methods This study was conducted in 36 limited-service restaurants (establishments with North American Industry Classification System Code 72221) in the states of Connecticut, Massachusetts, New York, Pennsylvania, Tennessee and Wisconsin in the USA. These restaurants belonged to three major chains and had similar main menu items. Several approaches were used to recruit the restaurants for the study. These included approaching chains, stores, or franchisees that had previously been receptive to research studies by the investigative team members; approaching restaurant trade associations; direct solicitation of stores or franchisees and outreach via the loss control department of a large worker's compensation insurance company. A total of 475 workers were recruited from these restaurants in the years 2007 and 2008. The study was approved by the institutional review board of the Liberty Mutual Research Institute for Safety and the Office of Human Research Administration at the Harvard School of Public Health. ### Enrolment procedure Once permission to enrol a restaurant was received, members of the study team met onsite with the restaurant manager to explain the research study, administer a baseline manager survey and set up an appointment to enrol and survey the restaurant's employees. Restaurant managers were given fliers advertising the study with the date of the survey team's upcoming visit to post in their employee break area. On the scheduled date, informed consents were obtained, participants were enrolled and surveys were conducted in the restaurant. Restaurant workers not working on the day of enrolment were encouraged to come to the restaurant sometime during that day, with their work shoes, if they were interested in participating in the study. The survey materials were made available in three languages: English, Spanish and Portuguese. Enrolment procedures have been previously described in detail.22 24 ### Individual factors Demographic information about each participant was collected, including, age, gender, race and education. Questions about job characteristics included job tenure and number of hours worked per week. ### Workplace factors #### Coefficient of friction Coefficient of friction (COF) was measured in eight locations (Front Counter, Drive-Through, Sandwich Assembly, Fryer, Grill, Sink, Cooler/Freezer and Ice Machine) in each restaurant using a Brungraber Mark II slip metre with Neolite test liners. Three tiles were selected from each location, and two measurements were taken on each tile in the direction of traffic and parallel to the restaurant equipment.22 25 Floor COF was measured according to the F-1677-96 standard method published by the American Society for Testing and Materials,26 along with protocol refinements recommended by Chang.27 Measurement results were averaged at the restaurant level to calculate each restaurant's mean COF. #### Provision of slip-resistant shoes Restaurant managers provided information on whether slip-resistant shoes were provided and paid for by the employer and whether any guidance or encouragement was given to employees to buy slip-resistant shoes if they were not provided by the employer. Policy regarding slip-resistant shoes was classified into three categories: (1) provided and paid by employer, (2) some guidance given but not provided and (3) no guidance given and not provided. ### Slip-resistant shoes Participants were asked to remove the right shoe for assessment. Since clear classification criteria for slip-resistant shoes could not be found in the literature, shoes were classified as slip resistant if the manufacturer claimed them to be by putting a slip-resistant label on the sole. Participants were asked how often they wore that particular pair of shoes at work. A total of 397 (94%) participants reported wearing the same pair of shoes every day at work. ### Statistical analysis Restaurants recruited in the study were clustered within chains, and workers were clustered within restaurants. To account for the clustering of participants within restaurants, a generalised estimating equation model with a compound symmetry covariance structure28 29 was used to assess the association between the individual and workplace factors and use of slip-resistant shoes. As there were three chains, two indicator variables for chains were included in the regression model to account for the clustering of restaurants within chains. Log-binomial regression failed to converge, and Poisson regression with robust SE was used to calculate prevalence ratios and their 95% CIs.30 When a continuous variable was categorised and the effects of the categorical variables were not significant at .05 level, the association between the continuous variable (without categorisation) and use of slip-resistant shoes was also explored. ## Results Table 1 presents the demographic information of the participants. The mean age of the participants was 31 years (range=15–78 years), and 24% were 19 years or younger. More than two thirds (66.1%) of the participants were female. Participants were almost equally divided among education levels of grades 0–11 (33.9%; two participants who did not provide information on their education level were included in this group), high school graduate (39.2%) or some college or higher (26.9%). The majority of participants identified themselves as ‘White not Hispanic’ (55%), and the second largest group was ‘Black not Hispanic’ (20%), followed by ‘Hispanic or Latino’ (16%) and ‘Other’ (9%). Table 1 Demographic characteristics of the participants and prevalence of slip-resistant shoe use Participants reported working an average of 34 h per week, and the mean job tenure in their restaurant location was 36 months (median=18 months). The mean COF ranged from 0.45 to 0.86 between restaurants, with an overall average of 0.67.22 Managers at six restaurants (6/36 or 17%) reported that slip-resistant shoes were provided to their employees by the employer; another 20 managers (20/36 or 56%) reported some guidance provided regarding slip-resistant shoe use and 10 managers (10/36, or 28%) did not provide any guidance. A total of 320 participants (67%) were wearing slip-resistant shoes. In the univariate analysis (table 2), use of slip-resistant shoes was significantly lower in the 15–19-year age group compared to all other age groups. Prevalence of slip-resistant shoe use increased with age until 40 to 49 years. Male gender, ‘Black’ and ‘Other’ ethnic groups (compared to ‘White not Hispanic’), part-time work and non-provision of slip-resistant shoes were significantly associated with a lower prevalence of slip-resistant shoe use. The mean COF and education level were not significantly associated with the use of slip-resistant shoes. The association between the mean COF, when tested as a continuous variable, and the use of slip-resistant shoes was not significant. Table 2 Prevalence ratios (PRs) and their 95% CIs* for the use of slip-resistant shoes (n=475) In the multivariate analysis, the slip-resistant shoe use increased with age until 40 to 49 years. As in the univariate analysis, the prevalence of slip-resistant shoe use was lowest in the 15–19 year age group. Women were 1.19 times more likely to wear slip-resistant shoes compared to men (95% CI 1.06 to 1.34). The prevalence of slip-resistant shoe use was lower in ‘Black not Hispanic’ and ‘Other’ ethnic groups than in ‘White not Hispanic’ participants, and part-time work was associated with a decreased use of slip-resistant shoes (prevalence ratio 0.80, 95% CI 0.71 to 0.91). Use of slip-resistant shoes was 34% lower when they were not provided by the employer and when no guidance was given compared to when slip-resistant shoes were provided and paid for by the employer (prevalence ratio 0.66, 95% CI 0.55 to 0.79). Education level, job tenure and the mean COF had no significant effects on the use of slip-resistant shoes. ## Discussion A significant injury burden results from slips and falls in the workplace.5 Various studies have indicated that use of slip-resistant shoes may prevent slips and falls in the workplace.18–23 To our knowledge, this is the first study to systematically examine the factors associated with the use of slip-resistant shoes. This study examined the individual and workplace factors associated with the use of slip-resistant shoes. Results from this study suggest that younger age, male gender, ‘Black’ and ‘Other’ ethnic groups, part-time work and non-provision of slip-resistant shoes were associated with a lower prevalence of slip-resistant shoe use. We found that provision of slip-resistant shoes was the strongest factor associated with their use in limited-service restaurant workers. Prevalence of slip-resistant shoe use in restaurants where they were provided was about 1.52 times higher (1/0.66; table 2) compared to restaurants where they were not provided and no guidance was given. Other studies have found similar effects of the provision of personal protective equipment (PPE) in different work settings. Mathews et al31 reported that there was at least a 40% increase in use when the PPE was always provided compared with when it was not always provided among paramedics. Strong et al32 found that the employers' provision of protective clothing and equipment largely determined the farm workers' use of PPE at work, even after controlling for other relevant factors such as training history, job task, perceived organisational barriers and negative beliefs about PPE. They further suggested that the effectiveness of other strategies to improve the farm workers' use of PPE may be limited if PPE is not provided. Verma et al22 previously reported that slip-resistant shoes were associated with a more than 50% reduction in the self-reported rate of slipping in limited-service restaurants. Leamon and Murphy,33 in a study published in 1995, reported that the incidence rate of same-level falls over a 2-year period was 4.1 per 100 full-time-equivalent restaurant employees. They further calculated that the total workers' compensation losses caused by same-level falls in restaurants resulted in an industry-wide cost of US$116 per worker, annually. Verma et al24 previously reported that participants working in restaurants where shoes were not provided by the employer reported paying a mean of US$29.26 (SD 10.82) for slip-resistant shoes. Based on these findings, even without adjusting for inflation, each pair of slip-resistant shoes would result in cost savings of about US$58 (116/2), assuming 50% reduction in injuries from same-level falls in workers' compensation cost alone. Therefore, each US$29 invested in slip-resistant shoes could lead to a return of more than US$58. A few large employers may already have realised the protective effects of slip-resistant shoes. Six of the 36 restaurants that participated in our study provided their employees with slip-resistant shoes.

In this study, use of slip-resistant shoes was lowest in the 15–19 year age group. Only a few studies have reported on the use of PPE among teenage workers. Reed et al34 reported on the minimal use of hearing and respiratory protection among adolescent farm workers in Kentucky, Iowa and Mississippi. The study by Runyan et al35 of adolescent workers in the retail and service sector found that only a small proportion of respondents who reported hazardous exposures indicated that they used PPE. Vladutiu et al36 reported that among adolescent workers who performed tasks known to be hazardous, very few actually recognised these tasks as being hazardous or dangerous. Findings from these studies suggest that (1) adolescent workers may not recognise hazardous work conditions and (2) they may be less likely to use PPE even when they are aware of hazardous exposure. Limited-service restaurants are one of the major employers of adolescent workers.37 Their injury prevention programs in general and slip-prevention programs in particular should be designed with a focus to engage adolescents and, possibly, their parents on the risks of slips and falls and the use of slip-resistant shoes.

The use of slip-resistant shoes increased with age until 40 to 49 years and then declined in those 50 years and older. The number of participants in the 50+ age group was small (n=47), and it is not clear if this is a chance finding. However, restaurant employees are on their feet, for the majority of their work time and comfort is an important issue for them, particularly for older workers. Additionally, in an earlier cross-sectional study of restaurant workers, we reported that older workers perceived the same working surfaces as less slippery than their younger colleagues, which may have implications for PPE use.38 Future studies should examine whether the prevalence of slip-resistant shoe use is indeed lower in older workers and what factors may influence shoe use by age.

Association of gender with PPE use has varied, depending on the work settings. In a study of adolescent farm workers, Reed et al34 reported that boys were more likely to use PPE than girls. McCullagh et al39 also found a higher prevalence of hearing protection use among men compared to women among farmers from Minnesota, Montana, North Dakota and South Dakota. A study of obstetric healthcare workers did not find differences in the use of PPE by gender.40 In the present study, women were more likely to wear slip-resistant shoes than men. We also observed that participants who identified themselves as ‘Black not Hispanic’ and ‘Other’ were less likely to wear slip-resistant shoes than ‘White not Hispanic’. However, no statistically significant difference was observed between ‘Hispanic’ and ‘White not Hispanic’ participants. Reasons for these findings are unclear, and future studies should examine, in more detail, gender and ethnicity preference for the use of slip-resistant shoes and whether this information could be used in injury prevention programs to increase the use of PPE in general and slip-resistant shoes in particular.

We found only one study examining the use of PPE among part-time workers.41 In the current study, similar to the findings by Meeker et al, 41 we found that full-time work was associated with a greater use of slip-resistant shoes compared to part-time work. About 40% of restaurant employees work part time, more than twice the proportion for all industries.37 In the current study sample, 51% of the participants worked 35 h or less. Our findings highlight the importance of incorporating part-time workers into occupational safety education programs.

One of the interesting findings of the study is the lack of an association between the restaurant's mean COF and the use of slip-resistant shoes. In the univariate analysis, the prevalence of slip-resistant shoe use monotonically decreased in restaurants with lower COF (not statistically significant at .05 level). While this was not sustained in the multivariate analysis, this finding may suggest that in workplaces where environmental factors are better managed, the use of PPE is also higher.

### Strengths and limitations

One of the major strengths of the study is the assignment of slip-resistant shoe use based on a direct observation by investigators, not self-reports. Therefore, it is unlikely that an observed slip-resistant shoe use status was affected by personal and workplace factors. Another strength of the study is that 36 restaurants belonging to three different chains from six different states participated. The survey material was made available in three different languages, thus increasing the generalisability of the study findings. However, since 34 of the 36 restaurants were owned by larger employers, some of the findings may not be generalisable to smaller employers. In particular, the prevalence of slip-resistant shoe use may be lower among employees working for small employers. In addition, the high baseline prevalence of slip-resistant shoes makes it more difficult to detect the effects of factors that increase their use. It is possible that there is a day-to-day or a week-to-week variability in the use of slip-resistant shoes within a particular worker; however, 94% of workers reported that the shoes observed were their ‘usual’ shoes and that they wear them every day at work.

Previous work in restaurants may have an effect on the use of slip-resistant shoes, as either slip-resistant shoes may have been provided by the previous employer or education material may have been provided. If previous work in restaurants is associated with age, it may confound the relationship between age and use of slip-resistant shoes. In this study, information on previous restaurant work experience was not collected. However, when the analysis was restricted to those with a job tenure of 1 year or more, thus lessening the effect of previous work experience, the association between age and use of slip-resistant shoes did not change significantly. Therefore, it is unlikely that the association between age and use of slip-resistant shoes can be fully explained by previous restaurant work experience.

## Conclusion

This is one of the first studies to examine the personal and workplace factors associated with slip-resistant shoe use. Findings suggest that provision of slip-resistant shoes was the strongest predictor of their use. Given the effectiveness and low cost of slip-resistant shoes, employers may consider providing them to reduce slips and falls at work. Adolescent participants were less likely to wear slip-resistant shoes compared to their older colleagues. Gender, ethnicity and weekly work hours were also associated with slip-resistant shoe use.

### What is already known on the subject

• Same-level falls lead to a significant injury burden both at work and in the general population, and slipping is a major initiating event leading to same-level falls

• A few studies have reported that slip-resistant shoes could be effective in preventing slips and injuries resulting from slips and falls

• Provision of slip-resistant shoes by the employer was the strongest predictor of their use at work

• Adolescent workers were less likely to wear slip-resistant shoes compared to their older colleagues

• Male gender and less than 36 weekly work hours were also associated with a lower prevalence of slip-resistant shoe use

## Acknowledgments

The authors would like to thank the following people who contributed to the collection of data or study administration: Jacob Banks, Christopher Brunette, Albert Chang, Niall O'Brien, Greg Schultz, Joanna Willetts, Joe Ferreira, Sandra Goncalves, Gabriela Herscovici, Patricia Boelsen and Monica Colon. The authors would also like to thank Margaret Rothwell and Diana Lees for editing and proofreading the manuscript. The authors are indebted to Raymond W. McGorry and Angela Didomenico for their constructive criticisms of earlier drafts of the manuscript.

## Footnotes

• Funding Funded by the Liberty Mutual Research Institute for Safety.

• Competing interests None.

• Ethics approval Institutional Review Board of the Liberty Mutual Research Institute for Safety and the Office of Human Research Administration at the Harvard School of Public Health.

• Provenance and peer review Not commissioned; externally peer reviewed.