This cross-sectional study is, to the best of our knowledge, the first to examine indoor footwear worn most of the time in the past year by a large sample representative of the Australian inpatient population. Inside the house, the categories of footwear that were worn most of the time for the past 12 months were either non-protective footwear such as slippers and thongs/flip flops, or no footwear at all, collectively representing almost 90% of the sample. Although indoor footwear is considered important in a number of health conditions, only a small proportion of people wore indoor footwear considered to be protective. We found some interesting independent associations between different indoor footwear categories (protective, non-protective and no footwear) and various sociodemographic, medical history, and foot treatment history variables, as well as further associations between these variables and individual footwear types in our sample.
Only one in nine people wore a protective indoor footwear type. Wearing such protective footwear was not independently associated with medical or foot conditions that normally require protective footwear, such as peripheral neuropathy or history of amputation. This demonstrates the disconnection between footwear recommendations and actual footwear use in these populations. This is often acknowledged clinically and has been demonstrated previously in people with a history of stroke, Parkinson’s disease  and diabetic foot ulceration . Our finding that one in nine people wear protective footwear inside the house indicates that this disconnection may be much more distinct in footwear worn inside the house than that worn outside the house with close to one in two people wearing protective footwear outside the house reported in our previous paper .
This is consistent with prior research in people at high risk of ulceration who have been found to be more likely to adhere to their prescribed bespoke shoes outside the house than inside the house . This highlights the importance of specifically inquiring about footwear habits inside the house and implementing both indoor and outdoor footwear-related preventative measures in clinical encounters with at-risk patients. This is particularly pertinent when considering some of these populations have been shown to do more weight-bearing activity indoors than they do outdoors .
Previous foot care by a specialist medical physician in the previous year was also associated with protective footwear. Yet, foot care by any other health professional (podiatrist, general practitioner, surgeon, nurse, orthotist, other) was not associated with wearing protective footwear. This was against our expectations, as we would expect footwear change interventions to be implemented successfully by most of these health professionals. This lack of association along with the high proportion of those with risk factors not wearing protective footwear inside the home, demonstrates a lack of implementation of effective footwear change interventions, particularly for footwear worn inside the house. Recently, motivational interviewing has been demonstrated to increase the adherence to therapeutic footwear in those at high risk of ulceration in the short-term . Though more research on effective strategies to reduce footwear related risk are required, it is recommended that consideration to the practicalities, purpose and social norms are considered . Further to this, wearing protective footwear was independently associated with an education level above year 10. This relationship may be mediated by the link between lower educational attainment and poorer health literacy  so this should be considered in the delivery of indoor footwear. The translatability of current footwear guidelines to clinical practice and acceptability of such footwear to patients is also a topic for further research.
The specific protective footwear types most worn were walking shoes and running shoes. Wearing walking shoes was not independently associated with any factors. However, wearing running shoes was independently associated with peripheral neuropathy, in line with recommendations for this group, but conversely running shoes were also much more likely to be worn by those without diabetes which contradicts the recommendations for this group . Furthermore, wearing running shoes was independently associated with history of stroke, whilst not going barefoot was associated with having a history of stroke which is consistent with previous research . Bowen et al.  found that following a stroke or Parkinson’s diagnosis people change their indoor footwear towards being more supportive suggesting this is for reasons of foot problems and mobility changes. However, the overall proportion of those with a history of stroke in our sample who reported wearing protective footwear most of the time inside the house in the previous year was low at only 18%. The final association found with a protective footwear type was oxford shoes being associated with being born overseas. This highlights potential cultural factors influencing footwear preferences.
Non-protective footwear was only associated with older age with odds increasing by 3% per year of age. A form of slippers (either backless slippers or standard slippers) were the most common non-protective footwear type worn in our study, but this was still a lower proportion, at 28%, than that of previous studies. Munro and Steele  found up to 38% of people over 65 living in the community wore slippers indoors, and Davis et al.  found 48% of women aged between 60 and 80 years also preferred wearing slippers indoors. This is potentially explained by our sample being more diverse in age (18–99), as slippers too were associated with age with odds increasing by 7% with each year of age and perhaps a warmer climate of Queensland Australia compared with New South Wales and Victoria where these previous studies were performed. Slippers have been found to be unsupportive, quick to lose their structural integrity and can have a lack of grip and fixation . They are therefore not recommended for populations at risk of falls or foot ulcers, although more research is needed into the types of footwear that contributes to or prevents falls .
Wearing slippers was also independently associated with other sociodemographic factors including an education level below year 10 and socio-economic status, whereas backless slippers were associated with being female. Interestingly, female gender does not appear to be as much of a predictor of indoor footwear types as it is of outdoor footwear, as identified in our previous paper . Only backless slippers and Ugg boots were independently associated with female gender in this study compared to seven types of outdoor footwear in our previous paper. This may be reflective of the more homogenous footwear types worn in the home compared to outdoors.
Thongs/flip flops were the second most common non-protective footwear type, being worn by 15% of the sample. This was similar to the 13% finding by Munro and Steele  in older people. We also found that those with a mobility impairment were less likely to wear thongs/flip flops in keeping with a finding by Bowen et al.  that people with stroke and Parkinson’s almost never wore thongs/flip flops indoors. The strongest association with wearing thongs/flip flops was living in a remote area, while smoking was also independently associated. Moccasins were also associated strongly with having seen an orthotist, age and not having a deformity. However, since < 5% of the sample wore moccasins these associations should be interpreted with caution.
The predominance of slippers and thongs/flip flops fits with what we know about considerations when purchasing indoor footwear in some specific populations such as older people and women with rheumatoid arthritis, where comfort and the convenience of not bending down to don and doff are important [3, 7]. The large proportion of people preferring to go without footwear in the home is also perhaps not surprising, especially given the warm climate of Queensland, Australia from which this sample was drawn. Further, there are sometimes cultural and religious reasons for not wearing footwear or wearing slip-on footwear in some indoor areas [3, 31]. These contextual factors should be considered when making clinical recommendations.
The factor that associated most often with indoor footwear type and category worn most in the previous year was age. In addition to the previously mentioned associations between increasing age and non-protective footwear, slippers and moccasins, older people were less likely to go barefoot and this relationship was maintained when adding socks in with barefoot in our ‘no footwear’ group. This also has implications for falls prevention as going barefoot is associated with falls in older people . The variety of relationships between footwear types and age may reflect generational preferences, or perhaps as people age and develop chronic health conditions they may value the warmth and comfort that wearing footwear such as slippers and moccasins in the home can provide compared to being barefoot. The finding that older people are more likely to wear non-protective footwear like slippers and moccasins demonstrates the need for behaviour change strategies around footwear in this population. However, the finding that older people are less likely to go without footwear is a positive starting point that may enable behaviour change interventions to more easily facilitate a move towards more protective indoor footwear.
The results of this analysis should be interpreted in the context of some strengths and limitations. The strengths of this study include that the sample was large and reported to be highly representative of an Australian inpatient population. It provides for the first time insights into the footwear habits of a large population-based sample and the sociodemographic, health and foot-related associations. The data collection instruments have demonstrated validity and reliability . However, the study is at risk of type 1 error with the volume of analyses performed, and this may account for some of the associations we identified that have seemingly no potential causal pathway or other explanation for the association; for example, not wearing socks only was associated with having depression, which does not seem to have a plausible explanation. Further, the outcome was determined through the footwear type worn most often inside the house in the previous year, which is subject to recall bias and also does not represent all indoor footwear use. Our categorisation of footwear was based on recognised guidelines [5, 13], however, there are some recommendations that were not able to be determined just from the footwear type selected. For example, the fit of the footwear on the wearer could not be assessed for appropriateness. Further, our categories of protective footwear, non-protective footwear and no footwear based on recommendations and guidelines assumes that the individual shoe was characteristic of the footwear type.