Prevalence and correlates of foot pain in a population-based study: the North West Adelaide health study

Foot pain has long been recognised as highly prevalent in older people, affecting approximately one in three people aged over 65 years [1–3]. In older people, foot pain is associated with decreased ability to undertake activities of daily living, problems with balance and gait, and an increased risk of falls [4–6]. The prevalence of foot pain in other age-groups, however, has not been as widely studied. The 1990 US National Health Interview Survey of 119,631 people aged over 18 years included a podiatry supplement and found that 24% of the sample reported foot "trouble" [7]. More recently, a random community-based sample of 3,417 people drawn from a general practice register in the UK found that 10% of study participants aged 18 to 80 years had "disabling" foot pain [8], and a community-based postal survey of 16,222 people aged over 55 years found that 18% reported joint pain, swelling and/or stiffness in their feet [9].

Although several studies in relatively small samples of older people have been undertaken [3, 10, 11], the prevalence of foot pain in the general Australian population has never been thoroughly examined. Therefore, the aims of our study were to determine the prevalence of foot pain in a population-based sample, to explore associations between age, sex, major medical conditions, other chronic joint symptoms and foot pain, and to assess the impact of foot pain on health-related quality of life.

Our study provides the first population-based estimates of foot pain in Australia. The findings indicate that approximately one in five people report foot pain, aching or stiffness, with a higher prevalence observed in females, those aged 50 years and over and those classified as obese. However, even in patients aged under the age of 45 years old, at least 10% reported foot pain.

The overall prevalence rate reported in this study is higher than that reported in the Cheshire Foot Pain and Disability Survey in the UK (10%) [8], but lower than that reported in the US National Health Interview Survey (24%) [7] and the Framingham Foot Study (28%) [15]. These differences can be attributed to variations in the definitions of foot pain used in each study. The Cheshire survey used the case definition of the Manchester Foot Pain and Disability Index (MFPDI), which requires participants to have current foot pain, pain lasting at least one month, as well as recording at least one disability item on the questionnaire [16]. As such, the MFPDI probably identifies more severe levels of foot pain than the question we used. In contrast, the US National Health Interview Survey recorded a wide range of foot conditions under the heading of foot "trouble" (including corns and calluses), some of which may not have been symptomatic [7]. The Framingham Foot Study required participants to have pain on "most days" [15].

The associations reported between foot pain and age, female sex and obesity are largely consistent with previous reports. Prevalence studies involving participants across a wide age range have consistently found that older people have much higher rates of foot problems [7, 8, 17], which has been attributed to the cumulative effects of ageing on the integumentary, vascular and musculoskeletal structures of the foot. Similarly, several studies have found that women have a higher prevalence of foot pain than men [8, 11, 18, 19]. This has been attributed to the wearing of shoes with an elevated heel and narrow toe box, which has been shown to be associated with the development of corns, lesser toe deformities and hallux valgus (bunions) [20]. However, the higher prevalence of foot pain may also reflect sex differences in pain tolerance in general, as women are more likely to report musculoskeletal pain and pain interference at other body regions [21]. The association between foot pain and obesity can be partly explained by the significant increase in forces under the foot when walking in those who are obese [22] and the increased tendency for obese people to be flatfooted. Indeed, a recent case-control study indicated that those with chronic heel pain were three times more likely to be obese and four times more likely to have flat feet [23].

Although there was an increased prevalence of foot pain amongst those with self-reported diabetes, cardiovascular disease and osteoporosis, this did not reach significance following adjustment for age and sex. Previous studies have shown that foot problems are more common in older people with multiple chronic diseases [19, 24, 25], however in younger people foot pain is more likely to be related to overuse musculoskeletal conditions associated with physical activity (eg: plantar fasciitis) [7]. Indeed, although a strong linear relationship between foot pain and increased age was observed, this association was revealed to be considerably more complex when foot pain was stratified according to location. While pain in the toes and forefoot generally increased with age, pain in the arch and heel decreased with age, pain in the hindfoot region demonstrated a U-shaped relationship with age, and pain in the ball of the foot was similar across all age-groups. As no clinical assessments were undertaken to ascertain the underlying cause of the pain, the reasons for these variable patterns are uncertain. However, it could be speculated that foot pain in younger age-groups is more likely to be musculoskeletal in origin, whereas foot pain in older people is more likely to be caused by toe deformities, corns and calluses.

Irrespective of the underlying cause, our results indicate that foot pain has a significant impact on health-related quality of life. Participants who reported foot pain demonstrated lower scores on the SF-36, and this association persisted after adjusting for age, sex and BMI. Although significant associations between the presence of foot problems, self-reported disability [26] and inability to perform activities of daily living [4, 18, 19] have been reported in older people, the association reported between foot pain and reduced health-related quality of life across such a broad age range is a novel finding. Of particular interest, those with foot pain demonstrated lower scores for not only the physical and bodily pain components of the SF-36, but also the social functioning and mental health components. This finding suggests that the impact of foot pain extends beyond localised pain and encompasses much broader aspects of health-related quality of life.

The major strength of this study is the use of a population-based sample with excellent response rates over a broad age range. However, it is acknowledged that the study has several limitations. Firstly, we defined foot pain according to a single question rather than using foot-specific questionnaires, such as the Manchester Foot Pain and Disability Index [3, 16] or Foot Health Status Questionnaire [27]. Secondly, we were unable to examine the participants' feet in the study. We asked participants to indicate on a diagram (see Figure 1) the location of the foot pain, but did not ask which specific types of foot problem each participant had, or undertake any measurements of foot deformity. However, studies conducted in older people have indicated that only a small proportion of clinically-determined foot problems are reported as symptomatic [15, 28, 29]. Stronger associations have been reported for foot pain and pain in other regions of the body [9, 11, 24, 29, 30], suggesting that foot pain may develop as part of a generalised form of osteoarthritis or systemic pain condition.

This study indicates that although it has received relatively little attention in the epidemiological literature, foot pain is highly prevalent, even in young people, and has a significant detrimental impact on health-related quality of life. As the population ages and the prevalence of obesity increases, there is likely to be an increasing prevalence of foot pain. Further research is required to determine best practice models for managing foot pain and to determine whether the provision of foot care services, such as podiatry, are sufficient to meet this increasing demand.