Background/Purpose: Obesity and foot problems are common in older adults and associated with many negative health outcomes. There is limited evidence examining the relation between foot problems and obesity from a population perspective. Previous studies have found higher BMI to be linked with reduced odds of hallux valgus, a common foot disorder, but no study has determined the reason for this unexpected relation. The purpose of this study was to describe the associations between obesity categories, with foot pain and foot disorders (hallux valgus, claw, hammer, overlapping toes), and to determine if these associations differ by foot structure or by foot function in a community-based, cross-sectional study of older men and women.

Methods: We included 2445 participants (contributing 4888 feet) from the Framingham Foot Study between 2002 and 2008. A podiatric-trained examiner performed a validated examination of participantsÕ feet to determine the presence of foot disorders on each foot by comparing the foot to a laminated depiction of the disorder. Foot pain was defined by the question ÒOn most days, do you have pain, aching or stiffness in either foot?Ó Body mass index (BMI, kg/m²) was determined at the time of the foot exam and categorized as normal (<25, referent), overweight (25-30), moderately obese (30-35) and severely obese (35+). Foot structure (cavus, planus) and foot function (pronated, supinated) were defined using the Tekscan Matscan pressure system as the modified arch index and the center of pressure excursion index, respectively. We used sex-specific logistic regression, adjusting for within person correlation, to examine the relation between foot pain and each foot disorder with obesity categories, adjusting for age and further stratified by foot structure and foot function categories in a foot-specific analysis.

Results: Average age was 68 (SD 11) years, 56% were female, BMI was 28 (SD 5) kg/m². 18% of feet had pain, 25% hallux valgus, 2% claw toes, 18% hammer toes, 7% overlapping toes. Severely obese men were more likely to have foot pain (OR=2.4; 95% CI: 1.4-4.3) and claw toes (OR=3.4; 95% CI: 1.1-10.7) compared to normal weight men. In women, there was an increased odds of foot pain with all categories of obesity (Table). Severely obese women were 40% less likely to have hallux valgus (OR=0.61; 95% CI: 0.4-0.9) compared to normal weight women. We saw the same effect in men although it did not reach statistical significance. Patterns of association were the same stratified by foot structure or function in men or in women.

Conclusion: Women are more prone to foot pain and obese women, even more so. Reducing weight may reduce pain and potentially reduce foot problems. Foot structure and foot function do not change the associations between foot problems and obesity. Further studies are needed to determine the mechanism behind these associations and the role of longitudinal trajectories of BMI on foot problems.