In cross-sectional studies using mediation analyses, it has been proposed that leptin (an adipokine mainly secreted by adipose tissue, with proinflammatory effects) partially mediates the association between obesity and pain in hand osteoarthritis [35], that pain is a significant mediator (of 22–44%) of the association between obesity and disability in women aged 70 years and older [36], and that long-term conditions play a mediating role in the relationship between obesity and reduced quality of life [37]. This evidence concerns the gene LEP and osteoarthritis, hand.