Fragility, fear of falling, physical activity and falls among older persons: some theoretical considerations to interpret mediation

BACKGROUND: In their letters to the editor, Lacherez et al. Lacherez, P.F., Wood, J.M., Kerr, G.K., 2007. Does activity level mediate or suppress the association between fear of falling and falls? Prev. Med. 31; (Electronic publication ahead of print)] and Hafeman and Schwartz Hafeman, D., Schwartz, S., 2007. Assessing mediation: The necessity of theoretical considerations. Prev. Med. 26; (Electronic publication ahead of print)] questioned the correctness of using the term 'mediation' in our paper Wijlhuizen, G.J., Jong, R. de, Hopman-Rock, M., 2007. Older persons afraid of falling reduce physical activity to prevent outdoor falls. Prev. Med. 44, 260-264.]. In this paper, we concluded that (outdoor) Physical activity mediates the relationship between Fear of falling and outdoor Falls. We investigated whether the term 'inconsistent mediation' might be a more appropriate term to use in this context. METHODS: Based on literature, we describe the relationship between fear of falling, physical activity, and falls within a causal model. RESULTS: Two causal pathways between Fear and Falls exist, with the causal pathway going from Fear of falling via Physical activity to Falls counteracting (is inconsistent with) the causal pathway going from Fear of falling via Hesitancy to Falls. CONCLUSION: The term 'inconsistent mediation' might be more appropriate to describe the causal relationships between Fear of falling, Falls, and Physical activity.