Fig. 3

The risk of Parkinson’s disease predicted by the presence of both depressive symptoms and a history of falling at baseline in men (a) and women (b). In men (a), depressive symptoms and a history of falling increased the risk of PD in a sub-additive manner whereas in women (b), the risk of PD was synergistically increased by the presence of both a history of falling and depressive symptoms. Abbreviations: IR, incidence rate; HR, hazard ratio