The literature concerning gender effect on the incidence and expression of Parkinson’s disease (PD) is far from clear.¹ In this issue of J Neurol Neurosurg Psychiatry, Taylor and colleagues² present a meta-analysis of age adjusted male to female incidence ratios for PD (see page 905). Seventeen relevant studies and over 2500 people with PD were identified. The authors determined an overall male:female (M:F) ratio of 1.46 (95% confidence intervals 1.24, 1.72) but also found a high level of heterogeneity. M:F difference in the incidence of PD increased with age of onset and, notably, while a M:F …