Parkinson disease male-to-female ratios increase with age: French nationwide study and meta-analysis

Abstract

Background: Parkinson's disease (PD) is 1.5 times more frequent in men than women. Whether age modifies this ratio is unclear. We examined whether male-to-female (M-F) ratios change with age through a French nationwide prevalence/incidence study (2010) and a meta-analysis of incidence studies.

Methods: We used French national drug claims databases to identify PD cases using a validated algorithm. We computed M-F prevalence/incidence ratios overall and by age using Poisson regression. Ratios were regressed on age to estimate their annual change. We identified all PD incidence studies with age/sex-specific data, and performed a meta-analysis of M-F ratios.

Results: On the basis of 149 672 prevalent (50% women) and 25 438 incident (49% women) cases, age-standardised rates were higher in men (prevalence=2.865/1000; incidence=0.490/1000 person-years) than women (prevalence=1.934/1000; incidence=0.328/1000 person-years). The overall M-F ratio was 1.48 for prevalence and 1.49 for incidence. Prevalence and incidence M-F ratios increased by 0.05 and 0.14, respectively, per 10 years of age. Incidence was similar in men and women under 50 years (M-F ratio <1.2, p>0.20), and over 1.6 (p<0.001) times higher in men than women above 80 years (p trend <0.001). A meta-analysis of 22 incidence studies (14 126 cases, 46% women) confirmed that M- F ratios increased with age (0.26 per 10 years, p trend=0.005).

Conclusions: Age-increasing M-F ratios suggest that PD aetiology changes with age. Sex-related risk/protective factors may play a different role across the continuum of age at onset. This finding may inform aetiological PD research.

Keywords: EPIDEMIOLOGY; PARKINSON'S DISEASE; STATISTICS.

Figure 1

Age-specific male-to-female incidence and prevalence ratios of Parkinson's disease (France, 2010). Solid line, observed age-specific male-to-female ratios estimated by modelling prevalence and incidence through Poisson regression. Grey area, 95% CIs of observed male-to-female ratios. Dashed line, linear regression of male-to-female ratios weighted by the inverse of their variance on age (in years, centred at 40 years).

Figure 2

Systematic review of age-specific male-to-female incidence ratios of Parkinson's disease. Circles represent observed male-to-female incidence ratios for each study by age-by-sex strata, estimated by modelling incidence through Poisson regression; their size is proportional to the variance of the male-to-female incidence ratios, and more precise estimates are represented by larger circles. Solid line, linear regression of male-to-female incidence ratios weighted by the inverse of their variance on age (in years, centred at 40 years). Dashed line, 95% CIs of the linear regression.