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

This is an interesting result... and will be important not only for aetiological research into PD but also predictive modelling approaches...

J Neurol Neurosurg Psychiatry. 2015 Dec 23. pii: jnnp-2015-312283. doi: 10.1136/jnnp-2015-312283. [Epub ahead of print]

Moisan F, Kab S, Mohamed F, Canonico M, Le Guern M, Quintin C, Carcaillon L, Nicolau J, Duport N, Singh-Manoux A, Boussac-Zarebska M, Elbaz A.

http://jnnp.bmj.com/content/early/2015/12/23/jnnp-2015-312283.long

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.