Table 3.

ASMase activity quartiles^a and the age at onset of PD.

	Quartile 1	Quartile 2	Quartile 3	Quartile 4	p valueb
ASMase activity range (μmol/l/h)	<3.485	3.485–4.46	4.46–5.64	>5.64
All patients
Nc	134	148	146	120
Average AAO ± SD	58.6 ± 10.3	58.2 ± 12.2	58.2 ± 12.4	62.2 ± 11.0	p=0.01
All patients with late-onset PD (AAO ≥ 50)
N	115	117	111	104
Average AAO ± SD	61.5 ± 7.2	63.0 ± 7.5	63.5 ± 8.3	65.0 ± 8.8	p=0.01
All patients excluding GBA and LRRK2 mutation carriers
N	109	119	113	89
Average AAO ± SD	57.4 ± 10.4	58.2 ± 12.5	58.1 ± 12.9	63.2 ± 11.2	p=0.003
All patients with late-onset PD, excluding GBA and LRRK2 mutation carriers
N	91	93	85	80
Average AAO ± SD	60.7 ± 7.1	63.4 ± 7.6	64.0 ± 8.2	65.5 ± 9.1	p=0.001

ASMase, acid sphingomyelinase; N, number; AAO, age at onset; SD, standard deviation.

^aQuartiles were determined according to ASMase activity in controls, however nearly identical results were calculated when the quartiles were determined according to patients only, or patients and controls combined.

^bAnalysis of variance (ANOVA).

^cData on AAO was not available for one patient.