Table 1.

Demographic Characteristics of Participants and Nonparticipants in the Mayo Clinic Study of Aging, 2004–2013

Characteristic	ACT Group (n = 1,730)			PAS Group (n = 237)			P Valuea	ACT + PAS Group (n = 1,967)			REFUS Groupb (n = 1,301)			P Valuec
	Median (IQRd)	No.	%	Median (IQR)	No.	%		Median (IQR)	No.	%	Median (IQR)	No.	%
Age at enrollment visit or  refusal/exclusion date,  years	80.1 (75.2–83.8)			82.2 (76.7–85.3)			<0.0001	80.4 (75.4–84.0)			81.6 (76.3–85.0)			<0.0001
Female sex		847	49.0		119	50.2	0.72		966	49.1		683	52.5	0.06
Education, years	13 (12.0–16.0)			12 (12.0–15.0)			0.015	13 (12.0–16.0)			12 (11.0–14.0)			<0.0001
≤12 years of education		782	45.2		126	53.2	0.021		908	46.2		827	63.6	<0.0001
Charlson comorbidity index  score	3 (2.0–6.0)			4 (2.0–6.0)			0.019	4 (2.0–6.0)			3 (1.0–6.0)			<0.0001
Years from enrollment or first  contact to dementia or  censoringe	6.2 (4.2–6.6)			2.9 (1.2–3.8)			<0.0001	5.2 (3.6–6.6)			3.9 (2.9–4.5)			<0.0001
Incident dementia		243			19				262			152
Alzheimer's disease		175	77.1		12	63.2	0.02		187	76.0		111	74.0
Vascular dementia		19	8.4		6	31.6			25	10.2		25	16.7
Dementia with Lewy bodies		15	6.6		1	5.3			16	6.5		14	9.3
Frontotemporal dementia		3	1.3		0	0.0			3	1.2		0	0.0
Other		15	6.6		0	0.0			15	6.1		0	0.0

Abbreviations: ACT, active surveillance; IQR, interquartile range; PAS, passive surveillance; REFUS, refusal.

^a P value for comparison of the ACT group with the PAS group.

^b The subset of nonparticipants who refused any participation. Incident dementia in the REFUS group was determined entirely by medical record review.

^c P value for comparison of the ACT + PAS group with the REFUS group.

^d 25th–75th percentiles.

^e Censoring events were death, medical record review, or the end of the observation period (September 15, 2013), depending upon the subject group.