Table 1: Population Characteristics of Reconstructed Sample.

Headings in bold, subheadings below not bolded.

Sample A: patients with an ICD-10 diagnosis code suggestive of dementia (Supplementary Table S2)

Sample B: patients with a clinic visit during the observation period with a neurologist, psychiatrist, geriatrician, neuropsychologist, or geriatric psychiatrist, but without an ICD-10 diagnosis suggestive of dementia

Sample C: all other patients

Characteristics	Sample A		Sample B		Sample C		Total
Patients (n)	2,900		10,657		27,133		40,690
Demographics a
Age in years, mean (SD)	80.9	0.41	75.8	0.36	74.4	0.36	75.2	0.26
Female, n (%)	1,849	64%	6,328	59%	15,799	58%	23,976	59%
White, n (%)	2,657	92%	10,051	94%	24,986	92%	37,695	93%
Deceased by end study period, n (%)	217	7%	363	3%	429	2%	1,010	2%
Any Cognitive Concern
No, n (%)	226	8%	6,449	62%	22,926	89%	29,600	76%
Yes, n (%)	2,483	92%	3,875	38%	2,748	11%	9,106	24%
Cognitive Status b
Cognitively normal, n (%)	287	11%	7,115	69%	22,840	89%	30,241	78%
Normal vs. MCI, n (%)	96	4%	817	8%	687	3%	1,600	4%
MCI, n (%)	226	8%	969	9%	429	2%	1,624	4%
MCI vs. dementia, n (%)	217	8%	484	5%	258	1%	959	2%
Dementia, n (%)	1,789	66%	636	6%	429	2%	2,854	7%
Unknown, n (%)	96	4%	303	3%	1,030	4%	1,429	4%
Missing Chart Data, n (%)	191	7%	333	3%	1,460	5%	1,984	5%
Cognitive Status by Claims-Based Definitions
Met Base Claims-Based Dementia Definition, n (%)	2,891	100%	908	9%	601	2%	4,400	11%
Met Refined Claims-Based Dementia Definition, n (%)	2,579	89%	575	5%	258	1%	3,412	8%

^aData derived from Partner’s Medicare claims

^bdata abstracted from EHRs

Abbreviations

MCI, mild cognitive impairment; EHR, electronic health record