Table 1. Descriptive Statistics of All US Medicare Fee-for-Service Beneficiaries Included in the Alzheimer Disease and Related Dementias Cohort From 2000 Through 2016.
| Demographic at study entry | Values |
|---|---|
| Total No. of beneficiaries | 61 662 472 |
| Individual-level covariate, No. (%) | |
| Sex | |
| Female | 34 010 915 (55.2) |
| Male | 27 651 557 (44.8) |
| Age, y | |
| 65-74 | 47 237 464 (76.6) |
| 75-84 | 10 583 080 (17.2) |
| ≥85 | 3 841 928 (6.2) |
| Race and ethnicity | |
| Black | 5 421 282 (8.8) |
| White | 52 044 489 (84.4) |
| Othera | 4 196 701 (6.8) |
| Medicaid eligibility | |
| Not eligible | 53 991 858 (87.6) |
| Eligible | 7 670 614 (12.4) |
| US region | |
| Northeast | 12 354 729 (20.0) |
| South | 23 483 516 (38.1) |
| Midwest | 14 656 222 (23.8) |
| West | 11 168 005 (18.1) |
| Zip code–level covariate, median (IQR)b | |
| Natural environment measures | |
| NDVI | 0.52 (0.36-0.63) |
| Park cover, % | 7.8 (2.2-18.0) |
| Blue space cover (1000-m buffer), % | 0.5 (0.1-3.4) |
| Aggregated data with ≥1.0% blue space cover, % | 41.4 |
| US Census covariates and American Community Survey | |
| Population density (persons/square mile) | 608.2 (84.3-3096.3) |
| Median home value ($1000) | 144.0 (92.2-239.5) |
| Median household income ($1000) | 46.7 (36.6-61.9) |
| With less than a high school degree, % | 24.3 (15.1-36.4) |
| Below the poverty level, % | 8.5 (5.4-13.4) |
| Owner-occupied housing units, % | 71.5 (58.8-80.6) |
| Black race, % | 3.9 (0.8-14.5) |
| Hispanic ethnicity, % | 5.3 (1.8-16) |
| BRFSS covariate | |
| Ever smoked, % | 46.2 (41.5-50.5) |
| Other environmental exposures | |
| Summer temperature, °C | 29.8 (27.3-32.5) |
| Summer specific humidity, g of water vapor/kg of dry air | 12.0 (10.4-14.4) |
| Summer total precipitation (daily total), mm | 3.1 (1.9-4.2) |
| PM2.5, μg/m3 | 9.7 (7.8-11.8) |
| NO2, ppb | 16.6 (10.9-24.8) |
Abbreviations: BRFSS, Behavioral Risk Factor Surveillance System; NDVI, normalized difference vegetation index; NO2, nitrogen dioxide; PM2.5, particulate matter <2.5 µm.
a
Includes American Indian or Alaska Native, Asian, Hispanic, and other or unknown race or ethnicity.
b
Descriptive statistics of the zip code–level covariates are given for the strata (aggregated data for 2000-2016 based on zip code, year, sex, race and ethnicity, Medicaid eligibility, 2-year categories of age at study entry and year of follow-up). Descriptive statistics of the zip code–level covariates for the Parkinson Disease cohort are shown in eTable 1 in Supplement 1.