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Subject characteristics
| Characteristic | MZ | DZ |
|---|---|---|
| N of individuals (N of twin pairs) | 502 (251) | 70 (35)a |
| Age, years: mean ± SD (range) | 40±15 (21–77) | 39±16 (21–82) |
| Caucasian/otherwise | 426/76 | 58/12 |
| Female/male | 406/96 | 53/17 |
MZ, monozygotic (genetically identical) twins; DZ, dizygotic (not genetically identical) twins; otherwise, not Caucasian, most of whom were African–American (MZ = 33; DZ = 8).
aThirty-one DZ pairs were same sex, and four were of the opposite sex.
