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Table 1 Descriptive statistics of the full sample and the within-pair sample I. Data presented for the dizygotic (DZ) and monozygotic (MZ) twins includes those individuals who were available for the within-pair analysis. Values are mean (standard deviation, SD) unless otherwise indicated

From: Frailty and the risk of dementia: is the association explained by shared environmental and genetic factors?

  Full sample Within-pair sample I
N = 41,550 DZ twin individuals
N = 22,062
MZ twin individuals
N = 8110
Age at baseline 58.0 (10.1) 56.7 (9.1) 56.6 (9.1)
Age range at baseline 41–97 41–91 41–88
Women, N (%) 22,193 (53.4) 11,621 (52.7) 4606 (56.8)
BMI 25.0 (3.5) 25.0 (3.5) 24.9 (3.5)
Tobacco user, N (%) 24,491 (58.9) 13,282 (60.2) 4549 (56.1)
Years of education 10.6 (3.2) 10.7 (3.2) 11.0 (3.2)
§Physical activity, median (IQR)
 Born before 1926 1 (1) 1 (1) 1 (1)
 Born after 1926 3 (2) 3 (2) 3 (2)
Living alone, N (%) 9005 (21.7) 4395 (19.9) 1558 (19.2)
FI, median (IQR) 0.108 (0.108) 0.102 (0.108) 0.102 (0.108)
Categorized FI
 Non-frail, N (%) 15,464 (37.2) 8557 (38.8) 3133 (38.6)
 Pre-frail, N (%) 22,354 (53.8) 11,757 (53.3) 4298 (53.0)
 Frail, N (%) 3732 (9.0) 1748 (7.9) 679 (8.4)
Dementia diagnosis during follow-up, N (%) 3183 (7.7) 1364 (6.2) 494 (6.1)
Time to diagnosis, median (IQR) 16.0 (2.4) 16.1 (2.3) 16.1 (2.2)
Died during follow-up, N (%) 9932 (23.9) 2012 (9.1) 756 (9.3)
  1. Note. Participants who used tobacco products include current smokers, ex-smokers, and snuff users at baseline
  2. §Physical activity was assessed using a different questionnaire for those born before 1926 vs after 1926
  3. Abbreviations: BMI body mass index, DZ dizygotic, FI frailty index, IQR interquartile range, MZ monozygotic, N number