Table 1 Characteristics of the study population at age 50.

From: Association of sleep duration in middle and old age with incidence of dementia

  Sleep duration at age 50 Dementia status at end of follow-up
Short: ≤6 h Normal: 7 h Long: ≥8 h P No dementia Dementia P
N 3149 3624 1186   7438 521  
Women 1035 (32.9) 1118 (30.9) 456 (38.5) <0.001 2390 (32.1) 219 (42.0) <0.001
Ethnicity, Nmon-white 326 (10.4) 309 (8.5) 163 (13.7) <0.001 719 (9.7) 79 (15.2) <0.001
Less than secondary school diploma 1522 (48.3) 1722 (47.5) 575 (48.5) 0.75 3509 (47.2) 310 (59.5) <0.001
Married/cohabiting 2296 (72.9) 2823 (77.9) 897 (75.6) <0.001 5647 (75.9) 369 (70.8) 0.009
Moderate alcohol drinking (1–14 units per week) 1695 (53.8) 2042 (56.4) 618 (52.1) 0.02 4082 (54.9) 273 (52.4) 0.27
Current smokers 519 (16.5) 552 (15.2) 168 (14.2) 0.13 1138 (15.3) 101 (19.4) 0.013
Moderate-to-vigorous physical activity (h), M (SD) 3.3 (3.9) 3.4 (3.5) 3.2 (3.6) 0.14 3.3 (3.7) 3.3 (3.7) 0.78
Daily fruit and vegetable consumption 1953 (62.0) 2341 (64.6) 777 (65.5) 0.03 4774 (64.2) 297 (57.0) 0.001
BMI ≥ 30 kg/m² 414 (13.2) 355 (9.8) 120 (10.1) <0.001 823 (11.1) 66 (12.7) 0.26
Diabetes 97 (3.1) 80 (2.2) 22 (1.9) 0.02 182 (2.5) 17 (3.3) 0.25
Hypertension 779 (24.7) 783 (21.6) 288 (24.3) 0.006 1700 (22.9) 150 (28.8) 0.002
Cardiovascular disease 105 (3.3) 91 (2.5) 28 (2.4) 0.07 214 (2.9) 10 (1.9) 0.20
GHQ depression 577 (18.3) 439 (12.1) 143 (12.1) <0.001 1070 (14.4) 89 (17.1) 0.09
CNS medications 169 (5.4) 130 (3.6) 59 (5.0) 0.001 322 (4.3) 36 (6.9) 0.006
Mental disorders before age 65 259 (8.2) 231 (6.4) 93 (7.8) 0.01 541 (7.3) 42 (8.1) 0.51
  1. Values are No. (%) unless stated otherwise. Two-sided Ps for heterogeneity were estimated using χ² test for categorical variables, and ANOVA for continuous variables by sleep duration groups and Student’s t test by dementia groups for continuous variables.
  2. BMI body mass index, CNS central nervous system, GHQ general health questionnaire, M mean, SD standard deviation.