Table 1 Descriptive statistics of total study sample and the categories of muscle strength

Mean age at start of follow-up

19.0

19.0

19.0

19.0

Mean height in centimeters (SD)

178.0 (6.3)

176.4 (6.5)

178.0 (6.2)

179.5 (6.1)

Mean mass in kilograms (SD)

66.5 (9.3)

60.9 (7.8)

66.3 (8.0)

72.4 (9.4)

Mean arm flexion strength in N (SD)

370 (79)

292 (39)

364 (48)

460 (69)

Mean knee extension strength in N (SD)

533 (103)

431 (67)

532 (69)

638 (85)

Mean hand grip strength in N (SD)

608 (98)

508 (63)

605 (64)

711 (77)

Body mass index (%)

 <18.5

5,323 (13.8)

3,169 (32.8)

1,971 (10.2)

183 (1.9)

 18.5 to 24.9

30,697 (79.6)

6,246 (64.7)

16,340 (84.7)

8,111 (84.1)

 ≥25 to 29.9

2,242 (5.8)

204 (2.1)

880 (4.6)

1,158 (12.0)

 ≥30

326 (0.8)

28 (0.3)

103 (0.5)

195 (2.0)

Smoking (%)

 Non-smoker

15,754 (40.8)

4,125 (42.8)

7,664 (39.7)

3,965 (41.1)

 1 to 10 daily cigarettes

12,646 (32.8)

3,128 (32.4)

6,438 (33.4)

3,080 (31.9)

 10+ daily cigarettes

10,188 (26.4)

2,394 (24.8)

5,192 (26.9)

2,602 (27.0)

Alcohol as grams/week (%)*

n = 37,620

n = 9,401

n = 18,799

n = 9,420

 0

2,331 (6.2)

738 (7.9)

1,058 (5.6)

535 (5.7)

 1 to 100

22,923 (60.9)

5,643 (60.0)

11,473 (61.0)

5,807 (61.6)

 101 to 250

9,529 (25.3)

2,354 (25.0)

4,800 (25.5)

2,375 (25.2)

 251+

2,837 (7.5)

666 (7.1)

1,468 (7.8)

703 (7.5)

Cardiorespiratory fitness (%)*

n = 30,941

n = 7,174

n = 15,694

n = 8,073

 Low

15,509 (50.1)

3,403 (47.4)

7,910 (50.4)

4,196 (52.0)

 High

15,432 (49.9)

3,771 (52.6)

7,784 (49.6)

3,877 (48.0)

Attained education 1990 (%)*

n = 35,332

n = 8,815

n = 17,678

n = 8,839

 9 years or less

12,534 (35.5)

2,887 (32.8)

6,057 (34.3)

3,590 (40.6)

 Secondary

14,188 (40.2)

3,432 (38.9)

7,270 (41.1)

3,486 (39.4)

 Higher

8,610 (24.4)

2,496 (28.3)

4,351 (24.6)

1,763 (19.9)

Parental socioeconomic status (%)*

n = 38,581

n = 9,645

n = 19,290

n = 9,646

 Blue collar

19,469 (50.5)

4,674 (48.5)

9,729 (50.4)

5,066 (52.5)

 Lower white collar

10,986 (28.5)

2,696 (28.0)

5,492 (28.5)

2,798 (29.0)

 Upper white collar

6,214 (16.1)

1,822 (18.9)

3,110 (16.1)

1,282 (13.3)

 Other

1,912 (5.0)

453 (4.7)

959 (5.0)

500 (5.2)