Table 1

Characteristics of the study sample according to gender and educational attainment

Men

(n = 1,053)

Women

(n = 1,574)

Postmenopausal Women

(n = 1,330)




Educational attainment

Low

High

P value

Low

High

P value

Low

High

P value

(n = 402)

(n = 651)

(n = 587)

(n = 987)

(n = 518)

(n = 812)


Demographic characteristics

% Age group in years

<0.001

<0.001

<0.001

45-54

19.7

42.9

17.6

44.5

12.2

35.3

55-64

23.9

32.1

24.2

33.2

25.9

38.4

65-74

37.8

20.7

35.8

15.8

37.8

18.6

75+

18.7

4.3

22.5

6.5

24.1

7.6

% African American

36.1

19.7

<0.001

43.6

30.6

<0.001

42.9

28.7

<0.001


Lifestyle/clinical characteristics

% Current Smokers

32.1

24.9

0.011

13.3

17.9

0.016

13.3

18.4

0.016

% Current alcohol use

20.4

34.1

<0.001

6.6

17.9

<0.001

6.2

17.2

<0.001

Mean BMI kg/m2 (SD)

27.6(5.0)

28.5(4.8)

0.004

30.2(6.7)

29.1(6.4)

0.001

30.0(6.5)

29.0(6.3)

0.005

% Knee injury

15.9

18.4

0.297

15.7

15.6

0.970

16.4

16.3

0.941


Occupation characteristics

% Physically demanding occupationa

83.3

43.0

<0.001

82.8

38.0

<0.001

82.2

37.4

<0.001

Mean occupational physical activities score (SD)b

10.7(2.6)

10.0(2.7)

<0.001

8.7(3.1)

8.8(3.0)

0.505

8.6(3.0)

8.7(3.1)

0.630


HRT use characteristics

% Current

HRT use

N/A

N/A

N/A

N/A

N/A

N/A

13.9

30.8

<0.001


Radiographic OA

% Radiographic knee OA

32.8

22.9

<0.001

41.9

23.9

<0.001

41.9

24.9

<0.001

% Bilateral radiographic knee OA

19.9

12.1

0.001

28.7

12.7

<0.001

29.2

13.7

<0.001


Symptomatic OA

% Symptomatic knee OA

20.2

11.1

<0.001

27.0

12.1

<0.001

27.1

13.5

<0.001

% Symptomatic bilateral knee OA

5.9

4.0

0.189

13.4

4.7

<0.001

13.1

5.0

<0.001


P values are listed for comparisons between <12 years and 12+ years education within each gender category (men, women, postmenopausal women).

Low educational attainment, <12 years; high educational attainment, ≥ 12 years.

BMI, body mass index; HRT, hormone replacement therapy.

aLaborers, fabricators, service, production, forestry, farming (as opposed to managerial, professional, technical, sales, administrative).

bScale (0-16) increasing for frequency of lifting, standing, walking, and squatting.

Callahan et al. Arthritis Research & Therapy 2010 12:R46   doi:10.1186/ar2956

Open Data