Table 1 Baseline characteristics of participants (classified by fish oil use status) (N = 14,920)

Sociodemographics

Sex

 Male

1,959

38.5

3,981

40.5

0.016

 Female

3,134

61.5

5,846

59.5

Age attending assessment centres (Mean ± SD)

61.4

 ± 6.2

59.2

 ± 7.4

 < 0.001

Townsend deprivation index (Mean ± SD)

-1.7

 ± 2.9

-1.5

 ± 3.0

 < 0.001

Ethnic background

 White

4,978

97.7

9,579

97.5

0.346

 Others

115

2.3

248

2.5

Education

 College or university degree

1,580

31.0

3,259

33.2

0.009

 Below degree

3,513

69.0

6,568

66.8

Life Essential 8 scores

 Total score (Mean ± SD)

65.1

 ± 11.4

63.5

 ± 12.3

 < 0.001

 BMI score (Mean ± SD)

71.5

 ± 26.7

69.3

 ± 28.7

 < 0.001

 Nicotine exposure score (Mean ± SD)

72.1

 ± 30.9

71.1

 ± 32.7

 < 0.001

 Physical activity score (Mean ± SD)

78.3

 ± 35.4

72.6

 ± 38.7

 < 0.001

 Sleep health score (Mean ± SD)

89.7

 ± 18.3

88.7

 ± 19.5

 < 0.001

 Diet score (Mean ± SD)

37.5

 ± 28.5

32.1

 ± 28.3

 < 0.001

 Blood lipids score (Mean ± SD)

46.0

 ± 28.4

48.0

 ± 29.3

 < 0.001

 Blood glucose score (Mean ± SD)

90.3

 ± 19.3

89.3

 ± 20.8

 < 0.001

 Blood pressure score (Mean ± SD)

35.1

 ± 26.9

37.0

 ± 27.0

 < 0.001

Lifestyle

BMI (Mean ± SD)

27.0

 ± 4.3

27.3

 ± 4.8

 < 0.001

Smoking status

 Never

2,592

50.9

5,055

51.5

 < 0.001

 Former

2,156

42.3

3,865

39.3

 Current

345

6.8

907

9.2

Alcohol consumption

 Never

174

3.4

405

4.1

0.026

 Former

202

4.0

445

4.5

 Current

4,717

92.6

8,977

91.4

Vitamin or mineral supplement use

3,365

66.1

3,008

30.6

 < 0.001

Oily fish consumption (≥ 2 servings/week)

3,483

68.4

5,786

58.9

 < 0.001

Clinical

Prior cardiovascular diseases

374

7.3

752

7.7

0.025

Cancer diagnoses (Top 5)

 Breast

1,739

34.1

3,150

32.1

0.013

 Genitourinary

1,114

21.9

1,959

20.0

0.010

 Digestive organs/Gastrointestinal

505

9.9

1,199

12.2

 < 0.001

 Melanoma

466

9.1

836

8.5

0.197

 Hematological

382

7.5

869

8.8

0.010

Class of cancer diagnoses (ICD codes)

 Lip, oral cavity and pharynx (C00-14)

94

1.8

214

2.2

0.395

 Digestive organs (C15-26)

505

9.9

1,199

12.2

 < 0.001

 Respiratory and intrathoracic organs (C30-39)

104

2.0

215

2.2

0.823

 Bone and articular cartilage (C40-41)

22

0.4

41

0.4

1

 Malignant melanoma of skin (C43)

466

9.1

836

8.5

0.395

 Mesothelial and soft tissue (C45-49)

54

1.1

95

1.0

0.823

 Breast (C50)

1,739

34.1

3,150

32.1

0.037

 Female genital organs (C51-58)

471

9.2

906

9.2

1

 Male genital organs (C60-63)

896

17.6

1,519

15.5

0.006

 Urinary tract (C64-68)

219

4.3

442

4.5

0.823

 Eye, brain and other parts of CNS (C69-72)

49

1.0

113

1.1

0.584

 Thyroid and other endocrine glands (C73-75)

74

1.5

183

1.9

0.222

 Ill-defined, secondary and unspecified sites (C76-80)

44

0.9

89

0.9

1

 Primary, of lymphoid, haematopoietic and related tissue (C81-96)

382

7.5

869

8.8

0.026

Age at first cancer diagnosis (Mean ± SD)

53.5

 ± 9.9

51.9

 ± 10.4

 < 0.001

Year since cancer diagnosis (Median [IQR))

6.0

2.0–12.0

5.0

2.0–11.0

 < 0.001