Table 1 Descriptive statistics of the study population and variables examined in univariable mixed effect model analysis

Sex

Female

204,335 (47.0)

219,425 (48.3)

Baseline

< 0.001

Male

229,215 (52.7)

232,000 (51.1)

1.06 (1.05–1.07)

< 0.010

Not recorded

1556 (0.4)

2509 (0.6)

0.71 (0.66–0.76)

< 0.001

Neutering

Entire

232,152 (53.4)

252,014 (55.5)

Baseline

< 0.001

Neutered

201,399 (46.3)

199,412 (43.9)

1.10(1.09–1.11)

< 0.001

Not recorded

1555 (0.4)

2508 (0.6)

0.71 (0.66–0.75)

< 0.001

Sex-neuter

Female Entire

106,953 (24.6)

122,389 (27.0)

Baseline

< 0.001

Female Neutered

97,382 (22.4)

97,036 (21.4)

1.15(1.14–1.17)

< 0.001

Male Entire

125,198 (28.8)

129,624 (28.6)

1.11(1.10–1.12)

< 0.001

Male Neutered

104,017 (23.9)

102,376 (22.6)

1.17(1.16–1.19)

< 0.001

Not recorded

1556 (0.4)

2509 (0.6)

0.75 (0.71–0.80)

< 0.001

Insurance

Uninsured

370,530 (85.2)

402,314 (88.6)

1.70(1.67–1.73)

< 0.001

Insured

64,578 (14.8)

51,742 (11.4)

Baseline

< 0.001

KC or not

Not KC recognised

128,963 (29.6)

129,871 (28.6)

Baseline

< 0.001

KC recognised

305,133 (70.1)

321,166 (70.7)

0.95 (0.95–0.96)

< 0.001

Not recorded

1011 (0.2)

2944 (0.6)

0.36 (0.34–0.39)

< 0.001

Purebred or not

Crossbred

91,490 (21.0)

98,752 (21.8)

Baseline

< 0.001

Designer crossbred

29,588 (6.8)

21,589 (4.8)

1.52(1.49–1.54)

< 0.001

Purebred

313,018 (71.9)

330,696 (72.8)

1.02(1.02–1.03)

< 0.001

Not recorded

1011 (0.2)

2944 (0.6)

0.36 (0.34–0.39)

< 0.001

Common breeds

Crossbred

91,490 (21.0)

98,752 (21.7)

Baseline

< 0.001

Labrador Retriever

30,706 (7.1)

28,062 (6.2)

1.17(1.15–1.19)

< 0.001

Jack Russell Terrier

21,945 (5.0)

25,592 (5.6)

0.92(0.90–0.94)

< 0.001

Staffordshire bull terrier

20,923 (4.8)

30,960 (6.8)

0.72(0.71–0.73)

< 0.001

Cocker Spaniel

17,263 (4.0)

14,291 (3.1)

1.28(1.25–1.31)

< 0.001

Shih-Tzu

16,811 (3.9)

15,529 (3.4)

1.16(1.13–1.19)

< 0.001

Yorkshire Terrier

13,032 (3.0)

14,610 (3.2)

0.97(0.95–1.00)

< 0.001

Chihuahua

12,640 (2.9)

12,032 (2.6)

1.13(1.10–1.16)

< 0.001

Border Collie

11,471 (2.6)

10,460 (2.3)

1.17(1.14–1.20)

< 0.001

Cockapoo

10,905 (2.5)

7026 (1.5)

1.72(1.67–1.78)

< 0.001

German Shepherd Dog

10,119 (2.3)

10,860 (2.4)

1.00(0.97–1.05)

0.980

West Highland White Terrier

9100 (2.1)

9458 (2.1)

1.02(0.99–1.05)

0.190

Cavalier King Charles Spaniel

8327 (1.9)

8630 (1.9)

1.04(1.01–1.07)

0.012

Pug

7996 (1.8)

7992 (1.8)

1.11(1.08–1.15)

< 0.001

French Bulldog

7165 (1.6)

8975 (2.0)

0.92(0.89–0.94)

< 0.001

Bichon Frise

6633 (1.5)

6454 (1.4)

1.13(1.10–1.18)

< 0.001

Lhasa Apso

6664 (1.5)

5690 (1.3)

1.17(1.13–1.21)

< 0.001

Springer Spaniel

5467 (1.3)

5278 (1.2)

1.05(1,01–1.09)

0.016

Border Terrier

5330 (1.2)

4165 (0.9)

1.25(1.30–1.41)

< 0.001

Golden Retriever

5060 (1.2)

4580 (1.0)

1.23(1.19–1.30)

< 0.001

Purebred-other

115,049 (26.4)

121,641 (26.8)

1.04(1.03–1.05)

< 0.001

Breed not recorded

1012 (0.2)

3019 (0.7)

0.38 (0.36–0.41)

< 0.001

Kennel Club group

Not KC Recognised

128,963 (29.6)

129,871 (28.6)

Baseline

< 0.001

Gundog

69,812 (16.0)

63,270 (13.9)

1.10(1.08–1.11)

< 0.001

Hound

14,913 (3.4)

15,985 (3.5)

0.96(0.93–0.98)

< 0.001

Pastoral

25,188 (5.8)

25,510 (5.6)

0.99(0.97–1.01)

0.190

Terrier

64,794 (14.9)

78,244 (17.2)

0.82(0.81–0.83)

< 0.001

Toy

63,465 (14.6)

66,254 (14.6)

0.98(0.97–0.99)

0.004

Utility

49,693 (11.4)

51,229 (11.3)

0.97(0.96–0.99)

< 0.001

Working

17,268 (4.0)

20,674 (4.6)

0.83(0.82–0.86)

< 0.001

Not recorded

1011 (0.2)

2944 (0.6)

0.36 (0.34–0.39)

< 0.001

NUTS region

North East England

16,559 (3.8)

13,351 (2.9)

Baseline

0.340

North West England

36,383 (8.4)

40,720 (9.0)

0.89(0.77–1.03)

0.330

Yorkshire and Humber

35,433 (8.1)

28,499 (6.3)

1.10(0.93–1.30)

0.450

East Midlands

34,970 (8.0)

31,860 (7.0)

1.06(0.90–1.24)

0.650

West Midlands

100,497 (23.1)

93,157 (20.5)

0.96(0.82–1.14)

0.770

East of England

50,888 (11.7)

56,472 (12.4)

1.04(0.91–1.19)

0.720

London

42,126 (9.7)

49,909 (11.0)

1.15(0.92–1.43)

0.220

South East England

55,301 (12.7)

66,518 (14.6)

0.92(0.81–1.06)

0.480

South West England

25,609 (5.9)

32,023 (7.1)

0.84(0.73–0.97)

0.150

Wales

16,273 (3.7)

19,885 (4.4)

0.84(0.67–1.07)

0.260

Scotland

18,835 (4.3)

18,009 (4.0)

1.08(0.87–1.34)

0.580

Northern Ireland

2234 (0.5)

3653 (0.8)

0.79(0.59–1.06)

0.190

Not recorded

0

0

Clinic IMD ranked

1

88,189 (20.3)

90,225 (20.0)

Baseline

0.150

2

150,154 (34.5)

149,790 (33.2)

1.01 (0.89–1.15)

0.830

3

71,017 (16.3)

82,013 (18.2)

1.00 (0.88–1.15)

0.940

4

63,948 (14.7)

70,477 (15.6)

1.02 (0.89–1.17)

0.780

5

56,286 (12.9)

55,628 (12.3)

1.15 (1.01–1.32)

0.040

Not recorded

5514 (1.3)

3120 (0.7)

4.27 (2.11–8.65)

< 0.001

Owner IMD ranked

1

93,551 (21.5)

91,857 (20.3)

Baseline

< 0.001

2

78,351 (18.0)

81,759 (18.1)

1.04 (1.02–1.06)

< 0.001

3

85,233 (19.6)

85,296 (18.8)

1.07 (1.05–1.09)

< 0.001

4

83,725 (19.3)

81,688 (18.0)

1.08 (1.06–1.09)

< 0.001

5

55,973 (12.9)

55,475 (12.3)

1.05 (1.03–1.07)

< 0.001

Not recorded

37,949 (8.7)

56,543 (12.5)

0.60 (0.58–0.61)

< 0.001

Vet Group

A

218,957 (50.3)

252,138 (55.9)

Baseline

< 0.001

B

23,668 (5.4)

19,028 (4.2)

1.99 (1.71–2.30)

< 0.001

C

64,942 (14.9)

86,392 (19.1)

1.03 (0.94–1.14)

0.540

D

124,487 (28.6)

92,946 (20.6)

1.23 (1.11–1.37)

< 0.001

E

3054 (0.7)

749 (0.2)

2.04(1.15–3.61)

0.020

Bodyweight (kg) – 10 kg bins

0- < 10

131,722 (30.3)

133,008 (29.3)

Baseline

< 0.001

10- < 20

182,679 (42.0)

187,204 (41.2)

0.99(0.98–1.00)

0.110

20- < 30

65,728 (15.1)

72,403 (16.0)

0.92(0.90–0.93)

< 0.001

30- < 40

44,429 (10.2).

45,274 (10.0)

0.99(0.97–1.00)

0.100

> 40

7966 (1.8)

10,766 (2.4)

0.74(0.72–0.77)

< 0.001

Not recorded

2581 (0.6)

5201 (1.1)

0.71 (0.67–0.75)

< 0.001

Age

<1y

95,736 (22.0)

35,070 (7.7)

Baseline

< 0.001

1-5y

177,115 (40.7)

182,980 (40.4)

0.31(0.30–0.31)

< 0.001

5-8y

83,467 (19.2)

88,698 (19.6)

0.28(0.28–0.29)

< 0.001

>8y

76,573 (17.6)

138,056 (30.4)

0.17(0.16–0.17)

< 0.001

Missing

2192 (0.5)

8666 (1.9)

0.08 (0.08–0.09)

< 0.001