Table 4.

Association between shift work and cardiovascular disease (CVD) by subgroup

	Incident CVD			Fatal CVD
	HR (95% CI)	P	P interaction	HR (95% CI)	P	P interaction
Age			0.32			0.02
≤50 years	1.08 (0.98, 1.18)	0.30		0.76 (0.54, 1.08)	0.84
>50 years	1.11 (1.06, 1.17)	0.002		1.41 (1.20, 1.65)	0.002
Sex			0.0007			0.82
Female	1.16 (1.07, 1.27)	0.005		1.26 (0.92, 1.71)	0.84
Male	1.08 (1.02, 1.14)	0.045		1.24 (1.05, 1.46)	0.13
Education attainment			0.11			0.34
Non-university	1.09 (1.04, 1.14)	0.0084		1.31 (1.12, 1.54)	0.01
University	1.20 (1.08, 1.32)	0.045		1.01 (0.71, 1.44)	0.96
Area-based deprivation			0.16			0.98
More deprived	1.13 (1.07, 1.20)	0.002		1.24 (1.03, 1.48)	0.22
Less deprived	1.07 (1.00, 1.15)	0.26		1.27 (1.00, 1.62)	0.39
Hours of work per week			0.47			0.23
≤37	1.12 (1.05, 1.19)	0.01		1.14 (0.92, 1.42)	0.96
>37	1.10 (1.03, 1.17)	0.02		1.32 (1.08, 1.60)	0.07
Heavy manual labour			0.004			0.72
Never or rarely	1.18 (1.10, 1.27)	0.002		1.16 (0.90, 1.49)	0.96
Sometimes or more	1.05 (0.99, 1.11)	0.28		1.29 (1.08, 1.54)	0.13
Chronotype			0.40			0.56
Definitely morning	1.09 (1.00, 1.19)	0.24		1.38 (1.04, 1.82)	0.22
More morning	1.07 (0.98, 1.17)	0.30		1.12 (0.83, 1.51)	0.96
More evening	1.10 (1.01, 1.20)	0.21		1.36 (1.04, 1.77)	0.22
Definitely evening	1.13 (0.97, 1.31)	0.30		1.43 (0.90, 2.28)	0.84

Adjusted for age, sex, ethnicity, education, deprivation, hours of work per week, duration of current job, walking/standing at work and heavy manual/physical work.

P-values for subgroup analyses were corrected using Holm’s Bonferroni procedure.