Night-shift intensity, duration, cardiovascular susceptibility and incident cardiovascular disease: UK Biobank study

Night-shift work has been associated with adverse cardiovascular outcomes. It remains unclear whether the cardiovascular association of night-shift exposure differs according to underlying baseline cardiovascular susceptibility and whether short-term intensity and longer-term duration show similar patterns.

We analyzed 85,322 UK Biobank participants with occupational night-shift information. Baseline cardiovascular disease risk profile was classified as low, intermediate, or high using a composite score based on cardiovascular disease polygenic risk score tertiles, current smoking, obesity, low moderate-to-vigorous physical activity, and insomnia. Night-shift exposure was evaluated in two ways: monthly intensity and yearly duration, each categorized as none, low, or high. Incident cardiovascular disease was identified from inpatient records. Cox proportional hazards models were evaluated for the associations.

Of 85,322 participants, 24,696 were classified as low cardiovascular disease risk, 49,332 as intermediate risk, and 11,294 as high risk. Across all strata, workers without night-shift exposure generally had the lowest incidence of cardiovascular disease. In the low-risk group, high monthly intensity and high yearly duration were each associated with similar increased risk and having more pronounced in high-risk group. For monthly intensity, the aHR were 1.35 (95% CI 1.19-1.52) and 1.22 (95% CI 1.08-1.37) for low- and high-intensity groups, respectively, whereas for yearly duration the corresponding aHR were 1.21 (95% CI 1.06-1.37) and 1.34 (95% CI 1.19-1.51).

Among workers with occupational night-shift information, the association between night-shift exposure and incident cardiovascular disease was strongest in those with greater baseline cardiovascular susceptibility. Compared with monthly intensity, yearly duration showed a more consistent exposure-response pattern.