This retrospective cohort study included 712 patients with acute ischaemic stroke in China who received reperfusion therapy (intravenous thrombolysis or combined endovascular therapy) between October 2018 and March 2022. The analysis aimed to investigate whether the time of day at symptom onset was associated with functional outcomes after reperfusion treatment. The study design and sampling period were reported in the source; details beyond the enrolment window and treatment types were not provided in the source text.
Patients were categorised into two primary groups by onset clock time: day-onset (06:00–18:00) and night-onset (18:00–06:00). In addition, analyses were performed using six 4-hour onset intervals to examine finer temporal patterns. The 4-hour interval approach allowed identification of specific night periods with differing associations with outcome.
The primary outcome was functional status at 3 months, measured by the modified Rankin Scale (mRS). Outcomes were dichotomised with mRS scores 0–2 classified as favourable and scores 3–6 as unfavourable. Three-month mRS was the sole reported primary endpoint in the source.
The investigators used multiple methods to account for confounding and to test the robustness of associations between time of onset and outcome. These included propensity score matching (PSM), inverse probability of treatment weighting (IPTW), and overlap weighting (OW). Multivariable logistic regression was also used to provide adjusted odds ratios. Exact covariates included in the adjustments were not listed in the source text.
Of the 712 patients, 286 had night-onset stroke and 426 had day-onset stroke. At 3 months, unfavourable outcomes occurred in 148/286 (51.7%) of the night-onset group versus 182/426 (42.7%) of the day-onset group. In unadjusted analysis, night-onset stroke was associated with increased odds of an unfavourable outcome (OR 1.44, 95% CI 1.06 to 1.94; p=0.018).
This association remained statistically significant after multiple approaches to adjustment and weighting. Using propensity score matching gave OR 1.45 (95% CI 1.01 to 2.08; p=0.044). Inverse probability of treatment weighting produced OR 1.42 (95% CI 1.02 to 1.96; p=0.036). Overlap weighting yielded OR 1.42 (95% CI 1.03 to 1.96; p=0.032). Multivariable-adjusted analysis also confirmed the association (adjusted OR 1.55, 95% CI 1.07 to 2.22; p=0.019).
These consistent findings across analytic methods indicate that night-time symptom onset was associated with a higher likelihood of poor functional outcome at 3 months among patients treated with reperfusion.
When onset time was examined in 4-hour intervals, a specific night-time window showed a markedly stronger association. Onset during 22:00–02:00 was significantly associated with unfavourable 3-month outcome in adjusted analysis (adjusted OR 2.44, 95% CI 1.34 to 4.43; p=0.003). The source did not report adjusted effect estimates for all other individual intervals in detail.
In this cohort of patients receiving reperfusion therapy for acute ischaemic stroke, night-onset stroke was associated with poorer functional outcomes at 3 months compared with day-onset stroke. The association persisted after multiple statistical adjustments and weighting strategies, and the 22:00–02:00 interval demonstrated a particularly elevated adjusted odds of unfavourable outcome.
The authors conclude that time of symptom onset, especially during late-night hours, may be an independent factor associated with worse post-reperfusion functional outcome and suggest that these temporal patterns merit further investigation.
As a retrospective cohort from a single-country dataset reported in the source, the study carries limitations inherent to observational designs. The source did not provide a full list of covariates used for adjustment, nor did it report centre-level, process-of-care, or imaging-related variables in the provided summary. The authors recommended multicentre prospective studies to validate and further explore the observed association between time of day at stroke onset and outcomes after reperfusion therapy.
Trial registration: Chinese Clinical Trial Registry Identifier ChiCTR2500101844.