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Background and Objectives: Of all strokes, mild strokes (defined as 5 points or less on the National Institutes of Health Stroke Scale [NIHSS]) are in the majority. However, up to one-third of patients with mild strokes still exhibit significant deficits 3 months after the stroke. Studies on the presumably mildest strokes, defined by zero points on the NIHSS (0-NIHSS) at admission, are scarce. Hence, we aimed to study patient characteristics and outcomes among patients with 0-NIHSS strokes.

Methods: Our retrospective registry-based study included a total of 6,491 adult patients with stroke admitted to 3 different stroke units in Gothenburg, Sweden, from November 2014 to June 2019. Our main outcome was a composite measure including death and activities of daily living (ADL) dependency 3 months after the stroke. Analyses of patient characteristics were followed by adjusted analyses including multiple confounders.

Results: In total, 5,945 patients had data on NIHSS at admission, of whom 1,412 (24%) presented with a 0-NIHSS stroke. Among these, the median age was 72 years, 600 (42%) were female, and 86 (6%) had a hemorrhagic stroke. Among previously ADL-independent patients, 65 (6%) were either dead or ADL-dependent 3 months after the stroke. Prestroke physical inactivity (OR 2.48, 95% CI 1.40–4.38) and age (OR 1.05 per gained year, 95% CI 1.02–1.08) significantly increased the risk of death and ADL dependency.

Discussion: One of 17 patients has either died or become ADL-dependent 3 months after a 0-NIHSS stroke, stressing that these strokes are not always benign. Older and physically inactive patients are at greater risk of an adverse outcome.