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★★☆Single study — solid evidence, such as one good trial or a large observational dataset, but not replicated at the top tier.
A flat cortisol day before bypass went with more heart events after
Among 250 patients measured a month before heart bypass, those whose cortisol fell least across the day had more major cardiac events or deaths over the next 2.7 years.
What the study found
A flat cortisol curve a month before bypass predicted worse outcomes
Among 250 patients whose cortisol was measured a month before heart bypass surgery, those whose level fell least across the day had more major cardiac events or deaths over the next 2.7 years. Both the waking reading and the evening one moved the result.
The caveat · Surgery ahead may distort cortisol
One hospital, 250 people. Facing major surgery can itself distort cortisol patterns, so this may not reflect ordinary life. A flatter drop may also mark someone who is already sicker, rather than adding risk of its own.