Is Sleep Quality good for cognitive function?

The evidence points that way, though it's not yet conclusive. The evidence base for this topic is comparatively weak and diffuse: available studies address related but distinct subjects, such as loneliness and sleep, herbal supplements (ashwagandha, lemon balm) and psychological well-being, and gut-brain-axis nutrition, none of which directly test structured interventions to improve sleep quality itself. That's reflected in an evidence score of 50/100 for its role in cognitive function, drawn from 4 studies (1 RCT), with an estimated impact on longevity rated moderate (35/100).