Not the OP, but poor sleep duration/quality has a somewhat strong correlation with dehydration, which is a common cause of a white tongue (inflamed papillae).

Not the OP, but poor sleep duration/quality has a somewhat strong correlation with dehydration, which is a common cause of a white tongue (inflamed papillae). Poor sleep duration/quality is also correlated with hypertension/high blood pressure, which is a risk factor for stroke and heart disease. Not to say that lack of sleep causes a white tongue or stroke, but it is plausible that it could be a sign of chronic sleep insufficiency or dehydration.