The obvious consequences of low-quality sleep are: tiredness or sleepiness during the day, brain fog, difficulty focusing or paying attention, forgetfulness, increased errors or accidents, irritability and mood issues, ongoing stress or increased anxiety which may develop into low mood and depression.
There is a large body of scientific research confirming that low-quality sleep may result in serious health problems.
Doctor Chan-Won Kim an associate professor at Kangbuk Samsun Hospital in Seoul analysed data from 106385 participants and found that individuals with either considerable changes in sleep duration or persistently short sleep were at an increased risk of hypertension. LINK
Professor Shahrad Taheri, from Weill Cornell Medical College in Qatar, recruited 522 patients with newly diagnosed type 2 diabetes mellitus. He compared participants who had no weekday sleep debt with those who had weekday sleep debt. People from the latter group were 72% more likely to be obese. Weekday sleep debt was significantly associated with obesity and insulin resistance. At 12 months, for every 30 minutes of weekday sleep debt, the risk of obesity and diabetes was increased by 17% and 39%, respectively. LINK
Another study conducted in China looked at 282 subfertile couples referred to a Chinese fertility clinic. It found that Poor sleep quality has been linked to lower semen quality and a lower fertilisation rate of 60.13%. LINK