Non-restorative sleep (waking up tired despite a full night) is linked to a lack of deep sleep and constitutes a major independent risk factor for cardiac and cerebrovascular diseases.

noli's read

Matthew Walker highlights a problem of quality rather than quantity here, a subject extensively documented in scientific literature. It is established by observational studies and meta-analyses that sleep fragmentation or a reduction in slow-wave sleep (deep sleep) is correlated with an increase in cardiovascular risk markers. The concept of an 'independent risk factor' is supported by epidemiological data showing that, even when controlling for other variables, sleep quality influences vascular health. However, it is important to note that non-restorative sleep is a complex symptom that can result from multiple causes (sleep apnea, stress, lifestyle, or metabolic disorders). While the link is strong, labeling it a 'major' risk can sometimes obscure the importance of other equally determinant lifestyle factors. Science confirms that sleep structure is as crucial as its duration, although the precise measurement of 'deep sleep' remains difficult to evaluate without specialized equipment.

the sources

1. 1Senaratna CV, Perret JL, Lodge CJ, et al. 2016
2. 2Wang X, Ouyang Y, Wang Z, et al. 2013
3. 3Kaditis AG, Alonso Alvarez ML, Boudewyns A, et al. 2016
4. 4Vaucher P, Druais PL, Waldvogel S, Favrat B. 2012
5. 5Allen RP, Picchietti DL, Auerbach M, et al. 2018
6. 6Baker FC, Lampio L, Saaresranta T, Polo-Kantola P. 2018
7. 7Wang M, Lu X, Zheng X, et al. 2023