Grow Youthful: How to Slow Your Aging and Enjoy Extraordinary Health
Grow Youthful: How to Slow Your Aging and Enjoy Extraordinary Health

Are you an early bird or a night owl?

Your chronotype affects your health

Missing out on natural sunlight


Your chronotype is the time of the day (ranging between morning and evening) that you prefer for your daily activities. Most people rise within an hour of 7am, and go to bed within an hour of 11pm, getting a total of seven hours in bed each day.

Our chronotypes tend to shift earlier as we age - in middle age we may wake up and go to sleep an hour earlier than we did in our 20's, and in old age yet another hour earlier. (10)

Taking account of your internal body clock is vital for your health, and also for your optimal physical and mental performance. Research has shown that there is a best time of day to eat, think, work, exercise and sleep.

Long-lived and healthy people also have regular daily habits. They wake at the same time every morning and go to sleep at about the same time every evening. They eat their meals at the same time every day. Their activities and exercise fit into a regular daily schedule, weekends included. Trying to catch up with sleep over the weekend is not a good idea. Regularity of sleep, seven days a week, is important.

Your chronotype affects your health

Several studies show that people with a later chronotype (those who describe themselves as an evening person) have an increased risk of a variety of diseases. If you go to sleep well after midnight and rise correspondingly later, you are at a significantly higher risk of death and many other diseases.

According to a large 2018 study in the UK that included 433,268 adults aged 38-73, definite evening type people have a 10% increased risk of all-cause mortality compared to definite morning types. Those with a later chronotype and later timing of sleep have an increased risk of:

It is important to note that a 10% increase is a relative increase. The actual risk of dying in any given year is small. Less than 2% of the people in the study died during the study period, which averaged six and a half years for each participant.

These findings still held even after they were adjusted for age, sex, ethnicity, smoking, body mass index, sleep duration, socioeconomic status and co-morbidities.

Other studies have also associated later chronotype (evening preference) and later timing of sleep (which is associated with later chronotype) with morbidity, including higher rates of metabolic dysfunction and cardiovascular disease (2, 3, 4, 5) and psychiatric symptoms. (6, 7, 8)

In the 2017 Biobank Study in the UK, a large prospective cohort study, a preference for evening was also associated with more cardiovascular risk factors, such as higher rates of smoking and overweight / obesity. (9)

In a study conducted in 2012, twenty four healthy participants had their sleep shifted by one hour each day. After just three weeks, their resting metabolic rates dropped 8% and they started to look pre-diabetic. "Assuming no changes in activity or food intake ... that would translate into 12.5 pounds increase in weight over a single year," said the lead author. (11)

Missing out on natural sunlight

People who are asleep early and mid-morning miss out on morning sunshine. Their initial dose of sunlight is later than it should be, and the total hours of sunshine are fewer. Circadian rhythm and hormone production may be disrupted. Humans generally evolved to be awake during daylight hours, but nowadays bright electric lights, TVs and other electronic screens tell our bodies that it is time to be awake when we should be sleeping.

Here are some tips on sleeping really well and getting over insomnia.

Read Grow Youthful's take on sunlight and vitamin D.


1. Kristen L. Knutson, Malcolm von Schantz. Associations between chronotype, morbidity and mortality in the UK Biobank cohort. Chronobiology International, The Journal of Biological and Medical Rhythm Research. Published online 11 Apr 2018.

2. Reutrakul S, Knutson KL. Consequences of circadian disruption on cardiometabolic health. 2015. Sleep Med Clin. 10:455-68. doi:10.1016/j.jsmc.2015.07.005.

3. Merikanto I, Lahti T, Puolijoki H, Vanhala M, Peltonen M, Laatikainen T, Vartiainen E, Salomaa V, Kronholm E, Partonen T. Associations of chronotype and sleep with cardiovascular diseases and type 2 diabetes. 2013. Chronobiol Int. 30:470-77.

4. Yu JH, Yun CH, Ahn JH, Suh S, Cho HJ, Lee SK, Yoo HJ, Seo JA, Kim SG, Choi KM, et al. Evening chronotype is associated with metabolic disorders and body composition in middle-aged adults. 2015. J Clin Endocrinol Metab. 100:1494-502. doi:10.1210/jc.2014-3754.

5. Koopman ADM, Rauh SP, Van T, Riet E, Groeneveld L, Van Der Heijden AA, Elders PJ, Dekker JM, Nijpels GBeulens JW, et al. The association between social jetlag, the metabolic syndrome, and type 2 diabetes mellitus in the general population: the new hoorn study. 2017. J Biol Rhythms. 32(4):359-368. doi:10.1080/748730417713572.

6. Jankowski KS. Morningness-eveningness and depressive symptoms: Test on the components level with CES-D in Polish students. 2016. J Affect Disord. 196:47-53. doi:10.1016/j.jad.2016.02.015.

7. Melo MCA, Abreu RLC, Linhares Neto VB, De Bruin PFC, De Bruin VMS. Chronotype and circadian rhythm in bipolar disorder: A systematic review. 2017. Sleep Med Rev. 34:46-58. doi:10.1016/j.smrv.2016.06.007.

8. Putilov AA. State and trait-like variation in morning and evening components of morningness-eveningness in winter depression. 2017. Nord J Psychiatry. 71:561-69. doi:10.1080/08039488.2017.1353642.

9. Patterson F, Malone SK, Grandner MA, Lozano A, Perkett M, Hanlon A. Interactive effects of sleep duration and morning/evening preference on cardiovascular risk factors. 2017. Eur J Public Health.28(1):155-161.

10. Dorothee Fischer, David A. Lombardi, Helen Marucci-Wellman, Till Roenneberg. Chronotypes in the US - Influence of age and sex. PLoS ONE 12(6): e0178782. Published 21 June 2017.

11. Orfeu M. Buxton, Sean W. Cain, Shawn P. O'Connor, James H. Porter, Jeanne F. Duffy, Wei Wang, Charles A. Czeisler, Steven A. Shea. Metabolic Consequences in Humans of Prolonged Sleep Restriction Combined with Circadian Disruption. Sci Transl Med. 11 April 2012. 4(129): 129ra43. doi: 10.1126/scitranslmed.3003200.