In fact, the Hadza people of Tanzania, a group of nomadic hunter-gatherers, sleep an average of 6.25 hours per night.
Adequate sleep leads to a stronger immune system, better metabolic and cardiovascular health, and more reliable physical energy throughout the day.
However, it remains unclear whether abnormal sleep is a causal risk factor or an early symptom of cognitive decline.
The evolving consensus points toward a vicious cycle in which inadequate sleep contributes to dementia, which in turn makes sleep worse.
These wedged-in activities reduce my sleep quota, but are also proven to help sustain a healthy body and sound mind.
Some historians believe that before widespread electric lighting allowed us to be up all hours, humans most likely spent more time in bed. But those hours may have been less rigidly consolidated, with greater seasonal variation and more segmented patterns — perhaps an hour or so in the middle of the night to pray, read, talk or do quiet tasks.
In fact, the Hadza people of Tanzania, a group of nomadic hunter-gatherers, sleep an average of 6.25 hours per night. Although in bed for up to nine hours, the Hadza are routinely awake for two or more hours during that window.
All of this is not to undermine sleep as a powerful and healthy habit. Sleep improves performance on tasks, makes driving safer and buoys our mental health. Adequate sleep leads to a stronger immune system, better metabolic and cardiovascular health, and more reliable physical energy throughout the day.
One of the most concerning findings about not getting enough sleep comes from the Whitehall II study, which found that persistent short sleep duration (defined as less than six hours) at ages 50, 60 and 70 was associated with a 30 percent increased dementia risk compared to normal sleep duration (defined as seven hours). However, it remains unclear whether abnormal sleep is a causal risk factor or an early symptom of cognitive decline. The evolving consensus points toward a vicious cycle in which inadequate sleep contributes to dementia, which in turn makes sleep worse.
Nonetheless, I usually find myself going to bed later than I intend. Squeezing in a full day of doctoring, parenting, exercising, cooking and sitting down for a family dinner feels worth it to me. These wedged-in activities reduce my sleep quota, but are also proven to help sustain a healthy body and sound mind.
Hippocrates himself wrote: “Both sleep and insomnolency, when immoderate, are bad.” It turns out this warning about too little and too much sleep holds up surprisingly well in the modern scientific literature over 2,000 years later.
As a family physician, I must balance biological, psychological and social considerations when I care for patients. Here’s what I tell them: Aim for seven hours, accept that some people need more or less to feel rested, be compassionate with yourself about sleep failures and realize that there are times when it’s worth it to shoehorn in a bit more conscious life from a day.
