Merge branch 'master' of https://github.com/hello-nyxo/nyxo-website

content/blog/what-can-heart-rate-tell-about-your-sleep/index.md

@@ -18,15 +18,15 @@ If your night-time heart rate scores higher than usual, it is more than likely y
 
 #### Mental Overload
 
-Stress, alertness, and emotional or cognitive overload are among the most typical causes of sleeping troubles. In these cases, something in your life or surroundings (be that work, relationship worries, or video games) activates fight or flight reaction in your body. Your heart rate gets high, stress hormone levels elevated, and your whole body alerted. As useful as this may be in some situations, in the evening-time, it makes falling asleep very difficult and severely disrupts your sleep. Unusually high heart rate at the beginning of the night might indicate mental overload.
+[Stress, alertness, and emotional or cognitive overload](https://nyxo.app/lesson/difficulty-falling-asleep) are among the most typical causes of sleeping troubles. In these cases, something in your life or surroundings (be that work, relationship worries, or video games) activates fight or flight reaction in your body. Your heart rate gets high, stress hormone levels elevated, and your whole body alerted. As useful as this may be in some situations, in the evening-time, it makes falling asleep very difficult and severely disrupts your sleep. Unusually high heart rate at the beginning of the night might indicate mental overload.
 
 #### Physical Overload
 
 Physical overload can have similar effects as mental overload. Overtraining is a state that occurs if a person exercises so hard that they exceed their body's ability to recover. Elevated night-time heart rate is one of the signs telling the body isn't able to recover from the exercise even over the night. Working out too late in the evening may have similar effects if the body hasn't completely recovered from the physical activity before going to bed. This may be an issue, especially for older persons, since their bodies often need more time to recover from exercise than younger people.
 
 #### Chemical Substances
 
-Alcohol, nicotine, and caffeine can all elevate your heart rate during the night and disrupt your sleep.
+[Alcohol](https://nyxo.app/lesson/alcohol-myths-and-facts), [nicotine](https://nyxo.app/lesson/how-nicotine-affects-your-sleep), and [caffeine](https://nyxo.app/lesson/addicted-to-caffeine) can all elevate your heart rate during the night and disrupt your sleep.
 
 #### Sickness