The Silver Fox knows.

Question 1: 

Why does hair go Grey?

Grey hair is a result of decreased Melanin (the colour pigment) in the hair shaft. 

Melanin is what changes our skin colour and our hair colour. Melanin deposition in hair is partially genetically determined, but melanin is also affected our environment, our health & other hormonal communication. 

Melanin is a pigment that is stimulated by a hormone called Melanin Stimulating Hormone (MSH).

When our stress regulation pathway is triggered, a pre-hormone called Pro-Opio-Melanocortin (POMC) is formed. 

POMC turns into two very different hormones: 

MSH is one of them, the other is Cortisol (a major hormone that helps us deal with stress). 

When our bodies shift toward a acute high stress, that pathway could shift toward making more Cortisol rather than Melanin for a short time.  Hence why some people develop grey hairs after a stressful period in their lives.

Alternatively, it could also shift toward Low Cortisol & High Melanin - which is what occurs in some pregnancies - when we see the "Mask of Pregnancy" (Chloasma), and hair getting darker during pregnancy. 

The THRESHOLD that triggers either of these situations, and the enzymes is genetically determined, but our own work at learning stress management skills with proper nutrition & health to convert hormones properly is also a determinant.

Question 2:

What role could lack of good sleep play when more hair than usual falls out?

Proper sleep allows for normal circadian rhythm of cortisol (rising just before waking & gradually  declining until we feel tired). As well, sleep is a time when Melatonin (commonly know as the jet lag hormone, not Melanin from the answer above) & Growth Hormone are at their highest.

These hormones are vital in healthy blood sugar management, post-stress recuperation, proper cell turnover and nourishment for hair growth. If we aren't getting proper sleep, these hormones are not able to function to their best capacity, which could cause hair to lose it's integrity, lustre, and possibly even it's attachment to the hair follicle.

If your hair is falling out, it could indicate many other situations though (nutrient deficiency, hormone imbalance, immune dysfunction or infection) so make sure to have someone look at your whole story, not just sleep. Rarely is lack of proper sleep the main cause of hair loss.

Question 3:

Is there anything men can do to slow down genetic hair loss?

Purely genetic hair loss, in general is not alterable. But often hair loss occurs from a myriad of causes.

Male (or Female) pattern balding, can be due to overactivity of an enzyme, or overproduction of certain hormones. Dihydrotestosterone (DHT) seems to be the hormone responsible for hair loss from the top of the head, and hair growth on the face and body.

DHT forms when testosterone is converted by an enzyme called 5-alpha-reductase (5-a-R). Some people have highly active 5-a-R, creating high DHT levels. DHT triggers the body to turn off head hair follicles and increase body hair follicle growth. The reason for this enzyme increase is unknown. Sometimes genetics plays a role, and sometimes environmental hormone influences are significant, sometimes over active stress response will enhance 5-a-R activity.

There are a few herbs and prescriptions that have been shown to help manage these, but since they alter hormone profiles, it is unwise to treat them without testing & monitoring specific hormones, and having a physician who understands these hormone pathways well.