US Sailing has this to say [emphasis added]:
2015. A word of caution to all persons who consider using helmets while sailing. There is no data to confirm that helmets will prevent concussions. The brain injury comes from the acceleration/deceleration from the strike, which is apparently not substantially altered by a helmet.
Helmets have been shown to reduce the incidence and severity of facial and skull fractures, contusions and lacerations but not concussions.
Concussions seem to occur more easily in pre-teen and teens. We also need to be aware that adding a helmet to a young head makes the head a “larger” target and could possibly lead to more head strikes.
Therefore, it is the position of the Sports Medicine Committee of US SAILING that helmets should be considered and encouraged but not mandated for:
♦ aggressive competitive sailing,
♦ crew positions at increased risk for strikes to the head, and
♦ sailors who are learning the sport and thus unfamiliar with the position and movement of rigging and equipment.
In the event that a concussion or head injury occurs, treatment and the evaluation for a return to activity should be done by a trained specialist.
David Jones, M.D., Chair of the Sports Medicine Committee
Thomas Hubbell, M.D., President of US Sailing
Kayakers have long worn them. In fact, it is the law in many whitewater areas, including my home Potomac river from Great Falls to Chain Bridge. It's easy to get pasted in the head by a rock while inverted.
The Protec Ace is top rated and economical. I like to for whitewater kayaking as well.
I googled ocean racing accidents. While head injuries represent only a small portion of the total carnage, they represent nearly half of the injuries resulting in evacuations or retirement. I strongly suspect they are a factor in some of the drownings ("So-and-so was knocked overboard by the boom [or spin pole, or banged across the deck] and was recovered drown.). You don't need a skull fracture to be dazed just enough to swallow some water after going in head first.
A little impractical, I think. For a helmet to prevent concussions it needs to be thick enough to provide deceleration distance.All kidding a aside, the risk of entanglement in lines and increased impact when hitting the water at speed disqualify and oversized design.
I googled cruisers. There's a good list of injuries in heavy weather. I've been tapped a good number of times, but a cap is enough for those. I did get swatted to the deck once, but it was just a skimming across the crown and did no damage. But it makes you think.
And then there is the danger of the helmet itself. I wide rim, like a bike helmet could snag on ropes. A brim could add to rotation or catch on the water at high speed. A helmet needs to be compact, such those we are seeing on many performance boat crews. I need to feel the wind. It cannot block my vision. On the other hand, it could keep my head warmer in the winter and it could double as a rain hat. Which brings up the matter of interference with the hood.
As I descend the rabbit hole of article research, I'm becoming convinced they are rational in many settings. Youth through college sailing, beach cats and skiffs, and maybe any small boat racing where mark rounding get crazy. Ocean racing in rough weather. Up the mast off-shore for everyone.
But what about cruising scenarios? The foredeck when it's bad. Perhaps it is like headlights (if the wipers are on, the head lights must be on); if tethers are needed, so is a helmet? No, that seems like too much as a general rule. On the other hand, seatbelts don't seem very useful until that one instant you need one. When I look at the numbers, including only experiences sailors, It's hard not to see PFD, tethers, and helmets in a similar light. The accident numbers say they are all in the same range. Discomfort and expense are all in a similar range, I think. You wear a hat and I'm pretty used to my bike helmet. But I do miss the wind in my hair and I don't always wear it.
Food for thought.