Are the roots of your dreadlocks seeming a little thin? Are your dreadlocks growing thinner over time?
Normal deadlock roots themselves are going to be thinner than some might expect. The roots are going to just be normal, straight hair and it's surprising how thin those loose hairs may seem when compared to the thick rope-like dreadlock that grows out of them. So most of the time with young dreads, what may at first appear to be thinning roots is likely just to be undreaded loose root hair that's not matured tight yet.
There are two main causes for roots to actually thin out overtime resulting in the dreadlocks growing thinner and thinner over time and these are:
General hair thinning / hair lose.
It's no secret that as you get older your hair will thin, guys especially. The hair already in your dreadlocks will stay in your dreadlocks but as the hair on your head thins out, so will the roots of your dreadlock resulting in the dreadlocks becoming thinner overtime. Unfortunately there is no cure for baldness at this time so if you are losing your hair... your dreadlocks are going to thin.
The other cause of root thinning is excessive root maintenance. Working on your roots runs the risk of damaging hairs there. Any hairs that you damage are going to no longer be a part of that dreadlock and although they will continue to grow and will likely rejoin the dread again once they're long enough, the dreadlock will be permanently weaker at the maintained point. It's unlikely you'll notice much damage at the time, but since dreadlocks are a long term commitment and you usually have them for years at a time, those breakages can add up leading to thinned roots and dreads.
If you're experiencing thinning roots from maintenance I would advice to stop the maintenance - at the least reduce the frequency and take more time and exercise more caution to help avoid breakages. Try to keep the root hairs strong and healthy and not dry - this may mean avoiding salt water spray (which I don't recommend getting on your scalp anyway) and bleaching the roots. Changes in diet can also promote healthy hair growth.