Hi Mr Gaskell,
I'm sorry to hear about your dad, he is still young. The general prognosis for Lewy Body Dementia is not good. I don't know the symptoms your father is now manifesting, whether or not he has parkinsonian symptoms yet but there isn't really much help from conventional medicine.
http://www.mayoclinic.com/health/lewy-body-dementia/DS00795
Have there been others in you family who have been diagnosed with similar symptoms even if the condition was called by another name? If so, you and your dad might benefit from a change of diet to begin with.
While I don't have first hand experience with LBD, I do have some experience with Parkinson's disease and what we hope is a transient form of dementia which we are trying to balance with supplements and medication adjustments. Before the sudden onset of new symptoms which have not yet been fully diagnosed - we're eliminating causes now - I switched my husband to a gluten-free diet. (Well, as low as possible because he has a limited sense of taste and almost no sense of smell and sometimes I have to pull out an older condiment.) That seemed to help with some sleep issues but now there has been a turnaround. We may discuss a return to Amantadine as a temporary measure.
Here is a link to several other links on Gluten sensitivity. I would mention that there are many adjustments you can make in supplements and diet but remember that if you do so, you might want to discuss each with your father's physicians and most important - keep a journal.
http://jccglutenfree.googlepages.com/
We made a change last night when I simply switched the Vitamin B complex to bedtime. I think that it did make a slight difference but I am thinking that I need to add separate B2, B5 and B12. Some say to try Vitamin E therapy. Other suggestions for LBD would be essential fatty acids, antioxidants which we already use for his PD.
What I did find was an inspiring blog which I suggest you read. The writer posts regularly in journal form and has made a change in her LBD mother's diet from processed foods to gluten-free and healthy, natural foods. You will find the information in the blog more hopeful and inspiring than any other site:
http://backdoorlogic.blogspot.com/2009/12/day-insurance-company-called.html
Just navigate through the site and make notes.
There are other journals online and I think there is information that you can use here as well:
http://www.lewybodyjournal.org/
Still, you need to read mainstream information for new developments:
http://www.lewybodydementia.org/
http://www.lbda.org/feature/1942/an-introduction-to-lewy-body-dementia.htm
http://www.dementiacarecentral.com/aboutdementia/lewy
I would suggest registering at some of these sites so that you can participate in the discussion forums. You may find answers to questions you hadn't even considered as questions.
Learn as much as you can about conventional and alternative treatments of LBD because someone is going to have to discuss treatments with the doctor and doctors can often learn from patients and their families. Take printouts with you when your dad next has a doctor's appointment. Be aware of the downsides to certain meds. Some might make things worse.
Symptom manifestation can change from day to day but it is best to have a routine and a safe residential site. If your dad has trouble with balance, make sure he has at least one cane. Try different styles. Make sure there is a shower seat and a safe grab bar in the tun/shower area. The last thing your dad needs is a fall.
Look into the caregivers available so that the primary caregiver gets relief. Look into the legal aspects and make sure that you are on the list of people who can discuss your dad's medical issues with his doctors.
Because I am simply at a loss both for you and for the dementia symptoms here, I will suggest an alternative site. We've already been trying some of these as separate supplements but it will give you an idea. Read all you can read before you buy anything. Check for interactions with medications or dosage times. Supplements may be milder but they act on the body in similar ways. More often the effective ones wil be the building blocks for the needs of the body. Just make sure they are building the right things:
http://alzheimers.emedtv.com/alzheimers-articles-a-to-z-page-10.html
http://www.raysahelian.com/dementia.html
Part of your dad's medical team may need to be a geriatric psychiatrist or neuropsychiatric specialist
Don't forget the value of notes around the house as reminders for your dad for day to day tasks. The more you can help him to be independent, the better he will feel about himself. I need to take a tip from the good advice about helping the loved one to feel better about him or herself because that may actually make a subtle difference.
I apologize for the rambling nature of this answer - As I answer you, I am also caring for my husband who is currently exhibiting several symptoms of dementia.
I just found a good link for carevigers of dementia patients:
http://www.caregiver.org/caregiver/jsp/content_node.jsp?nodeid=391
You will find some excellent information at this site and it should be read by everyone in the family of a dementia loved one.