How important is it to get a firm diagnosis of dementia?

I think your question is very important, though I do not have a personal answer. I know knowledgeable people will jump in. I did find an Aging Care article (can't verify the date it was written maybe it was Dec. 15, 2017?):

https://www.agingcare.com/articles/early-diagnosis-of-alzheimers-disease-151217.htm

I am dealing with the inverse of your situation. Five years ago my husband's PCP blurted out that he had "vascular dementia" -- that's with no tests, no interview, no record of anything. PCP blurted it out and it seemed he was lightly joking (because my husband had asked a question about not being able to read the way he used to (quite the scholar). In my opinion, my husband hadn't changed at all (Ph.D. in clinical psychology and spoke at a very high comprehension level to his PCP). Of course, that "diagnosis" has remained in his record ever since. I believe the "diagnosis" is now causing problems.

My take, from what I read, is that if you decide on getting a diagnosis, go to a geriatrician and/or a neurologist who specializes in geriatrics. I'll be watching for more knowledgeable answers.

I am so sorry your family is possible facing a very bittersweet walk with your sister. It sounds like you are very sensitive to her, and she is lucky. Take care, especially through the stress of holidays and people pulled in a zillion directions.

I think it's very important. There are many physical and mental ailments that can cause cognitive decline. Many of them can be treated. For example, low thyroid hormone can cause memory problems. Thyroid medication can fix it.

Your sister shouldn't suffer with confusion and bad memory if all she needs is better nutrition or a supplement of some sort. Get her to go to the doctor.

It can be very important or not at all it depends on the stage and the disease.
My Husband was "diagnosed" with Alzheimer's. Later I was convinced that he had Vascular Dementia...possibly both. But by that time I figured it would be more traumatic to get an accurate diagnosis as knowing he had one or the other or both would NOT change the treatment nor the outcome.
A person diagnosed with LBD (Lewey Body Dementia) can become violent and there are particular medications that can be fatal to someone with LBD.
Early stages there are medications that might or might not work. But at least you can make an informed decision as to the course you want to take. And there are also clinical trials that might or might not work if the person is qualified and most start with an early diagnosis.
But "official" diagnosis there are other factors..is this person still driving? Once there is an official diagnosis I think it is irresponsible to let the person continue to drive and once there is an "official" diagnosis if there is an accident of any kind there may be problems with insurance. Is this person still working? If so at what point to you "retire" do you tell coworkers?
Do you continue to let this person handle their finances? In this respect it is important to know what will be necessary...
See an elder lawyer get all the papers drawn up that will be needed to protect their assets so that they can be used to pay for care that will be needed in 6 months?, 1 year?, 2 years?......
Discuss with them now, and this is a good conversation to have with and for ALL family members what do they want to have happen when they can not ..care for themselves, eat, drink, We should all have this discussion with family members.

As Marcia 7321 indicated, several conditions can mimic dementia, but are treatable and should be treated.

Yet, even if dementia is present ... additional, treatable conditions that make symptoms more severe may also be present. These, too, should be diagnosed and treated.

My FIL is definitely in the early-moderate stages of dementia. So far, both he and my MIL refuse a full workup for him (...g-r-r-r-r-r...). Hence, there is no specific diagnosis.

Still, over the past few years he's experienced several periods of sharp decline which, when diagnosed, were reversed (at least to some degree) after proper treatment. Thus far, his temporary issues have involved infections, respiratory illnesses, sodium deficiency, medicine interactions and aggravated congestive heart failure.

Treatments have helped him hold on to some cognitive functions he would have lost completely before now, preserving quality of life.

But, dementia is a journey that leads to one place. We may be approaching (or have reached) the point where treatments can no longer slow his decline.

Your sister, however, may not even be suffering dementia. She deserves to have all treatable conditions ruled out, or diagnosed and treated. Even if it turns out that dementia is also present.

Best Vibes!

You might want to ask your sister to get a diagnosis of her health issues for her sake and for the rest of the family's sake. If she has some other treatable condition, then it should improve her outlook on life. If she does have the beginnings of dementia (of any form), it is good to know so that you can plan for what needs to be done to protect the patient (your sister), including legal documents, health care proxies, etc. Does she have a LTC policy? Whoever may eventually be responsible for taking care of your sister might be the best person to push your sister towards looking after her own health.

It is important to find out.  There are many simple things that can effect a persons cognitive abilities that are easily treated.  The Dr. can rule out all of those things first.  Second, there are medications that will slow the progress of dementia.  The earlier you start on them the better.  Get checked out.

happyjack - you did not indicate your sister's age or living arrangements. Although someone can develop dementia at a young age (there is a woman in mom's MC unit that is not quite 60!), there can be other reasons for her condition. Does she live alone? Can she manage ADLs? Has she ever been diagnosed/treated for depression? If she is living alone, can you either get her to move in for an extended "visit" or have someone stay with her to monitor her in her own place?

I do concur with several others that there can be MANY medical conditions that can make it seem like someone has dementia, but in reality it is not. Once the condition is treated, the dementia-like symptoms can go away. Has she had any surgery recently? That can also contribute. Depression alone can cause many issues, and sleep issues can contribute even more, compounding the depression.

She should have a FULL medical evaluation to determine what might be going on and get treatment if possible. I can say from experience that several years before our mother developed dementia, (she is now 95, in MC for almost 2 years now) I happened to stop by and found her in quite a befuddled state. I took her to the ER and she was admitted, the problem being related to electrolytes. Low potassium can affect the brain big time and result in confusion, among other things. She was really out of it! In her case, being told to drink more because of supposed interstitial cystitis, she was drinking TOO many fluids and the result was watering down her system (yes, you CAN drink too much!) After about 2 days (mainly given IV fluids to replenish what was lost) she returned to being her usual nasty self, demanding to go home and being rude to me! I also heard so many times from her that the doctors treating my dad (open heart surgery) "gave" him dementia - not knowing a whole lot about dementia back then, I still didn't buy it - he was already showing signs. Now that I had to "arm" myself to take action for mom, I am aware that anesthesia alone can mimic or make dementia worse the older you are! Often the person will revert back to the state they were in before surgery, but sometimes if dementia is involved they may not regain everything. Also I can concur with other reports that a UTI can cause dementia-like symptoms or make dementia worse! We had to get anti-anxiety for mom, as needed only when these "incidents" happen (so far only once, but she was in quite a state!), and continue it's use nightly until the UTI subsided! She has not really needed the meds since resolving the UTI.

So, a complete medical evaluation should precede any guess that she has dementia. Hopefully someone has medical authority for her if she will not cooperate with getting evaluated. If they can rule out everything (PCP might not be enough to do all that is needed, you may need specialists to do a complete evaluation of everything, but PCP is a start for baseline testing), then you can explore whether there is dementia going on. It is also VERY important to determine the cause of the dementia if that is what the diagnosis is. Dementia is a big umbrella over many types of cognitive decline (Alz, vasular, LBD, fronto-temporal) and each one has it's own path and treatment options (sometimes nothing, but as others indicated, some meds are big NO-NOs for certain dementia forms!)

When I kept complaining to my therapist about my husband's forgetfulness, he suggested that my husband be tested.
Lo & behold, he had some impairment. We went to our family Dr who sent us to a geriatric specialist who treats these problems. At first, he was given a diagnosis of vascular dementia. This diagnosis allowed me to realize he did have a problem & to give him some slack. It allowed me not to insist he give the true story without rearranging the facts & I was able to allow myself to relax & go with the flow.
This year & 3 annual repeats of the test showed he did not have dementia but had vascular cognitive impairment.
The difference being mainly that dementia does not reverse itself. It always gets worse. But with VGI, there's still memory loss but there are ways to improve his memory.
Is a definite diagnosis necessary? Maybe not if your willing to live with your suspicions. But, it could be something treatable. Getting a definite diagnosis is very important for you & your sister. It'll give you & your family peace of mind but, most importantly, it'll give her peace of mind & tools to help her & you.
When the initial diagnosis came, my husband was relieved. We were no longer guessing he had a problem but now we knew what to do about it. He worked with the doctor on ways to help his memory. The doctor told us that, by following their suggestions & improving his memory, they were able to make a more correct diagnosis with a better outcome.

I have wondered this about my mom. She asks same thing over and over yet as her own MD told me and I agree, she has always done this as she is very OCD, anxious, doesn't listen, so asks same question a lot as she never listens the first time. Though now her MD is wondering if this OCD/anxiety is masking cognitive issues. She has tried to run my mom through one of those short screening tests and my mom throws a temper tantrum and will not do it. Her doc doenst know what to do

We lost my dad earlier in the year from ALZ so to be frank I am not eager to find out my mom has dementia now too, and wonder if it really matters? Not like a cancer you can do things to prevent or stop early.

I would like to see her get an medical workup. I had low B-12 and I was very confused. One pill a day is like a miracle for me. I also have to watch my Thryoid because if I let it get too low I have a lot of confusion.

Awwww so very sad , I just dont know I think I would go to dr. Appt .with her and just be honest God Bless you !!!your sister is lucky to have you!

It is important to have dementia diagnosis confirmed. There can be several treatable causes in addition to those not very treatable. Either way, those treatable causes can be addressed and resolved. Those not so treatable can be made more tolerable both for the patient and the family. Forewarned is forearmed, so if actually true Alzheimer's or a related incurable dementia, you will know what to expect and make plans accordingly.