I have bipolar and I was wondering if it leads to demintia?

No. Bipolar disorder and dementia are two separate and independent disease processes. Having bipolar disorder does not increase the risk of dementia.
Bipolar dementia. There is cognitive impairment associated, but it is not at the same rate or pattern because of differing mechanism of action as with other types such as alzheimer's, vascular, alcohol induced, other or even schizophrenia.
It does not. However, life long untreated bipolar often leads to a progressive decline in overall functioning. When treated properly, people with bipolar lead normal, high functioning lives.