A group of bipartisan senators are asking the Trump administration to show support for curing and preventing Alzheimer's disease by increasing funding for research.

In a letter made public Thursday, they urged President Trump to demonstrate his support by bolstering the funding request for Alzheimer's in his fiscal 2019 budget request expected in March.

Funding would be distributed to the National Institutes of Health, which awards grants for medical research. NIH spends about $640 million a year on research. In comparison, the U.S. spends $259 billion a year caring for people with Alzheimer's, including $175 billion for government-funded Medicare and Medicaid.

Alzheimer's is the sixth-leading cause of death, and its numbers are rising as the baby boomer generation ages. No effective prevention, treatment, or cure exists.

"Although we have made progress in increasing funding, Alzheimer's research funding remains disproportionately low compared to its human and economic toll," the senators wrote in a letter to Trump.

They noted noted that a bill passed in 2010, the National Alzheimer's Project Act, set a goal to prevent and treat Alzheimer's by 2025. Senators didn't request a specific funding amount from Trump, urging him instead to "support efforts to meet the research investment objective" that was laid out in the 2025 plan. To achieve that goal, they signaled higher investment would be necessary.

Alzheimer's advocates have urged a $2 billion funding goal, noting that other diseases receive significantly more investment from the federal government. Cancer, the second-leading cause of death in the U.S., receives nearly $5 billion in funding a year. HIV receives more than $3 billion a year.

The 15 senators, including Susan Collins, R-Maine, and Amy Klobuchar, D-Minn., said that such funding levels had paid off.

"Investments in research and other diseases have yielded tremendous results: patients have access to new treatments, and death rates for some diseases are decreasing," they wrote. "Yet, at the same time, mortality due to Alzheimer's is escalating dramatically."

Trump's father had Alzheimer's disease, and during his campaign he called it a "total priority for me." He didn't specifically mention Alzheimer's disease in his budget request last year, but proposed $5.8 billion in NIH cuts. Congress ultimately decides funding allocations, but a president's budget demonstrates the administration's priorities.

The current bill in Congress to fund the government, which hasn't been passed, would increase funding for Alzheimer's by $414 million, bringing the total close to the $2 billion urged by advocates.