"A year ago, retired investors were three times as optimistic as working Americans and now retirees are less optimistic, which may be attributed to how challenging it is to have any kind of growth in savings. Our questions on interest rates show the impact low rates are having – they are challenging for retirement nest eggs, particularly when core inflation rate growth is about 3 percent a year and CD rates are yielding less than 1 percent. Some people may feel like they're pushing mud uphill," said Karen Wimbish, director of Retail Retirement at Wells Fargo.

Working investors say lower interest rates are good for consumers and businesses, with benefits outweighing the costs by 73 percent to 22 percent. Retirees are more evenly split, with 47 percent saying benefits outweigh the costs vs. 43 percent who do not agree.

U.S. health care costs are exorbitant, according to three-quarters of respondents, and 80 percent of all respondents said health care is in a state of crisis.

That said, nine out of 10 investors rate the quality of health care they receive as good or excellent.

Sixty-seven percent of respondents said their insurance costs increased a lot or a little, while 29 percent of working investors say rising health care costs have reduced their ability to save for retirement and forced some to delay retirement.

The May poll found that today's retirees are more likely to depend on employer-sponsored pension and Social Security for their retirement income, while future retirees expect to rely on their own savings.

Only 20 percent of working investors said that Social Security would be a major funding source for them in retirement, down from 30 percent in May 2011, and compared to 47 percent of retirees. The report also found that:

• Two in three (64 percent) of the non-retired say their 401(k) will be a major source of retirement funding for them – down from 70 percent in February, and compared to 33 percent of the retired.
• Thirty-six percent of the non-retired expect pensions to be a major funding source for retirement – up from 32 percent in February, and compared to 50 percent of retirees.
• Thirty-one percent of the non-retired call stock investments a "major source" for funding their retirement – down from 33 percent in February, and compared to 27 percent of the retired.

These findings are part of the Wells Fargo-Gallup Investor and Retirement Optimism Index, which was conducted May 4–12, 2012. The sampling for the Index included 1,018 investors randomly selected from across the country, with a margin of sampling error of +/- 3 percentage points.