US millionaires' investment confidence falls in Oct

* Millionaire index down 2 points to -7

* Affluent household index down 2 points to -15

* Stock market conditions biggest investing concern

NEW YORK, Nov 4 (Reuters) - Even for millionaires, life is not an eternal walk on Easy Street.

U.S. millionaires worried more about money in October than September, according to a survey released on Wednesday.

The Spectrem Group said its millionaire confidence index fell 2 points to -7 in October, marking its first decline since July.

U.S. stock markets have been on a steady rise since hitting 12-year lows in March, with the S&P 500 .SPX index up 50 percent since March.

The U.S. millionaire population in 2008 fell by 2.5 million to a five-year low of 6.7 million, as the financial crisis hit real estate and stock prices, Spectrum reported in March.

Spectrem's survey of affluent households with $500,000 or more of investable assets also showed falling confidence in October, with the confidence index down two points to -15, keeping it in bearish territory.