Millionaire investor confidence sunk to its lowest level in seven months in April.

According to Spectrem Group, its Millionaire Investor Confidence Index fell nine points in April to minus-one, a neutral reading and the index’s lowest level since September, when the index stood at minus-six. This marks the second-consecutive monthly decline for the index, following an identical nine-point decline in March.

Meanwhile, the Spectrem Affluent Investor Confidence Index, which measures the investment confidence and outlook of households with $500,000 or more in investable assets, fell eight points in April to minus-seven, also a neutral reading.

“Millionaires’ investment confidence fell for a second-straight month in April, suggesting some level of concern about the strength of the economic recovery,” said George H. Walper, the president of Spectrem Group. “This decline brought millionaires’ confidence to its lowest level since September 2010, as optimism among the broader affluent population also fell. Millionaires and the affluent both expressed concern about the economy and stock market conditions in April, with retirement also ranking as a key factor affecting their investment plans.”

In response to an open-ended question about the one factor most affecting their investment plans, affluent investors in April cited: the economic environment (24%); stock market conditions (22%); household income (12%); retirement (7%); housing and real estate (4%); and the political climate (1%).  Those citing the economic environment rose from 22% in January 2011, the last time this question was asked, while those citing stock market conditions fell from 25%.

Millionaires were more focused on the stock market conditions (25%) than the affluent but slightly less focused on the economic environment (22%).

The Spectrem Affluent Investor Confidence Index is based on 250 monthly interviews with the financial decision-makers in households with $500,000 or more in investable assets.  The Spectrem Millionaire Investor Confidence Index is based on a subset of the overall survey group.