The major stock indexes struck fresh lows for the year yesterday as a cautious forecast from Apple Computer unsettled investors, who are growing uneasy about the economy despite signs of continued improvement in the labor market.

The Dow Jones industrial average and the Standard & Poor’s 500 sank to five-month lows, reflecting the market’s anxiety about interest rates and the economy. Following a disappointing retail sales report for March, investors seemed intent on focusing on negative news, but with earnings season just barely under way, some analysts said it was too soon to assume the worst.

“We don’t think any kind of concrete opinion about earnings can be formed yet because we’re still in the early stages,” said a market strategist at Piper Jaffray, Brian G. Belski. “We are in defensive, reactionary times, which longer term, have traditionally provided good entry points.”

The Dow slumped 125.18, or 1.20%, to 10,278.75. It was the Dow’s worst close since November 3, when it finished at 10,137.05.

The broader indexes also fell. The Nasdaq composite index shed 27.66, or 1.40%, to 1,946.71. The last time it closed lower was on October 26, when it closed at 1,928.79.

The S&P 500 declined 11.74, or 1.00%,to 1,162.05; it has not closed lower since November 4, when it stood at 1161.67.

Analysts were struck by what many characterized as a shift in the market following Wednesday’s lower-than-expected retail sales results, which ignited fears of a slowdown in consumer spending, and in turn, corporate earnings. The only thing that could ease those concerns could be upbeat forecasts for the rest of the year from market bellwethers reporting over the next few weeks. But an after-the-bell earnings miss by International Business Machines cast doubt on the likelihood of that happening.

“You haven’t heard the phrase ‘economic slowdown’ in a while. There are real questions about the strength of the economy in the second half,” said the head trader at Ryan Beck & Company, Jay Suskind. “Investors are wondering if these numbers are the best we’re going to see. It’s as if good news is bad and bad news is bad. The sentiment is one of fears and jitters, and no one wants to buy this market.”

Crude prices were volatile a day after flirting with a seven-week low. Light, sweet crude for May delivery slipped in early trading, but rebounded after falling below the $50 mark. Oil futures climbed 91 cents to settle at $51.13 per barrel on the New York Mercantile Exchange.

Apple declined 9.2%, or $3.78, to $37.26, despite the fact that quarterly profits jumped more than six-fold thanks to its iPod music players. The results soundly beat Wall Street estimates, but investors collected profits anyway amid concerns that the company might not be able to produce another blockbuster product.

IBM surprised investors by missing analysts’ estimates by 5 cents a share. The world’s top provider of computer hardware, which fell 93 cents to $83.64 in the regular session, plummeted another $3.20, or 3.83%, to $80.44 in the after-market.

Among gainers, Kerr-McGee Corporation rose 6.7%, or $4.93, to $78.90, after the oil and gas company said its board had authorized a tender offer to buy back up to $4 billion of the company’s common stock at a price between $85 and $92 per share. Separately, the company said it reached a settlement with billionaire financier Carl Icahn, certain affiliated funds, and Jana Partners LLC, who own 7.5% of Kerr-McGee collectively and were seeking election to the company’s board.

The Russell 2000 index, which tracks smaller company stocks, was down 10.60, or 1.76%, at 591.94.

Decliners outnumbered advancing issues by about 4 to 1 on the New York Stock Exchange.