Historically, August is a dull month for dealmakers as Wall Street heads to the Hamptons and European CEOs go on holiday. But this August marked the slowest pace for mergers since 2004, according to research firm Dealogic.

Hampered by tightening credit markets, which made it difficult to borrow money to fund deals, global mergers and acquisition volume dropped 25 percent from 2006. Worldwide M&A totaled $183.3 billion, which was the slowest August since 2004 and the weakest monthly tally since July 2005, Dealogic said.

In the U.S., merger activity dropped to $53.9 billion, down 22 percent from August, 2006. This month’s deals included private equity group TPG’s $395.5 million agreement to buy Midwest Air Group and pharmacy-benefits manager Medco Health Solutions Inc.’s pact to buy PolyMedica Corp. for $1.2 billion.

On the bright side, global M&A still is up 51 percent to a record $3.6 trillion this year, compared with the same period a year ago, boosted by frenzied dealmaking in the first half of the year. Year-to-date, M&A in the U.S. is up 36 percent from last year to $1.3 trillion. 

The Dealogic statistics are current as of August 29.