PARIS—American Express’ consulting unit says top-tier fashionistas’ spending on luxury goods slowed in the first half of 2011, while spending by regular customers accelerated during the same period.

In a Paris press conference Thursday, American Express Business Insights’ Sujata Bathia said fashion enthusiasts—defined as the top 5 percent of spenders on luxury goods—had been driving spending on high-ticket fashion, accessories and jewelry since the 2008 economic downturn.

But their spending was down by 10 percent in the first half, while luxury purchases by general customers was up by 13 percent, compared with a year earlier.

These trends were seen across the globe, according to the study, which was carried out in the US, UK, France, Hong Kong, Japan and Australia.