It continues to be unclear how June's surprise Brexit vote will affect the rest of the world economy.

While the US economy and its companies have limited direct exposure to the UK, the resulting uncertainty could have substantial indirect effects as financial markets go haywire and consumer sentiment goes south.

Citi hardware analyst Jim Suva just cut his forecast for Apple (AAPL) earnings, blaming the Brexit vote among other things.

"We are lowering our estimates for June and September quarters given potential for lower demand from macro uncertainty (Brexit related), currency volatility and lengthening replacement cycles," Suva wrote in a new note to clients.

Regarding the replacement cycle, Suva estimated that the average rate of replacement has increased to 30 to 36 months, up from around 28 months more recently. In other words, iPhone users are waiting an extra two to eight months before upgrading their iPhones.

As for the impact of Brexit, it may seem like a stretch that it alone could be a major source of trouble for Apple. However, growth comes at the margin. And when you consider all of the folks on the fence about making a major purchase like an iPhone, heightened uncertainty from something like this unprecedented Brexit vote is more likely to put the consumer on hold.

Suva estimates that Apple sold 40.3 million iPhones in the second quarter. Overall, he sees Apple reporting revenue of $41.2 billion and earnings per share of $1.35. He has a Buy rating on the stock and a price target of $115.

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Sam Ro is managing editor at Yahoo Finance.

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