CUPERTINO, Calif:

Apple Inc introduced its largest-ever iPhone and a watch that detects heart problems on Wednesday in an attempt to get customers to upgrade to more expensive devices in the face of stagnant global demand for smartphones.The relatively small changes to its lineup, following last year’s overhauled iPhone X, were widely expected by investors and the company’s shares ended down 1.2 percent at $221.07.

The strategy has been successful, helping Apple’s stock to rise more than 30 percent this year and making it the first publicly traded U.S. company to hit a market value of more than $1 trillion.

This year’s three top phones are all more expensive than last year’s models.

With two of them starting at $999 or higher in the United States, Apple appears to be taking advantage of a strong U.S. economy, low unemployment, and rising household wealth.

The median U.S. household income rose for a third straight year in 2017 to the highest on record since 1967 by one measure, government data showed on Wednesday.It is positioning the new watch as a more comprehensive health device, able to take an electrocardiogram to detect an irregular heartbeat and start an emergency call automatically if it detects a user falling down, potentially appealing to older customers.

The U.S. Food and Drug Administration said it worked with Apple to develop apps for the Apple Watch and has been taking steps to ease the regulatory pathway for companies seeking to create digital healthcare products.

As many as 6.1 million Americans have atrial fibrillation, a heart disease involving irregular heart rhythm for which the Watch could offer an early warning. That number is expected to double by 2050 as the population gets older, according to the American Heart Association.

“This does have a lot of potential for patients,” said Dr. Michael Valentine, president of the American College of Cardiology and a cardiologist at Central Health in Lynchburg, Virginia. “Clinicians face patients every day with palpitations, rapid heart rates, and other symptoms,” and the doctors want a more portable monitoring and recording system.

BMO Capital Markets analyst Joanne Wuensch added that physicians would be unlikely to make medical treatment based on data from the watch, though it could encourage patients to see cardiologists.

Healthcare technology analyst Ross Muken at Evercore said many companies were developing monitoring devices. “This update really establishes the company’s increasing efforts to push the watch as a serious medical device,” he said of Apple.