By John Miller and John O'Donnell

ZURICH/FRANKFURT (Reuters) - An unusual number of suicides by top executives in Switzerland has prompted introspection in its business community over how senior managers are dealing with stress as its companies struggle to retain their status in the global economy.

The death last week of the former chief executive of Zurich Insurance, Martin Senn, came less than three years after the insurer's finance chief, Pierre Wauthier, took his own life.

Wauthier had blamed pressure from the company's then chairman Josef Ackermann in a suicide note, although Ackermann was cleared in a subsequent investigation.

Acquaintances of Senn, 59, said he had been withdrawn since he was ousted from the company late last year, though few details of the circumstances that led to him shooting himself at his family home in the upmarket Alpine resort of Klosters have emerged.

Martin Naville, chief executive of the Swiss-American Chamber of Commerce, said the business circles where Senn and Wauthier once moved had been left shocked, pondering what could have been done to prevent the tragedies.

"The only thing you can do is to be more attentive to signs," Naville said.

He knew Senn, who was president of the chamber, as well as Wauthier, who had British-French dual citizenship. He also knew Carsten Schloter, the German-born head of telecoms group Swisscom, who took his life in 2013, and Alex Widmer, head of bank Julius Baer, who committed suicide in 2008.

Their deaths contrast with the picture postcard image of Switzerland as one of the world's wealthiest and most stable countries.

Switzerland's overall suicide rate is below the global average, roughly in line with countries such as Germany, according to the World Health Organisation.

Naville said he saw nothing in Swiss executive culture to explain the deaths. "Every case can be very different," he said. "Human beings are so complicated."

But others describe a generation of managers caught between highly demanding international investors and Switzerland's conservative traditions.

"If you fail, you are expected to excuse yourself from the conversation and drop any further ambitions. You're not expected to show your face again," said Susan Kish, a former UBS banker who has started a number of businesses, including an entrepreneurship network in Zurich.

PROXY FOR SWISS ECONOMY

Switzerland has been hit in the past few years by a slowing global economy and a strong franc currency that has hurt vital exports.

Zurich Insurance mirrors many of the challenges and is now in the throes of restructuring as it slashes thousands of jobs.

"Zurich (Insurance) is a proxy for the Swiss economy," said Stefan Michel of Swiss business school IMD.

"Switzerland is no longer an island," he said. "The pressure from global shareholders and regulators is increasing. Whenever I ask people in the financial sector how they feel, they answer: 'I am tired'."

    Staid for most of its nearly 150 years, Zurich Insurance rose to prominence in the 1990s with a series of takeovers. But its fortunes turned in 2001, when the Sept. 11 attacks in the United States left it with heavy losses, while runaway expenses at its headquarters hit the bottom line – and shareholder trust.

It underwent an overhaul before Senn was appointed CEO of Zurich in 2010.

Its chairman from 2012, Josef Ackermann, formerly Deutsche Bank's CEO, was pushing management to abandon its conservative course, people familiar with the matter have told Reuters, and take more risks on its investments to bolster returns.

Ackermann resigned after Wauthier's suicide note suggested he had been driven into a corner by the chairman, who was later exonerated in an investigation.

Senn is remembered fondly by employees who spoke to Reuters as someone who knew staff by name and shook hands with everyone at meetings, regardless of rank.

But after a series of profit warnings and an aborted takeover attempt for British rival RSA <RSA.L>, he was pressured out by the company's Dutch chairman Tom de Swaan last year.

Reinhard Sprenger, an author and management consultant who has advised top Swiss firms, said corporate setbacks, with the near collapse of bank UBS during the financial crisis and the bankruptcy of airline Swissair, have jolted the country.

"The Swiss were once supremely self confident ... that has changed and they have come back to earth."

The annual economic conference in the Swiss resort of Davos, one of the top gatherings for the world's policymakers and business leaders, has become shorthand for a new generation of driven managers who put their corporations above national interests, said James Breiding, author of a book on how Switzerland became successful.

"Like Japan, Switzerland had a strong sense of community and egalitarianism. In the last 20 years, we've seen the emergence, however, of the 'Davos man,'" he said.

"Those men that embraced the Davos scepter found themselves in an increasingly lonely club."

(Additional reporting by Michael Shields; Editing by Susan Fenton)