Here are the biggest threats that are keeping Asian CEOs up at night

Business optimism dropped to a 3-year low in 2015.

The big bosses of companies in Asia Pacific are losing sleep over heightened volatility in global financial markets, according to PwC's latest annual APEC CEO Survey.

Only 28% of CEOs said that they are "very confident" that their company will see revenue growth over the next twelve months. This is a far cry from 46% a year ago, and also marks the lowest level since PwC started tracking 12-month confidence for Asia Pacific CEOs in 2012.

Economic concerns aren't the only trouble for CEOs. Business leaders are also worried about cyber security threats, exposure to natural disaster risks and regional geopolitical tensions, which have been named as the leading risks to business investment and growth.

“After a year of historically high foreign direct investment into developing Asian economies, APEC CEOs have become very sensitive to financial market signals and the likely impact on revenue growth,” says Dennis M. Nally, Chairman of PricewaterhouseCoopers International.

However, over half or 53% of CEOs still plan to increase investments over the next 12 months, with most of that investment planned for the APEC region.

More of the 800 APEC business leaders surveyed – PwC’s largest sample ever – point at expanded broadband access and increased participation in the digital economy as holding the most promise for their business from regional connectivity, ahead of regional trade projects or new infrastructure in underdeveloped areas of the region.

"[CEOs] are still expanding into new APEC locations. This gives testament to the experience they have gained in managing short-term instability and balancing this against the opportunities to generate business in the region,” Nally added.