After almost three decades helming Suzuki Motor Corp., investors are becoming increasingly concerned at the lack of clarity over who will succeed the carmaker's octogenarian chairman and president.

At 84, Osamu Suzuki has already beaten the average life expectancy for men in Japan by four years. His term was extended by one year at the annual general meeting Friday in Hamamatsu, Shizuoka Prefecture.

"It's a big risk having an 84-year-old at the helm and there's a widespread sense of uncertainty," said Kazuyuki Terao, Tokyo-based chief investment officer at Allianz Global Investors Japan Co. "We're most concerned that if Osamu leaves suddenly given his age, the market will react negatively without knowing what comes next."

While Suzuki earned a record profit last year, its revenue is dwarfed by automakers like Toyota Motor Corp., undermining its ability to keep up with spending on research and development. Investors such as Mizuho Asset Management are also concerned about the carmaker's strategic direction after Suzuki leaves.

While he hasn't designated a successor, Suzuki promoted four of his lieutenants in 2011 to the level of executive vice presidents, from which a president may eventually be chosen. They include his son, Toshihiro Suzuki, 55, who heads the company's overseas business.

The other three executive vice presidents are Yasuhito Harayama, 58, who used to work at the Ministry of Economy, Trade and Industry, and veterans Minoru Tamura, 66, and Osamu Honda, 64.

"It's not transparent," said Takashi Aoki, a fund manager at Mizuho Asset. "We don't know what to expect. That's not good for investors."