24 is a local minimum for death rate in the U.S.. On your 24th birthday, you are less likely to die in the next year than if it were your 21st, 22nd, or 23rd birthday, or any subsequent year for the rest of your life. The absolute most survivable year is age 11, before which congenital illnesses and underdeveloped immune systems make children die at higher rates. Between 12 and 23, increasing access to dangerous activities and substances combined with a still developing brain give a very high spike in deadly accidents or unintentional overdoses. This is centered on 18 years, which is when American youth are granted a ton of new rights and responsibilities. Combined with the incrementally increasing risk of age related disease that indeed starts from conception, 22 year olds are particularly vulnerable to death among young adults. The site you found might be trying to sell you life insurance.