Age makes a big difference in qualifying for SSDIB. Those who apply and are under 50 years old will have a much tougher standard to meet. If you are deemed capable of sedentary work (sit down for the majority of the work day with some standing and limited lifting capabilities) you will not qualify for SSDIB, if you are under 50 years old.
If you are over 50 years old and under 55 years old, and limited to sedentary work, the odds get a bit better but it then depends on your education (high school or greater) and any transferable skills you have acquired throughout your work career.
If you are between 55 and 60 years old, the standards are even easier to qualify for SSDIB.
People are under the mistaken assumption that once a person can no longer perform the job they have worked on for years, then they would be eligible for SSDIB. That is clearly not the case. As mentioned above, a number of factors needed to be measured together to determine your eligibility for SSDIB.