(CNN) -- Nancy Reagan is recovering from a number of broken ribs sustained in a fall in March, a representative for the former first lady said.
Reagan, 90, was unable to attend a speech given Tuesday evening by House Budget Committee Chairman Paul Ryan, R-Wisconsin, at the Reagan Presidential Library in Simi Valley, California.
"Mrs. Reagan has been recovering slowly and has been adding a few appointments back on to her schedule, but was advised by her doctor today not to try and attend large events too far from home just yet," Joanne Drake, a spokeswoman for Reagan, said Tuesday.
"She personally invited Congressman Ryan and really wanted to be here, but sent her apologies to him earlier today."
Since President Ronald Reagan died in 2004 from Alzheimer's disease, the former first lady has been involved with the National Alzheimer's Association and its affiliate, the Ronald and Nancy Reagan Research Institute in Chicago.
However, she has been hospitalized at least twice in recent years and her public appearances have been rare. In February 2008, she spent two days in the hospital following a fall at her home, but the following month was able to hold a press conference endorsing Sen. John McCain for president outside her Bel Air, California, home.
Later that year, she was hospitalized in October for a broken pelvis a week after a fall at her home. She admitted herself to a hospital after experiencing "persistent pain," Drake said at the time, and tests revealed a fractured pelvis and sacrum, the triangular bone within the pelvis.
In 2009, Reagan helped unveil a statue of the late president in the Capitol rotunda, and in February 2011, she laid a wreath on his grave on what would have been his 100th birthday, during a reopening ceremony of his presidential library.
In August 2011, Reagan lost her balance and fell as she arrived at the presidential library to hear U.S. Sen. Marco Rubio, R-Florida, speak. Rubio caught her before she hit the ground, and she was escorted to her seat uninjured.
CNN's Gregg Canes and Stella Chan contributed to this report.