Calling the age issue "a silly thing," Nancy Reagan continued her defense of President Reagan for the second straight day, saying she did not think the presidency has aged him as it did his predecessors.

"Everybody has said for the last 3 1/2 years that he has not aged," Mrs. Reagan said in Atlanta, where the media continued to test her reactions to the question of whether President Reagan, at 73, is too old to serve another four years. "As you look at pictures of other presidents they all aged and he has not."

Later, flying to Birmingham aboard Executive I for what the White House says is a "nonpolitical" swing on behalf of the fight against drug abuse -- even though the Reagan-Bush campaign is paying for it -- Mrs. Reagan said she thinks too much attention is being given to things that are "not important."

"The thing that is important is Mondale's positions and where he would like to lead the country, and my husband's positions and where he has led the country and where he would like to continue to lead the country."

It was a refrain repeated in San Antonio to reporters at the airport. "Mr. Mondale's position has always been taxes and spending," she said. "My husband is exactly opposite -- for economic growth that we have in the country and the good feeling."

As she made her way across the South in her three-day trip, she had a variety of well-known people greeting her. In Columbia, S.C., they were Jihan Sadat, there to address the University of South Carolina, and Nancy Thurmond, wife of Republican Sen. Strom Thurmond. In Birmingham, Alabama Gov. George Wallace's wife, Lisa, showed up at the airport to say goodbye, but told reporters she was not there as a representative of her husband. In San Antonio, Democratic Mayor Henry Cisneros welcomed her at the airport, "in my capacity as mayor," he said.

Though she does not like discussing issues with the media and has tried in the past to avoid such topics, she has been edged into the issues battle of the campaign. And she has shown that she can be a combative sparring partner with reporters.

Asked if the president has been put on the defensive by Mondale, Mrs. Reagan said, "Not at all, not at all. Mr. Mondale keeps saying things that are not so. Mr. Mondale keeps saying a lot of things that are not so."

She said her husband answered all of the questions in the Sunday night debate "completely and well," including those on abortion. "He did not segue into agriculture," she said, arching an eyebrow disapprovingly, without mentioning that Mondale had.

She said that "historically" the presidential debates haven't been important, and doubted that the vice presidential debate would be either.

When asked if she thought President Reagan had been fair to the American people and was told that many think he has hurt the elderly and those who are down and out, she bristled, "Now you're giving me the opposite line. No, I don't believe that at all."

She said bringing down inflation and providing more jobs is being fair to everybody -- "I mean, I don't know how you can interpret that as being unfair."

"I just ask the questions," the San Antonio reporter replied.

"Oh no," she laughed, "let's change places."

Earlier, when asked how much influence she has, she told an interviewer in Birmingham that "I don't think I exert any influence as far as policy goes, but I may have an influence as far as people are concerned. I'm more sensitive to people who might be helpful or not helpful" to the president.

"Maybe it's woman's intuition," she said on whether she is a better judge of people than the president is.

She said "Oh sure" that the candidacy of Geraldine Ferraro was a good idea and that it's "the natural evolution for women to become involved, just as I said it was time for a woman to be on the Supreme Court."

She was steering clear of any comments about Barbara Bush's recent sniping at Geraldine Ferarro. But she seemed undisturbed by it, saying, "It's like this age thing right now. It's when you get to this stage of the campaign, everybody gets a little off track."

When the president was preparing for the first debate, she said, "I sat in -- not really sat in -- I was there when they came up to Camp David and sort of in and out."

But she shook her head when asked if she would be involved in rehearsals for the next debate. She said the president was "his own best judge, he always has been" about such tactics as incorporating statistics into his arguments. She said they did talk about his performance after the debate.

"He was annoyed that when he would say something, make a statement of policy or position, and it was as if he had talked to the wall, because Mondale would come back and say President Reagan is going to do thus and so, as if he had never said he was not going to do thus and so." She said she thought 90 minutes is a long time for a debate -- "I'm not thinking in terms of the participants, but of the audience. I think it's a long time for an audiences' attention span."

Age is something she and the President "never think about" she said in an interview aboard her Air Force C-9 jet. "It is really all in your mind how old you are. If you dwell on how old you are, then you're going to be old. I think you can psyche yourself into getting old. I've known people who are old at 40 and I've known people who are young at 90. Age never enters my mind," she said.

She said she believes it's important to "be involved -- that's why retirement is so bad. You haven't got anything to think about but yourself. The minute you start to do that, you're dead."

This morning, at Atlanta's Northside High School, five students inteviewed Mrs. Reagan about her campaign against drug and alcohol abuse. Questions were approved by the White House several days in advance according to one panelist, William Neal. He said he and his colleagues, chosen by a faculty member, developed 40 questions of which 30 were sent to the White House and 19 were returned as acceptable.

"The 11 I wanted to ask were more pointed," Neal said. He added that the group stayed away from "political stuff," because they decided the focus should be on drugs.

With several hundred students looking on, Mrs. Reagan's response to one question about what she would tell a teen-ager who arrived at a party where drugs were being used, was "I would say I want to go home . . . if that wasn't possible I would call my parents to come and get me. I know that's hard to do, but you've got to do it."

At another point, continuing the message that has become a part of her presentation, she said she would tell a child that "we only make this trip once and we should really use it . . . So much is waiting out there and they need you, but clear eyed."

The apple pie was missing but she dispensed ample portions of motherhood by reminding her audience that she was visiting them both as first lady and as a mother.

"I know there is no hurt like the one a child can give you, and when a child gets into drugs, it is a very frightening and terrible thing to see," she said speaking as a mother.

As first lady, she said her position provided her with a "platform," to get her message across.

Asked if she sees herself as a mother figure, she said she just says what she feels and that "maybe as you do more of it, it becomes easier." And on whether she thinks the president is a father figure, she said she didn't know. "But he's a very hard man to dislike."