The world is growing older.  Except for Africa south of the Sahara, the average age is increasing.

There are more old people thanks to medical advances that, together with lifestyle changes, help prolong life.  At the same time, there are fewer young people as parents choose to have smaller families.  While China ended its rule requiring one-child families, many Chinese seem to have grown accustomed to it.

The increase in the length of life is not consistent around the world or even in the U.S.  There is a 15-year difference in life expectancy between the wealthiest and poorest Americans, according to a report in London’s Financial Times.

There’s also a difference between people who keep employed, even in volunteer jobs or athletic activities, and those who become couch potatoes in retirement.  Keep active and you live longer and healthier.

One major factor in extending lives is a reduction in the number of smokers.  Smoking’s toll shows up as people age.

Obesity is the new smoking.  About one-third of Americans is obese and another third is overweight. This causes high health care costs and a lower American lifespan than in Japan, France, and Greece, among many others.  The median age in the U.S. is 38.  In Japan, it is 47.3 and, in Greece, 44.5.

Maine, at 44.6, has the highest median age of any state.  That makes the state a world leader.  What it learns about dealing with aging and improving the quality of life for older people could provide valuable tools for the rest of the country and even other countries.  Here’s an economic development opportunity.

Longer lives are also having political effects.  A higher percentage of older people vote than do other age groups.  Traditionally mostly Republicans, they have begun to move toward the Democrats.  In political campaigns, older Americans should be added to the list of target groups like women, minorities and the young.

The most obvious effect of an older population is among the presidential candidates.  Bernie Sanders, 77, and Joe Biden, 76, lead the Democratic pack.  Donald Trump, 72, is the oldest person ever elected president.  Elizabeth Warren, 69, could end her first term at 75, older than Trump will end his.

Robert Kaiser, 76, a former editor of the Washington Post, worries about older presidents.  He writes the presidency is “perhaps the hardest job in the world.”  Aging experts think it is a job for a person of 50 more so than one of 70, he says.

Because individuals differ from one another, general findings may not apply to every older person.  But studies show that, on almost all measures of intellectual ability, old people suffer in comparison with younger adults.

It may be difficult for older people to admit the reduction in their memory or ability to handle complex tasks.  You can more easily recognize reduced lung capacity or muscle strength.  For older people, including presidential candidates, mental capacity slows down like physical ability.

Ronald Reagan is currently ranked as the oldest president, though Trump would pass him.  His deteriorating mental agility while in office was recognized.  That can be a factor for today’s candidates.  Plus, older presidents have a significantly greater possibility of dying in office than usual.

Presidential candidates make only one decision during the course of a campaign that will bind them if they gain the highest office.  And it is a decision they usually make in the euphoria of their victory just before or just after they have received their party’s nomination.

The nominees pick their vice presidential running mates for a variety of reasons.  A man has picked a woman.  A black has picked a white.  A northerner has picked a southerner.  A Republican has picked a Democrat.  These moves were designed to “balance” the ticket and improve chances of winning.  All, except one, worked.

But the principal role of the vice president is to be a “heartbeat away” from being president.  In 1944, Democrat kingmakers were reasonably sure that Franklin D. Roosevelt would not live through his fourth term and selected Harry Truman, a man who knew his way around Washington, to succeed him.

Given the age of some of the presidential candidates, they should recognize voters are electing two people who could be president, not just a candidate and a ticket balancer.  Of course, if older candidates make a choice, others will have to follow.  The wisdom of their choices can then be a factor in our choice.

Then, the rest of us can focus on taking off a few pounds and keeping active.