It may be compounded by physical decline such as loss of driving ability, decreased hearing or vision.
Retirement comes when that is no longer the case, when the physical decline is happening faster than any increase in experience is making up for.
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It says policies will be directed at reversing economic, social and physical decline in places where the private sector cannot step in without the government's help.
Researcher Dr Samuli Helle told the BBC News website it might be possible that the physiology underlying both reproductive and general physical decline was in some way linked.
It defines regeneration as reversing economic, social, environmental and physical decline in places where the market will not be able to achieve improvements without help from the government.
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In fact, Age UK goes as far as arguing it is just as important as the physical activity bit as loneliness is a risk factor for both cognitive and physical decline.
The new zones will be focused on areas of high growth potential, not just physical decline, and will be tailored to the individual needs of an area, it says.
Baseball players, race car drivers, skiers and lawyers all experience the same loss of a competitive edge when their physical functions decline to where they can no longer compete at the level necessary to compete and win at their peak.
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When I was growing up, the kind of people who today are lamenting the decline of physical books in the face of e-reading were busy bemoaning the decline of independent bookstores in the face of ruthless national chains.
Rather, HFCS supporters argue that obesity is as much a function of a corresponding decline in physical activity during the same period that HFCS consumption increased.
For publishers, digital-book revenue is still the fastest-growing segment of the business at a time when the sale of physical books is in decline.
The Internet era of music has forced established artists in particular to seek new revenue streams to compensate for the decline in physical album sales.
But a decline in physical sales, such as CDs, has led to earnings from live performance overtaking recorded music as a source of income for most musicians.
Researchers say the reason for the surge is partly because Americans are getting older and fatter, and possibly because of the country's decline in physical activity and some undefined changes in the American diet such as an increase in fat consumption.
While the reasons for the change at the top of the HFA were not disclosed, what is apparent is that licensing clearinghouses will certainly continue to face new challenges with the decline of physical media and the emergence of internet streaming.
The judge concluded that the media hordes and "looky loos" were a nuisance but caused only minor physical damage and a temporary decline in the house's value.
There had been a spate of rumours that Mr Sharon's unwonted quiescence attested to a decline of his physical prowess: aged 73, he was said to be vacant and forgetful.
This extraordinary artist, who made her feature debut 53 years ago in another movie with love in the title, "Hiroshima, Mon Amour, " is as unsparing as her director in depicting Anne's decline, though physical insults, and the erosion of identity, are only part of the story.
The study backs findings by other U.S. scientists, who warned that physical inactivity can hasten age-related decline.
With the proliferation of computer-based communication, one might have thought that the amount of physical paper sent through the postal service would decline, but it seems to have increased, at least from my perspective.
Reports Wednesday also said good Asian physical demand for gold has surfaced following the recent decline in prices.
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Reports this week say good Asian physical demand for gold has surfaced following the recent decline in prices.
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Traders also will keep monitoring reports about the voracious physical buying that was unleashed by a sharp price decline in mid-April.
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But the retailer, the largest U.S. bookstore chain by revenue, posted a 0.9% decline in comparable sales at its namesake physical stores in the quarter.
The researchers noted, however, that "the direction of causation is unclear, " meaning they couldn't tell if a healthier brain was a result of physical activity, or if people showing signs of cognitive decline weren't able to exercise.
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And people on probation must seek work but can decline job offers, such as those requiring hard physical labour in the sweltering midsummer.
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Returning to our current debacle, physical investment started a sustained and soon-to-be precipitous decline just before mid-year of 2007.
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