When is memory loss normal — and when is it a sign of something serious?

That question nags many seniors, including Shukla Biswas, 69, of Nashua, who recently retired after 45 years as a law librarian, then returned to work part-time.

“I’ve always had a computer memory,” said Biswas. “I could picture the book, see the pages turning and remember the lines on the page. Today I read a chapter in a pleasure book, then have to reread it the next day before going on to to the next. I’m forgetting a lot of stuff. It’s not like me at all.”

Bob Albom, 72, of Hooksett, worked over 50 years in hospitality management, and now teaches and makes presentations.

“I can have a thought in mind, then forget where I’m going with it,” Albom said. “My long-term memory is excellent. My short-term, not as much. People have been saying there’s so much on our minds it’s easy to forget. But I’ll start a sentence and all of a sudden forget where I was going with it.”

John Walker, 67, of Manchester said, “When you’re my age and can’t remember the name of a song, a favorite movie or a person I meet, is it because I’m busy and not focused — or is it a sign of something else?”

Worries about memory loss or worse, encroaching dementia are etched in the minds of many Granite State seniors — members of the state’s rapidly aging population, often described as a silver tsunami. Predictions for a steep uptick in diagnoses of Alzheimer’s disease and other forms of dementia make the collective anxiety intense.

Currently there are at least 24,000 cases of Alzheimer’s in New Hampshire, a number that is expected to increase by 33 percent by 2025, according to the Alzheimer’s Association’s state chapter. Nationally, one in six women and one in 10 men are expected to develop dementia.

In a 2016 statewide study, 8.9 percent of residents age 45 and older reported experiencing confusion or memory loss that’s happening more often or getting worse. Of those with memory problems, 42.8 said it has created functional difficulties, causing them to give up daily activities and/or interfering with work or social life.

Dr. Maureen O’Connor, a neurospychologist and associate director for education at Boston University’s Alzheimer’s Disease Center, co-author of ‘Seven Steps to Managing Your Memory: What’s Normal, What’s not, and What to Do about it,” said cognitive decline starts in one’s 20s and 30s and accelerates with aging.

Decreasing over time are processing speed, the ability to block out distractions, the ability to multi-task, and working memory, which includes mental manipulation such as being able to calculate how much change you’re due at the checkout.

“As we age, it becomes more difficult to learn as much new information. But the ability to retain it is relatively intact. People can experience some difficulty with information retrieval,” said O’Connor, who spoke last Wednesday at Birch Hill Continuing Care Retirement Community in Manchester. Remembering someone’s name when you recognize their face is a common complaint — even among actors, she said.

Relatively unaffected are our capacities to retain information and sustain attention, as well as procedural memories of how to do things such as play the piano or ride a bike. Semantic memory –- the memory of facts and words –- actually increases over our lifetime as we are exposed to new information and experiences.

Dementia may be an underlying issue when we have changes in memory and thinking that impact the way we function in daily life –- and others agree with that assessment.

“Someone else has to notice that your memory isn’t as good as it was, and you’re not able to do day-to-day things without help,” O’Connor said.

Often the hype surrounding memory decline can be worse than the reality -– and cause unfounded fears. Both depression and anxiety undermine memory, and can mimic memory decline.

O’Connor, who also works as a clinical neuropsychologist at the Bedford, MA Veterans Administration Hospital, said she’s seen patients as young as 45 who are panicked because of misplacing keys or forgetting the name of someone they know, which are not indicative of emerging dementia.

In Alzheimer’s Disease, which accounts for 40 to 70 percent of all dementias, “The hallmark feature is rapidly forgetting information: what you ate for breakfast, what someone told you moments ago. Distant memories remain preserved.” she said.

Vitamin B-12 deficiencies cause memory loss that resembles dementia, and chronic sleep disturbances such as insomnia and untreated sleep apnea also result in compromised cognition and memory decline. Both are reversible with treatment.

Silver Linings is a continuing Union Leader/Sunday News report focusing on the issues of New Hampshire’s aging population and seeking out solutions. Union Leader reporter Roberta Baker would like to hear from readers about issues related to aging. She can be reached at rbaker@unionleader.com or (603) 206-1514. See more at www.unionleader.com/aging. This series is funded through a grant from the Endowment for Health.