The work, based on four years of stroke care data gathered in Ontario, shows that more than one in three people who experience a stroke don't arrive at the hospital by ambulance.
Calling 911 is the appropriate response to signs or symptoms of strokes, experts say.
"Call an ambulance," said Patrice Lindsay, director of performance and standards for the Canadian Stroke Network, and a stroke survivor.
"When you start having a stroke, you can get very sick very quickly," she said. "By calling an ambulance, you get faster service in the right place."
That's because the goal isn't just to get to a hospital, it's to get to a hospital that can treat a stroke patient.
Showing up at a small hospital without a CT scanner — a piece of imaging equipment that is critical for stroke diagnosis and care — means the patient will need to be transferred or redirected to a facility that can handle acute stroke cases. And that means added delay, Lindsay said.
Ambulance staff are trained to assess patients for the telltale signs of stroke. If they see signs like drooping muscles on one side of the face, or weakness on one side of the body, they will "scoop and run," she said.
Lindsay says ambulances will also call ahead so the receiving hospital can arrange to free up a CT scanner and have a stroke team on hand when the patient arrives.
The aim is to diagnose and start treatment for the stroke within a critical window of time — 4.5 hours. Within that time frame, doctors can give clot-busting drugs that can significantly lessen the damage of a stroke.
The medical community uses the adage "time is brain" — referring to the fact that clot-busters administered within those first few hours can significantly reduce the volume of brain that sustains damage, thereby reducing the risk of permanent disability.
"So the message we have to get out is a) recognize the symptoms and b) don't take that chance. Because it could be the difference between walking out of the hospital of your own accord in a week or two versus ending up in permanent long-term care," Lindsay said.
Lindsay had a stroke at age 38. The sudden onset of weakness on the left side of her body tumbled her to the floor. She remembers picking up her useless arm with the unaffected one, but having no sensation in it. "I didn't know I had a left side of my body."
She did not receive care in time to get those critical drugs. "I was one of the non-ideal cases," she said, admitting she attacks with a passion her job of assessing how well the system is doing at treating strokes.
The study, released by the Canadian Institutes for Health Information, looked at treatment of more than 62,000 stroke patients in Ontario from 2006-2007 through 2009-2010.
Kathleen Morris, CIHI's director for health system analysis & emerging issues, says much has improved in terms of stroke treatment in recent years, but there is room for improvement. And she agreed that people experiencing the symptoms of stroke shouldn't wait to see if the symptoms will pass.
"It might be nothing if you had a sudden severe headache and some dizziness," said Morris. "And the worst case from that is you would have to sit in the emergency department for a few hours and possibly feel slightly embarrassed.
"(But) how much of a gamble are you prepared to make that it's not a stroke? You might be wrong, but missing the stroke means you've missed the window where you can get treatment and you may have something that is debilitating for the rest of your life."
Symptoms of stroke include sudden weakness or loss of sensation in the face, arm or leg; difficulty speaking or understanding speech; sudden trouble with vision; sudden severe headache and dizziness or a sudden loss of balance.