A sudden change in routine that leads to being physically inactive for as little as two weeks may adversely affect the health of some people to a degree from which it is difficult to completely recover.
Those are the findings of a small study(academic.oup.com) published online last month in The Journals of Gerontology, Series A. The research showed that an abrupt drop in physical activity for a short time significantly increased glucose and insulin levels in older adults with prediabetes, and that many patients were unable to return to their previous state of health even after resuming normal activity.
"We expected to find that the study participants would become diabetic, but we were surprised to see that they didn't revert back to their healthier state when they returned to normal activity," said Chris McGlory, Ph.D., a Diabetes Canada Research Fellow in the Department of Kinesiology at McMaster University in Hamilton, Ontario, and the study's lead author, in a news release.(www.sciencedaily.com)
The CDC estimates that about 84 million American adults have prediabetes, but only 10 percent of people with the condition know they have it.(www.cdc.gov) Having prediabetes increases patients' risk for serious health problems, such as type 2 diabetes, heart disease and stroke. As such, the study findings could have significant implications for older adults who have or are at risk for developing prediabetes, as well as the family physicians who treat them.
- Recently published research suggests that a sudden drop in physical activity for a period as short as two weeks significantly increases glucose and insulin levels in older adults with prediabetes.
- In many study participants, these levels remained elevated even after resuming normal activity levels.
- Family physicians are encouraged to discuss physical activity levels with older patients, especially those who have recently experienced a prolonged illness or injury.
The researchers monitored the activity levels of 22 overweight adults ages 65 to 79 for five weeks. All of the study subjects met the American Diabetes Association's criteria(www.diabetes.org) for a diagnosis of prediabetes. Before enrollment, the participants were screened to ensure that they did not have diabetes, did not smoke and did not have any other chronic diseases.
In week one of the study period, the participants maintained their normal physical activity levels. For the next two weeks, participants were asked to reduce their activity to no more than 1,000 steps per day -- a decrease of about 70 percent in daily step count from baseline. Finally, the participants underwent a two-week recovery period during which they returned to previous activity levels.
Before participants entered the reduced activity period, the researchers obtained an oral glucose tolerance test, blood samples, a body composition assessment, a skeletal muscle biopsy and an isometric maximal voluntary contraction measurement for each participant. These tests were repeated in sequential order on the last two days of the reduced activity and recovery phases.
Although the researchers found no differences in body mass index, total body fat percentage, total lean mass and muscle strength during the study, they recorded several changes in the following areas:
- Glycemic control. Compared with baseline, the authors noted "significantly elevated" plasma glucose and insulin concentrations during the reduced activity phase. These concentrations remained elevated at recovery phase testing. Fasting plasma glucose and insulin concentrations also were elevated from baseline and did not return to previous levels at recovery phase testing.
- Muscle protein synthesis. Integrated muscle protein synthesis (MPS) rates were reduced from baseline at the end of the reduced activity phase and were not restored by the end of the recovery phase. Women had significantly higher integrated MPS rates than men across all study phases.
- Circulating inflammatory markers. Tumor necrosis factor-alpha, interleukin-6, and C-reactive protein concentrations all increased significantly between baseline and the reduced activity phase and remained elevated through the recovery phase.
"Our study represents a relevant clinical observation showing that prediabetic older persons are susceptible to inactivity-induced worsening of an insulin-resistant phenotype, as is observed in healthy older and younger persons," the authors wrote. "Uniquely, we show that the reversal of this phenotype, which occurs in younger adults, is impaired on return to normal activity in our population."
Context and Perspective
Several factors limited the applicability of the study's findings. These included:
- small sample size,
- lack of a comparator group of young patients,
- limited patient baseline data,
- use of laboratory test results as outcome measures rather than true patient-oriented outcomes, and
- short follow-up period to monitor patient recovery.
These shortcomings notwithstanding, the study's findings should give family physicians plenty to think about when considering patient care and the complex relationship between diabetes, age and physical activity.
According to the American Diabetes Association, more than 114 million Americans(www.diabetes.org) -- roughly 35 percent of the population -- have diabetes or prediabetes, meaning FPs are highly likely to see patients with one of these conditions.
Previous research, meanwhile, has shown that older adults who are recovering from a severe illness or surgery(www.ncbi.nlm.nih.gov) or are hospitalized for an extended length of time(www.ncbi.nlm.nih.gov) experience reduced ambulation and may take as few as 650 steps per day, meaning they could easily experience the same short-term physical inactivity as the study population and, thus, be at increased risk for diabetes.
So, what can family physicians do to help patients? According to Jennifer Frost, M.D., medical director for the AAFP's Health of the Public and Science Division, talking with patients about their activity levels is the key point to remember.
"This study highlights the importance of regular physical activity, particularly for our older patients," Frost told AAFP News. "When their activity level is affected by an illness or injury, we need to encourage return to activity as early as possible given the patient's circumstances."
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