Physical Fitness Blunts the Impact of Depression on CVD Mortality
New study results should remind doctors to urge their patients to exercise at a time when just half of all Americans are doing the bare minimum.
Study after study has documented the compounding effects of depression on cardiovascular disease, but new research findings are offering some hope. In a recent retrospective study, individuals with higher levels of fitness were found to have a decreased risk of death due to cardiovascular disease later in life compared to those with lower fitness, even when they also had depression.
Among nearly 18,000 participants, those at a mean age of 50 with the highest fitness levels had a 61% lower risk of CVD death and a 16% lower risk of depression compared to their less-fit counterparts. The benefits extended into their late 60s and early 70s. Even among people subsequently diagnosed with depression, individuals with high fitness were 55% less likely to die due to CVD than those who got less exercise.
“What was surprising was that even in the face of a depressive episode which occurred later in life, the fitness that they had developed earlier in life had lowered their risk of cardiovascular disease,” lead author Benjamin Willis, MD, MPH (The Cooper Institute, Dallas, TX), told TCTMD. While no one debates the positive effects of exercise, these results were seen 20 to 24 years after their fitness was measured, Willis added. “It impressed us that fitness and physical activity could have such a long-range and long-lasting effect across the lifespan.”
The study was published online before print last week in JAMA Psychiatry.
Exercise is well-established as an important tool for preventing both depression and cardiovascular disease from developing in the first place, but also as one for mitigating both conditions after diagnosis. Given the complex interplay between the two diseases, the efficacy of exercise in preventing cardiovascular deaths among people also battling depression is unclear.
All participants were enrolled in the Cooper Center Longitudinal Study (CCLS), a long-running data set tracking lifestyle choices and fitness and their effect on other health outcomes over time. For the current analysis, the researchers looked at information on fitness, evaluated using treadmill testing, that was collected from 17,989 participants between 1971 and 2009, with a total Medicare follow-up of 117,218 person-years.
Individuals with scores in the lowest 20% were assigned to the “lower fitness” category, while those in the 60 to 100 percentiles were defined as “high fitness.” Information on depression diagnoses and cause of death were pulled from Medicare claims files between 1999 and 2009, with mortality information confirmed from National Death Index. Midlife fitness levels were then cross-referenced with subsequent depression diagnoses and death due to CVD.
After adjusting for sex, age, examination year, and various CV risk factors, among other things, Willis and colleagues found that high-fitness individuals had a significantly lower risk of developing depression than people with a lower fitness level (HR 0.84; 95% CI 0.74-0.95). In those without depression, a high fitness level was linked to less risk of dying from CVD (HR 0.39; 95% CI 0.31-0.48). And even among patients diagnosed with depression, those who were more fit in midlife had a lower risk of CVD death (HR 0.44; 95% CI 0.31-0.64).
The new data help to confirm associations that have been reported in the past, according to Heidi May, PhD (Intermountain Medical Center Heart Institute, Salt Lake City, UT), who commented on the study for TCTMD. “Exercise—no matter what other comorbidities that you have—was associated with an improvement or a decrease in risk in adverse outcomes,” she said. “Even though these patients were diagnosed with depression, if they exercised, their risk was still decreased.”
There are some limitations to this study, Willis noted, that could spur future research. Fitness was only measured once, when people were enrolled in the CCLS, though he pointed out that fitness levels in a population tend to remain consistent. Even if some patients did experience lifestyles changes due to unforeseen factors, it is unlikely that this would have a large impact, since the association between fitness and decreased CVD mortality was so strong, he added.
Most participants in this study were non-Hispanic white patients with access to healthcare, but Willis asserts these findings are still generalizable to the larger population.
“What we have seen and what other studies have shown is that the same risk factors that occur in [study participants] have basically the same impact on their outcomes—particularly cardiovascular outcomes—of the general population,” he said. “The risk factors tend to have the same effect, even though within this population we may not see the highest level of some of those risk factors that you might see in other populations.”
Additionally, the CCLS cohort skews male, with men making up 80.2% of the population analyzed for this study, which did not separate results by gender. Women have an increased risk of depression compared to men, May said, adding that this difference should be evaluated in future studies.
“I think, in general, you can generalize [this study] to females,” she said. “I do think it needs to be confirmed again and studied in a larger female cohort.” Willis noted that exploring how these risk factors affect women will be important research questions moving forward.
The most important takeaway from this study, Willis says, is the importance of exercise in one’s healthcare regimen. While physicians recommend exercise to their patients, only half of Americans get the minimum amount of exercise recommended by the Department of Health and Human Services, he said, and this study provides further evidence for fitness’ vital role in health aging.
“We would like to see more clinicians emphasize the role of physical activity and modifying their aerobic fitness early in life,” he said. “It’s never too late to start exercising, but the sooner the better.”
Willis B, Leonard D, Barlow C, et al. Association of midlife cardiorespiratory fitness with incident depression and cardiovascular death after depression in later life. JAMA Psychiatry. 2018;Epub ahead of print.
- Willis and May report no relevant conflicts of interest