Purpose in Life May Preserve Physical Function

Pam Harrison

August 16, 2017

A strong sense of purpose appears to help preserve physical function as individuals age, new research shows.

A longitudinal study led by Eric Kim, PhD, Harvard T. H. Chang School of Public Health, Boston, Massachusetts, found that "a sense of purpose in life, a modifiable factor, may play an important role in maintaining physical function among older adults."

The study was published online August 16 in JAMA Psychiatry.

Two Years Younger

"The vast majority of biomedical and public health research and care is focused on disease care and risk reduction, which is a very important approach, but we were motivated to do this study because focusing on resilience factors may be another way to help promote enhanced health and physical function into old age," Dr Kim told Medscape Medical News.

Data were derived from the Health and Retirement Study, a nationally representative study of adults older than 50 years living in the United States. The data were initially collected in 2006. Subsequently, surveys were conducted in this cohort every 2 years.

In each survey, researchers measured grip strength using a Smedley spring-type hand dynamometer. In addition, the participants' walking speed was measured as they walked 2.5 meters at their normal pace.

Cut points used to determine grip strength were 26 kg for men and 16 kg for women. The cut point used to assess walking speed was 0.8 m/sec. Weak grip strength and slow walking speed are indicators of increasing frailty, said Dr Kim.

For 4486 participants (mean age, 63 years), baseline hand grip scores indicated adequate physical function. For 1461 adults (mean age, 70.8 years), baseline walking scores indicated adequate physical function.

In 2006, purpose of life was determined by responses to the Purpose of Life subscale of the Ryff Psychological Well-Being scales. For this study, the Purpose of Life subscale was administered only once, in 2006.

After adjusting for sociodemographic factors, the investigators found that for each single standard deviation increase in purpose of life, as assessed on the Purpose of Life subscale, there was a 13% decrease in the risk of participants having a weaker grip strength 4 years later (P = .03 relative to baseline).

Similarly, in the same sociodemographic model, for each single standard deviation increase in purpose in life, there was a 14% decrease in the risk for slower walking speed at study endpoint (P < .001 relative to baseline).

Analysis of the same core model indicated that each single standard deviation increase in purpose was associated with a modest increase in walking speed over the study period, an effect size that the investigators characterize as roughly equivalent to being 2.5 years younger than participants' chronologic age.

A Piece of the Puzzle

Interestingly, the researchers found there was no association between baseline grip strength and walking speed and changes in life purpose 4 years later.

In the United States, almost 1 in 3 adults aged 65 years and older have difficulty walking three city blocks. Dr Kim said this finding is a wake-up call and suggests a need to boost efforts to maintain physical function in older adults.

"I think we need to have a 360-degree approach to helping older adults maintain physical function, because it's a key element to independent living and quality of life," Dr Kim said.

"Purpose in life may turn out to be one piece of the puzzle, although a robust and multilevel response is needed to help older adults maintain physical function," he added.

The investigators underscore that the reason purpose in life may preserve physical function is unclear, but one overarching mechanism is likely behavioral.

People with higher life purpose appear to be more proactive in taking care of their health. For example, they are more likely to avail themselves of preventive healthcare services, such as cancer screening, said Dr Kim.

"They may also have better impulse control and engage in better health behaviors overall," he added.

New Possibilities

In an accompanying editorial, Carol Ryff, PhD, University of Wisconsin, Madison, supports Dr Kim's suggestion that a strong sense of purpose may be a marker of good behavioral habits.

"One possibility is that older adults with higher levels of purposeful engagement are more physically active in their daily lives — they get up and do things every day," Dr Ryff writes.

She also points out that a growing number of studies show that psychological well-being can be modified by positive and negative changes in a person's environment. This finding points to new possibilities for improving health in later life, she notes.

"Leading a life of purpose not only feels good and meaningful, existentially speaking, it may also be an area of rich potential in which intervention studies and public health education programs might contribute to improved health of our ever-growing aged population," Dr Ryff concludes.

The study was funded by the National Institutes of Health. The authors and Dr Ryff have disclosed no relevant financial relationships.

JAMA Psychiatry. Published online August 16, 2017. Full text, Editorial

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