Friday September 10 2010
The study looked at grip strength, not handshakes
“A strong handshake will help you hold on to life,” the Daily Mail reported today. The newspaper also said that good balance, a brisk walking pace and the ability to get up from a chair easily are all potential signs of a longer life.
These results come from a good-quality review of the evidence on the association between measures of physical capability, grip strength and balance, and the risk of an earlier death. The review found evidence that better performance in these measures was linked to longer life expectancy in older adults (mainly those aged over 60), a result that is likely to be reliable.
It remains to be seen whether this link also applies to younger adults and whether interventions to improve these aspects of physical ability can help reduce the risk of earlier death. It should be noted that the study measured grip strength rather than handshakes. For obvious reasons, it’s probably best not to grip someone with all your strength when shaking hands.
Where did the story come from?
The study was carried out by researchers from University College London and was funded by the UK Medical Research Council’s Population Health Sciences Research Network. The study was published in the peer-reviewed British Medical Journal.
The Mail, Guardian and Independent all covered this story in a balanced way. The Mail suggested that the link with grip strength was found “even in the young”. Although a small number of the studies reviewed assessed grip strength in people with an average age under 60, the exact average age in these studies was not clear.
While several newspapers suggested that a person’s handshake can predict their risk of death, having a firm handshake is not necessarily the same as having a strong maximum grip strength, and the link between the two is tenuous.
What kind of research was this?
This systematic review identified and summarised the existing research on whether there is an association between different objective measures of physical capability and risk of death. The review also carried out a meta-analysis (statistical pooling) of the results of similar studies to obtain an overall assessment of the strength of any links.
The researchers say that a growing body of evidence suggests that there is a link between objective measures of capability, such as grip strength or standing balance, and risk of death. They say that these measures could potentially be used as simple screening tools to identify people who may benefit from activities such as strength or balance training. Alternatively, they say the tools could be used to assess the effectiveness of these types of training programmes.
There have been no previous systematic literature reviews of some of these measures, such as standing balance, although the link with grip strength has been systematically reviewed. However, a meta-analysis of the studies identified had not yet been performed.
A systematic review is the best way to summarise all the best-quality studies on a particular question, and to give an overall picture of what the existing evidence indicates.
What did the research involve?
The reviewers searched research databases for relevant studies that had been published before May 2009. They also looked at the studies’ references to find other relevant studies. Where possible, they contacted the studies’ authors to identify relevant unpublished research. They included observational studies that looked at whether there was a link between a measure of physical capability and risk of death in people of any age living in the community (i.e. not in facilities such as nursing homes).
The researchers did not include studies on groups of patients with specific conditions. The measures of physical capability that the researchers were interested in were grip strength, walking speed, the time it took to get out of a chair and the ability to balance standing on one foot. They asked the authors of the research studies to provide them with analyses looking at the link between each measure of physical capability and time to death due to any cause. They asked the authors to take age, gender and body mass index into account in their analyses as these factors might affect results. The researchers used the results from published analyses where the authors could not provide these analyses.
They aimed to compare people in the top 25% of each physical capability measure with those in the lowest 25%. The main outcome of interest was death from any cause.
Results from the studies were then pooled using standard statistical methods. The researchers also used standard statistical methods to assess whether the studies had similar enough results, which would suggest whether they were appropriate for pooling together.
What were the basic results?
The researchers’ initial search identified 33 sets of results which met their inclusion criteria. These included 16 sets of results from published studies and 17 special analyses produced to the researchers’ specifications by the original study authors. Most of the studies providing these results were considered to be of good quality, in part because capability was often measured by trained professionals and deaths were identified using reliable methods.
All of the studies of walking speed, chair rising and standing balance were in older populations, with an average age of over 61. Some of the studies of grip strength were in younger populations, with five studies in people with an average age of less than 60 years.
The researchers could not carry out a statistical pooling of the results of the five studies of standing balance (featuring 16,266 people in total) as the studies did not carry out their measurements and comparisons in the same way. All of the studies identified showed some evidence that poorer standing balance was associated with greater risk of death during follow-up, but these associations were not all large enough to be statistically significant.
In their meta-analyses, the researchers pooled the results of:
- 14 studies of grip strength, featuring 53,476 people
- five studies of walking speed, featuring 14,692 people
- five studies of chair rise time, featuring 28,036 people
This pooling took into account age, gender and body size, which could affect results, and found that:
- Those with the lowest grip strength had a 67% greater risk of death during the follow-up period than those with the strongest grip strength (hazard ratio [HR] 1.67, 95% confidence interval [CI] 1.45 to 1.93).
- Those who were slowest to get out of a chair had a 96% greater risk of death during follow-up than those who were fastest (HR 1.96, 95% CI 1.56 to 2.45).
- Those with the slowest walking speed had 2.87 times the risk of death during follow-up than those with the fastest walking speed (HR 2.87, 95% CI 2.22 to 3.72).
- In some of the analyses, the studies had varying results, which may be because they included different populations or had other methodological differences. Taking out individual studies from these analyses did not change the results, and none of the factors that were assessed (age of participants, length of follow-up, country where the study was performed or gender) could fully explain these variations in results.
How did the researchers interpret the results?
The researchers concluded that objective measures of physical capability can predict the risk of death from any cause in older people living in the community. They suggest that these measures may be useful in identifying older people who are at greater risk of death.
This well-conducted research found links between various objective measures of physical capability and risk of death, and its results are likely to be reliable. There are a few points to note:
- As the studies were observational, the observed link with mortality may have been caused by factors other than physical capability that may have differed between the groups compared. However, physical capability was used as an indicator of risk of death rather than being suggested as the cause of the change in risk, so this is perhaps of less concern.
- The measures were mainly assessed in older people and, therefore, the results may not apply to younger populations. In fact, some exploratory analyses suggested that the link between grip strength and risk of death was weaker in studies where participants had an average age of less than 60 years at the start of the study.
- It is not clear whether these measures of physical capability would be better or worse predictors of risk of death than other measures of health.
- The study looked at all deaths, regardless of cause, and did not identify specific causes of death that may be linked to physical capability. Looking at whether these physical capability measures are linked to specific causes of death might provide clues as to the causes of the link.
Further research is needed to determine whether specific interventions, such as those designed to improve physical capability, could help reduce the risk of death in people identified as being at greater risk according to these measures. The researchers say that a person’s level of physical functioning in later life reflects their peak achieved during earlier growth and development, as well as the rate of decline.
Ideally, further research should look at how early growth and development determine physical capability in older age.