A limp handshake does not mean you are about to die

"Your Weak Handshakes Are Killing You"

Nope not true. As The New York Times explained, some journalists confused handgrip strength with handshake strength, and then mistakenly asserted that a weak handshake is an indicator of possible heart disease and early mortality:

"There was nothing wrong with the study that inspired these reports. Published last Wednesday in the journal The Lancet, it found that people with lower hand grip strengths had higher risks of suffering a heart attack or stroke and dying from cardiovascular disease.

But nowhere in the study did the authors mention anything about handshakes, and handshakes and grip strength are “completely different,” said Dr. Sripal Bangalore, an interventional cardiologist from NYU Langone Medical Center who was not involved in the study."

In the paper, the researchers examined ~140,000 subjects (aged 35-70) over a median period of 4 years. During that time 3379 (~2%) of the participants died. All of the participants had their handgrip strength measured (Figure 1). Researchers found that "grip strength was inversely associated with all-cause mortality (hazard ratio per 5 kg reduction in grip strength, HR=1.16), cardiovascular mortality (HR=1.17), non-cardiovascular mortality (HR=1.17), myocardial infarction (HR=1.07), and stroke (HR=1.09)." Amazingly, grip strength proved to be a better predictor of all-cause and cardiovascular mortality than systolic blood pressure. Thus, handgrip strength was significantly weaker for those more likely to die, revealing an inverse correlation between handgrip strength and mortality that was more informative than blood pressure.

This result is consistent with previous work. For example, I have posted on an earlier (smaller) study in which researchers examined whether performance on three physical tests could predict mortality. The three tests were handgrip strength, chair rise speed, and standing balance time. They observed the following:

"177 out of the 2766 participants (6.4%) died over the 13 year period. To emphasize, the bottom 20% performers on the physical tests had a mortality rate 3.68 times that of the top 20%. More strikingly, those who could not complete any of the three tests died at a rate 12 times larger than those would could complete the tests. This is no small effect."

The predictive power of the handgrip test alone appears to be roughly comparable to that of the combination of three tests. Perhaps the other two (chair rise time and standing balance time) are providing redundant information. On the other hand, one would expect the combination to provide a more complete picture of the person's health, and thus be a more accurate predictor, albeit only modestly.

Finally one should note that weak handgrip strength is not "causing" higher mortality. Rather, it is an indicator of potential health issues. Indeed, causation most likely works the other way around: cardiovascular dysfunction can directly or indirectly lead to weak handgrip strength.

More generally, your handgrip strength is a measure of your ability to perform strenuous exercise, and your ability to perform strenuous exercise depends on your cardiovascular health and overall fitness. A limp handshake, on the other hand, has nothing to do with your health, and thus cannot predict impending death; it is more representative of your mode of social interaction.

Figure 1. The dynamometer measures the strength of your handgrip in kilograms.