News · Sleep
Weak grip and low weight tracked with insomnia after 60
A SLEEP study of 5,824 older adults found low muscle strength and being underweight each tracked with insomnia, and together more than doubled the odds.
Based on a peer-reviewed cross-sectional study in SLEEP
- A territory-wide study of 5,824 adults aged 60 and over, 77.8% of them women, published in SLEEP.
- 696 participants, or 12.0%, met the threshold for insomnia on the Insomnia Severity Index.
- Low muscle strength, measured by handgrip, tracked with higher odds of insomnia even after adjusting for depressive symptoms.
- The pattern was graded: odds rose steadily from the strongest quarter of the sample to the weakest, reaching 1.56 times.
- Among body weight categories, only underweight tracked with insomnia. Overweight and obesity did not.
- Low strength plus underweight together carried the highest odds, at 2.27 times the reference group.
- The largest absolute differences in predicted insomnia ran from 6.3% to 10.6%.
- This is cross-sectional: strength, weight and sleep were all measured at the same moment, so nothing here shows which came first.
Sleep research on body weight has mostly looked at the heavy end, where sleep apnea lives. A study in SLEEP looked at the other end instead, and found the thin, weak end of the distribution was where insomnia clustered.
Underweight and low muscle strength were independently associated with insomnia, with their co-occurrence showing highest prevalence of insomnia.
Two measures nobody usually combines
Handgrip strength and body weight are both routine, both cheap, and until now both studied apart. This territory-wide study examined joint associations of muscle strength and body weight status with late-life insomnia, which is the part that had not been done.
Doing it jointly matters because the two travel together. Someone underweight in their seventies is often also losing muscle, and separating those two is the only way to know which one the sleep problem tracks with.
How 5,824 older adults were assessed
Insomnia was identified using the Insomnia Severity Index, a standard questionnaire rather than a sleep laboratory.
Muscle strength was measured using handgrip strength, and body weight status was assessed via body mass index, waist circumference, and body fat percentage, so the weight picture does not rest on a single crude number.
Among 5,824 older adults aged 60 years and above, 696 participants, or 12.0%, had insomnia. Just over three-quarters of the sample were women.
The strength gradient
Weak grip tracked with insomnia, and it did so in steps rather than as a threshold. Clinically defined low muscle strength was associated with significantly higher odds of insomnia, holding up after adjustment for depressive symptoms.
The gradient is the more persuasive part. Odds rose progressively from highest to lowest strength, reaching 1.56 times in the weakest group.
Adjusting for depression matters here. Low mood drives insomnia and also drives inactivity, so a result that survives that adjustment is harder to dismiss.
Where the weight finding goes against expectation
The body weight result runs opposite to the usual sleep story. Compared with normal weight, only underweight was associated with higher odds of insomnia, while overweight or obesity did not carry the same association.
Combining the two produced the largest effect. Low muscle strength was associated with higher odds of insomnia in normal weight and underweight groups, reaching 2.27 times in those who were both underweight and weak.
In absolute terms the paper reports differences in predicted insomnia probability from 6.3% to 10.6%, which keeps the finding in proportion.
What a single snapshot cannot show
Everything was measured at the same moment. Strength, weight and sleep were captured together, so the direction is undetermined: weak muscles may disturb sleep, poor sleep may waste muscle, or a shared underlying illness may produce both.
The sample also skews heavily female at 77.8%, so estimates for men rest on far fewer people.
What the study does establish is a group worth asking about. Older adults who are thin and weak have been largely absent from a sleep literature preoccupied with the opposite body type, and they turn out to have more insomnia, not less.
People also ask
Would getting stronger improve my sleep?
This study cannot say, because everything was measured at once. Strength training might improve sleep, poor sleep might erode strength, or a third factor such as underlying illness might drive both. Resistance training has plenty of other evidence behind it in older adults, so it is a reasonable thing to do regardless. Just not on the strength of this finding.
Why does being underweight matter more than being overweight?
That is the surprise in the paper, since sleep research usually focuses on the heavier end through sleep apnea. Here, compared with normal weight, only underweight was associated with higher odds of insomnia, while overweight and obesity were not. The authors frame it as an underweight spectrum, pointing at frailty and low reserve rather than at airway obstruction.
How is insomnia defined here?
By the Insomnia Severity Index, a standard questionnaire covering difficulty falling asleep, staying asleep, waking too early, and how much that bothers a person during the day. Twelve percent of this sample met the threshold, which is in the usual range for this age group.
How big is the combined effect?
In relative terms, low strength with underweight carried 2.27 times the odds of the strongest, normal-weight reference group. In absolute terms the paper reports differences in predicted insomnia probability of 6.3% to 10.6%, which is the more useful figure: a difference of several percentage points, not a transformation.
Does the sample limit what this shows?
Somewhat. It is a territory-wide sample of adults 60 and over, but 77.8% are women, so the male estimates rest on far fewer people. And a cross-sectional design captures a single moment, which is a particular problem when both strength and weight change over years.