Tremor severity and age: a cross-sectional, population-based study of 2,524 young and midlife normal adults

The effect of socially evaluated multitasking stress on typing rhythms

Individuals have unique typing rhythms characterized by specific keystroke dynamics. Changes in state and cardiovascular responding are well documented manifestations of the fight-flight response to stress. However, as stress also leads to changes in muscle tone and motor control, typing rhythms may also be impacted. We aim to determine which individuals are experiencing stress through their typing rhythms and identify universal keystroke markers of stress. Participants (N = 116) typed 80 repetitions of a 6-word, 30-character phrase before and after 15 min of critically evaluated multitasking stress. Cardiovascular, hemodynamic, and state variables were compared across baseline, stress, and recovery periods and measures of typing rhythm were derived for each period and classified using machine-learning algorithms. Critically evaluated multitasking led to significant changes in all stress measures, demonstrating highly robust stress reactivity. Machine learning algorithms accurately classified stressed typing for each individual based on their typing rhythms; however, no universal keystroke markers of stress were identified. Using typing rhythms. We were able to determine whether an individual was stressed or not, but the markers used for classification differed between individuals. These individual changes may provide opportunities for identifying stressful periods through keystroke monitoring, as well as the potential for early identification of disorders which may impact fine motor control. Typing rhythms could therefore be used to monitor health and well-being in individuals who use keyboards in various situations. This is the first rigorous assessment of stress and typing rhythms and has led to the development of a feasible and highly reproducible research protocol.

Is essential tremor a family of diseases or a syndrome? A family of diseases

It is now well-established that essential tremor (ET) can manifest with different clinical presentations and progressions (i.e., upper limb tremor, head tremor, voice tremor, lower limb tremor, task- or position-specific tremor, or a combination of those). Common traits and overlaps are identifiable across these different subtypes of ET, including a slow rate of progression, a response to alcohol and a positive family history. At the same time, each of these manifestations are associated with specific demographic, clinical and treatment-response characteristics suggesting a family of diseases rather than a spectrum of a syndrome. Here we summarize the most important clinical, demographic, neuropathological and imagingfeatures of ET and of its subtypes to support ET as a family of identifiable conditions. This classification has relevance for counseling of patients with regard to disease progression and treatment response, as well as for the design of therapeutic clinical trials.

The spiral axis: A comparison of unaffected first-degree relatives of essential tremor cases vs. controls

We previously observed that during a spiral drawing task, in essential tremor (ET) cases, the tremor wave forms align along a single predominant axis. This interesting clinical feature can distinguish ET from dystonia cases. We now investigate whether the unaffected relatives of ET cases also express this trait, albeit perhaps in a milder form. To address our aim, we assessed the spiral axis in 237 unaffected first-degree relatives of ET cases (FD-ET), comparing them to 105 controls (Co). A movement disorder neurologist assessed four hand drawn spirals for the presence of a single identifiable tremor orientation axis. A spiral axis score (range = 0-4 [a single axis on 4 spirals]) was assigned to each enrollee. FD-ET had higher spiral axis scores than Co. In a contingency table, the distribution of spiral axis scores differed in the two groups: FD-ET (highest) and Co (lowest) (ordinal chi-square test p = 0.014). Furthermore, when spiral axis scores were examined as a continuous measure, the groups differed (Mann-Whitney test p = 0.03) - with the means being 0.51 (FD-ET) and 0.26 (Co). These data have scientific implications. They (1) show that such axes are more common in relatives of ET cases than controls, and (2) raise the possibility that the spiral axis may be an early subclinical feature of ET.

Tremor in normal adults: A population-based study of 1158 adults in the Faroe Islands

There are virtually no population-based data on tremor in normal individuals. Using a population-based sample of 1158 normal adults ages 40-98 years in the Faroe Islands, we characterized the extent of normal action tremor across age and gender strata. Participants drew two Archimedes spirals with each hand, and tremor was systematically quantified by a senior movement disorder neurologist using a reliable and valid ordinal rating scale (ratings = 0-3). Tremor was nearly universal - 1145 (98.9%) participants had a total mean spiral score > 0. Older age was associated with more tremor (p < .001) and spiral scores were higher in males than females (p < .001). The proportion of individuals with a spiral rating ≥ 1.5 (i.e., more than mild tremor) was low (1.8% - 8.5%); however, this value reached 19.6% in left-hand spirals of males ≥70 years old. In this population-based study of more than one thousand normal adults, the vast bulk (i.e., 98.9%) had tremor on spiral drawing. In general, the tremor was mild. The proportion of individuals with tremor above the mild range varied across age and gender strata. These extensive data may be used as a gold standard for defining normal levels of tremor within adult populations.

Prevalence of Essential Tremor in the Faroe Islands: A Population-Based Study

BACKGROUND

No studies of the prevalence of one of the most common movement disorders, essential tremor (ET), have been undertaken in the Faroe Islands. Given the potential for founder effects in the Islands, and the highly genetic nature of ET, the Faroe Islands provide a particularly interesting setting in which to study the prevalence of ET.

OBJECTIVE

To estimate the prevalence of ET and study its characteristics.

METHODS

We used a 2-phase, population-based design, screening 1,328 randomly selected Faroese individuals aged ≥40 years. A subsample of 282 individuals who had returned the spirals and questionnaire was selected to participate in an in-person clinical evaluation. Tremor was systematically quantified by a senior movement disorder neurologist with particular specialization in tremor using a reliable and valid clinical rating scale followed by the application of rigorous diagnostic criteria used by tremor investigators internationally.

RESULTS

The overall crude prevalence was 2.9%. The age-adjusted prevalence was 3.1%. There was an age-associated rise in prevalence; by age ≥70, prevalence reached 4.8%. Twenty six of 27 (96.2%) were previously undiagnosed.

CONCLUSIONS

This is the first population-based study of the prevalence of ET in the Faroe Islands. The estimated prevalence was similar to studies using the same or comparable methodologies.

Older age relates to worsening of fine motor skills: a population-based study of middle-aged and elderly persons

INTRODUCTION

In a population-based study of 1,912 community-dwelling persons of 45 years and older, we investigated the relation between age and fine motor skills using the Archimedes spiral-drawing test. Also, we studied the effect of brain volume on fine motor skills.

METHODS

Participants were required to trace a template of a spiral on an electronic drawing board. Clinical scores from this test were obtained by visual assessment of the drawings. Quantitative measures were objectively determined from the recorded data of the drawings. As tremor is known to occur increasingly with advancing age, we also rated drawings to assess presence of tremor.

RESULTS

We found presence of a tremor in 1.3% of the drawings. In the group without tremor, we found that older age was related to worse fine motor skills. Additionally, participants over the age of 75 showed increasing deviations from the template when drawing the spiral. Larger cerebral volume and smaller white matter lesion volume were related to better spiral-drawing performance, whereas cerebellar volume was not related to spiral-drawing performance.

CONCLUSION

Older age is related to worse fine motor skills, which can be captured by clinical scoring or quantitative measures of the Archimedes spiral-drawing test. Persons with a tremor performed worse on almost all measures of the spiral-drawing test. Furthermore, larger cerebral volume is related to better fine motor skills.

Tremor in school-aged children: a cross-sectional study of tremor in 819 boys and girls in Burgos, Spain

BACKGROUND

Mild hand tremor occurs in most normal adults. There are no surveys of the prevalence or clinical correlates of such tremor among children.

METHODS

A cross-sectional study of tics, tremor and other neurological disorders was conducted in Spanish children; thus, 819 schoolchildren in Burgos, Spain, drew Archimedes spirals with each hand. Tremor in spirals was rated (0-2) by a blinded neurologist and an overall tremor rating (0-4) was assigned.

RESULTS

The mean age was 10.9 ± 3.1 years. A tremor rating of 1 (mild tremor) was present in either hand in 424 (51.7%) children, and in both hands in 88 (10.7%) children. Higher tremor ratings were very uncommon. The overall tremor rating was higher in boys than girls (1.31 ± 0.41 vs. 1.22 ± 0.34, p = 0.002) and correlated weakly yet significantly with age (ρ = 0.09, p = 0.01). Within subjects, the left hand spiral rating was greater than the right (p < 0.001).

CONCLUSIONS

In this cross-sectional study of 819 Spanish schoolchildren, mild tremor was commonly observed. As in adults, males had more tremor than females, tremor scores increased with age, and tremor scores were higher in the left than right arm, demonstrating that these clinical correlations seem to be more broadly generalizable to children. The functional significance of tremor in children, particularly as it relates to handwriting proficiency, deserves additional scrutiny.