Reaction time as a predictor of mortality: the Radiation Effects Research Foundation Adult Health Study

Is simple reaction time or choice reaction time an indicator of all-cause mortality or CVD mortality?

OBJECTIVES

Simple reaction time (SRT) and choice reaction time (CRT) have been shown to be good indicators for quantitatively assessing the level of human cognitive impairment, but these parameters have also been linked to the risk of human death. This study aimed to quantitatively assess the independent predictive value of SRT or CRT for all-cause mortality or cardiovascular disease (CVD) mortality by conducting a meta-analysis of prospective studies.

STUDY DESIGN

The study design of this study is a prospective cohort study.

METHODS

We conducted a meta-analysis by combining hazard ratios (HRs) and 95% confidence intervals (95% CIs) of SRT or CRT with all-cause mortality or CVD mortality in healthy community residents aged 18 and over. Heterogeneity was evaluated by using Q statistics and Cochrane's I² statistics.

RESULTS

A total of seven prospective studies that examined all-cause mortality and CVD mortality were included. The pooled HR of all-cause mortality in SRT was 1.099 (1.065-1.134, I² = 11.9%), and an increased risk of CVD mortality was associated with lower SRT (HR = 1.186, 95% CI = 1.137-1.236; I² = 52.4%). Similarly, the pooled HR of all-cause mortality in CRT was 1.140 (95% CI = 1.085-1.197, I² = 33.7%). However, lower CRT was not statistically associated with an increased risk of CVD mortality.

CONCLUSION

SRT may be a predictor of all-cause-mortality and CVD mortality, and CRT is significantly associated with an increased risk of all-cause mortality.

Reaction times match IQ for major causes of mortality: Evidence from a population based prospective cohort study

Introduction

The association of premorbid cognitive ability with all-cause mortality is now well established. However, since all-cause mortality is relatively uninformative about aetiology, evidence has been sought, and is beginning to accumulate, for associations with specific causes of mortality. Likewise, the underlying causal pathways may be illuminated by considering associations with different measures of cognitive ability. For example, critics of IQ type measures point to possible cultural or social biases and there is, consequently, a need for more culturally neutral measures such as reaction times. We examine the associations of cognitive ability with major causes of mortality, including: cardiovascular disease, cancer and respiratory disease and compare the results for a standard IQ test, the Alice Heim 4 (AH4), with those for simple and four-choice reaction times.

Methods

Data were derived from the oldest cohort of the West of Scotland Twenty-07 Study. Participants were randomly sampled from the Central Clydeside Conurbation, a mainly urban area centred on Glasgow city. At baseline, aged 56, they were interviewed in their homes by trained interviewers; the AH4 was administered and reaction times measured using a portable electronic device. Vital status was ascertained via linkage to the NHS central register. Cox regression was used in SAS 9.4 for the main analyses. Adjustments were made for sex, smoking status and social class.

Results

Full data on AH4, RT and covariates were available for 1350 out of 1551. During 29 years of follow-up, there were 833 deaths: 279 cardiovascular disease (CVD) (168 CHD; 68 stroke); 291 cancer; 97 respiratory disease; 42 digestive disease; and 39 dementia. The 85 remaining deaths were a heterogeneous mixture with no cause accounting for more than 14.

AH4 scores were associated with most major causes. Digestive disease and dementia had similar effect sizes but were not significant. Within cardiovascular disease, there was an association with coronary heart disease but not stroke. The association with cancer was primarily due to those cancers related to smoking.

RT measures were mostly associated with the same causes of death. Where significant, effects were in the same directions and of similar magnitude. That is, lower AH4 scores, longer reaction times, and more variable reaction times were all associated with increased mortality risk from the major causes of death. A summary measure of RT outperformed the AH4 for most causes.

Conclusion

The association between intelligence with mortality from the major causes is also seen with reaction times. That effect sizes are of similar magnitude is suggestive of a common cause. It also implies that the association of cognitive ability with mortality is unlikely to be due to any social, cultural or educational biases that are sometimes ascribed to intelligence measures.

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Intelligence and reaction times are both associated with most major causes of mortality

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Effect sizes are of similar magnitude

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A summary RT measure provides the more parsimonious explanation for most causes

The Effect of Neurobehavioral Test Performance on the All-Cause Mortality among US Population

Evidence of the association between global cognitive function and mortality is much, but whether specific cognitive function is related to mortality is unclear. To address the paucity of knowledge on younger populations in the US, we analyzed the association between specific cognitive function and mortality in young and middle-aged adults. We analyzed data from 5,144 men and women between 20 and 59 years of age in the Third National Health and Nutrition Examination Survey (1988-94) with mortality follow-up evaluation through 2006. Cognitive function tests, including assessments of executive function/processing speed (symbol digit substitution) and learning recall/short-term memory (serial digit learning), were performed. All-cause mortality was the outcome of interest. After adjusting for multiple variables, total mortality was significantly higher in males with poorer executive function/processing speed (hazard ratio (HR) 2.02; 95% confidence interval 1.36 to 2.99) and poorer recall/short-term memory (HR 1.47; 95% confidence interval 1.02 to 2.12). After adjusting for multiple variables, the mortality risk did not significantly increase among the females in these two cognitive tests groups. In this sample of the US population, poorer executive function/processing speed and poorer learning recall/short-term memory were significantly associated with increased mortality rates, especially in males. This study highlights the notion that poorer specific cognitive function predicts all-cause mortality in young and middle-aged males.