Objective neuropsychological test performance of professional divers reporting a subjective complaint of “forgetfulness or loss of concentration”

Abstract

Objective This study attempted to determine whether the higher prevalence of reported "forgetfulness or loss of concentration" among professional divers can be confirmed using objective neuropsychological tests. Secondary aims were to qualify the functional nature of the complaints and to ascertain whether reduced performance was linked to diving history. MethodsIn a case-control study, the neuropsychological test performance of divers complaining of moderate or severe "forgetfulness or loss of concentration" was compared with two age-matched control groups reporting no or slight "forgetfulness or loss of concentration" ("nonforgetful" divers and "nonforgetful" nondivers). The group differences were analyzed using a multivariate analysis of co-variance, followed by canonical discriminant function analysis. Altogether 102 divers with a complaint, 100 nonforgetful divers, and 100 nonforgetful nondivers completed the study. ResultsThe overall neuropsychological performance differed significantly between the groups [Pillai's trace: F(24,484)=2.04, P=0.003]. Verbal memory (Logical Memory and the California Verbal Learning Test), current intelligence (Wechsler Abbreviated Scale of Intelligence), and sustained attention (rapid visual processing) were poorer among the divers with a complaint than among the nonforgetful divers or the nonforgetful nondivers. The tests of memory, but not those of executive function, differentiated the divers with complaints from the two control groups. Mixed gas bounce diving and surface oxygen decompression diving, but not other techniques, were negatively associated with memory performance.Conclusions A cognitive complaint of divers was confirmed using objective tests of neuropsychological performance. Memory, rather than executive function, was affected at the group level, but only to a mild degree. The relationships between diving experience and neuropsychological test performance were small and only seen with diving techniques used in the offshore oil and gas industry.

Health status of professional divers and offshore oil industry workers

“…This supports the concept that the symptom is not entirely psychosomatic. Further, in a random sample selected from respondents from this study, we have found that the symptom was associated with poorer memory performance in objective neuropsychological testing [19] and reduced grey matter volume in brain areas associated with memory function in a preliminary magnetic resonance imaging analysis [20]. These differences, however, did not amount to abnormality.…”

Psychological and physical correlates of musculoskeletal symptoms in male professional divers and offshore workers

“…Neuropsychological testing methods have been described elsewhere [17] and are summarised here. The Logical Memory (LM) test, from the Wechsler Memory Scale III, and the California Verbal Learning Task (CVLT) II were used to measure immediate and delayed memory.…”

“…Current IQ measured using the Wechsler Abbreviated Scale of Intelligence (WASI) gave an estimate of global intellectual function (full score) and two sub-components of current intelligence: Matrix Reasoning (fluid intelligence) and Vocabulary (crystallized intelligence). The data gathered from this test battery were standardised ( z scores) and used to generate summary/composite scores reflecting memory performance (MemComp) and executive function (ExecComp) as described elsewhere [17]. Neuropsychological tests were always presented in the same order (CANTAB, CVLT, LM, WASI) using standardised instructions.…”

Neurological effects of deep diving

“…There is a real risk that the sample of respondents is not representative for British divers in general and that the impact on health related quality of life (HRQL) is underestimated [61,62]. Neuropsychological tests confirmed the cognitive complaints of the "forgetful" divers but other medical examinations were not included [63].…”