Hans Chr. Petersen

Predictors of mortality in 2,249 nonagenarians--the Danish 1905-Cohort Survey.

Objectives: To elucidate whether well‐known predictions of mortality are reduced or even reversed, or whether mortality is a stochastic process in the oldest old.

Cognitive Impairment and Mortality among Nonagenarians: The Danish 1905 Cohort Survey

Cognitive impairment has been associated with increased mortality. Most studies, however, have only included small numbers, if at all, of the very old. In a large nationwide survey of all Danes born in 1905 and still alive in 1998, where the baseline examination was conducted, we examined the impact of cognitive impairment on mortality over a 2-year period. No cognitive impairment was defined as a score of 24–30 points on the Mini Mental State Examination, mild cognitive impairment was defined as a score of 18–23 points, and severe impairment was defined as a score of 0–17 points. Cox regression analysis was applied to adjust for a number of known and suspected factors known or suspected of being associated with cognition and mortality (e.g. sociodemographic factors, sex, smoking, alcohol consumption, depressive symptoms, and physical abilities), and yielded hazard ratios (95% confidence interval) of 1.24 (1.00–1.55) for mildly impaired and 1.73 (1.37–2.20) for severely impaired Danes compared to individuals with no impairment. Cognitive impairment predicts mortality among the very old, even after controlling for most known predictors of mortality.

CHANGES IN CLICK SOURCE LEVELS WITH DISTANCE TO TARGETS: STUDIES OF FREE-RANGING WHITE-BEAKED DOLPHINS LAGENORHYNCHUS ALBIROSTRIS AND CAPTIVE HARBOUR PORPOISES PHOCOENA PHOCOENA

ABSTRACT Probably all odontocetes use echolocation for spatial orientation and detection of prey. We used a four hydrophone “Y” array to record the high frequency clicks from free-ranging White-beaked Dolphins Lagenorhynchus albirostris and captive Harbour Porpoises Phocoena phocoena. From the recordings we calculated distances to the animals and source levels of the clicks. The recordings from White-beaked Dolphins were made in Iceland and those from Harbour Porpoises at Fjord & Baelt, Kerteminde, Denmark during prey capture. We used stringent criteria to determine which clicks could be defined as being on the acoustic axis. Two dolphin and nine porpoise click series could be used to track individual animals, which presumably focused on the array hydrophones or a fish right in front of the array. The apparent source levels of clicks in the individual tracks increased with range. One individual White-beaked Dolphin and three Harbour Porpoises regulate their output signal level to nearly compensate for one-way transmission loss while approaching a target. The other dolphin regulated the output differently. For most of the recordings the sound level at the target remains nearly constant and the echo level at the animal increases as it closes on the target.

Migraine with aura: visual disturbances and interrelationship with the pain phase. Vågå study of headache epidemiology

In the Vågå study of headache epidemiology, 1838 or 88.6% of the available 18–65-year-old inhabitants of the commune were included. Everyone was questioned and examined personally by the principal investigator (OS). There were 178 cases of various types of visual disturbances during the migraine attack, which corresponds to 9.7% of the study group. The prevalence among females was 11.9% and among males 7.4%; female/male ratio was 1.70, as against 1.05 in the total Vågå study population. By far the most frequently occurring visual disturbance pattern was (A) 1. Visual disturbances → 2. pain-free interlude → 3. pain phase (in 78% of the cases). Other frequent patterns were: (B). Visual disturbances, but no pain phase (24%); and: (C) 1. Pain phase → 2. visual disturbances (23%). Evidently, in the solitary case, there might be more than one visual disturbance pattern. The most frequently occurring solitary visual disturbances were: scintillating scotoma (62%) and obscuration (33%); but also more rare ones were identified, like anopsia, autokinesis (movement of stationary objects), tunnel vision and micropsia. Among the non-visual aura disturbances, paraesthesias and speech disturbances were the most frequent ones. The prevalence of migraine with aura seemed to be considerably higher than in similar studies. This also includes studies that have been carried out with a face-to-face interview technique.

Grading of headache intensity. A proposal

Abstract Current severity (intensity) grading in headache is based upon a 4-grade category scale that includes the zero grade. For ordinary scientific and practical work, a low-sensitivity scale may suffice. However, in given instances, such grading may be insufficient; one might for instance need to know more exactly where the healthy state ends and where headache starts. This may in particular concern epidemiological studies and mass screening. The placement of the “divisory bar” will naturally have a clear impact on the prevalence of headaches, especially the mild ones such as tension-type headache. A 7-step scale is proposed with “excruciating headache” at the top (e.g. cluster headache and chronic paroxysmal hemicrania). Below the mild category of the IHS scale, two categories have been proposed: I, minimal unpleasantness, without any reduction of thriving and without procrastination; and II, discomfort/heaviness with reduction of thriving and procrastination. The bar for discriminating between the healthy state and a headache disorder with an impact upon social life should probably be put between categories I and II on the scale. In situations where increased sensitivity of intensity grading is desirable, such a scale may be useful. This scale has been extensively used during the Vågå study of headache epidemiology, where it has been easy to apply. Consistency tests showed acceptable reproducibility values.

On statistical methods for comparison of intrasample morphometric variability: Zalavár revisited

In studies of morphology, methods for comparing amounts of variability are often important. Three different ways of utilizing determinants of covariance matrices for testing for surplus variability in a hypothesis sample compared to a reference sample are presented: an F-test based on standardized generalized variances, a parametric bootstrap based on draws on Wishart matrices, and a nonparametric bootstrap. The F-test based on standardized generalized variances and the Wishart-based bootstrap are applicable when multivariate normality can be assumed. These methods can be applied with only summary data available. However, the nonparametric bootstrap can be applied with multivariate nonnormally distributed data as well as multivariate normally distributed data, and small sample sizes. Therefore, this method is preferable when raw data are available. Three craniometric samples are used to present the methods. A Hungarian Zalavár sample and an Austrian Berg sample are compared to a Norwegian Oslo sample, the latter employed as reference sample. In agreement with a previous study, it is shown that the Zalavár sample does not represent surplus variability, whereas the Berg sample does represent such a surplus variability.

Whiplash in individuals with known pre–accident, clinical neck status

In whiplash studies, there may be interpretation difficulties: are post–whiplash findings, when present, a consequence of the whiplash trauma, or did they exist prior to trauma? In the Vågå headache epidemiology study (1995–1997), there was a headache history and detailed physical/neurological findings from the face/head/neck in 1838 18–65–year-old parishioners. In September 2001, four years after the Vågå study, a search through the Health Centre files divulged six cases with whiplash trauma in the intervening period. These parishioners could thus be their own controls. Two females did not develop new complaints. In the four parishioners with apparently new, subjective complaints, i. e., headache, neck pain, and a feeling of stiffness in the neck, there were corresponding findings as regards various parameters: shoulder area skin–roll test, changes in two, possible changes in two; range of motion, neck, changes in two, borderline changes in one; “features indicative of cervical abnormality” (“CF”), changes in all four; the mean, post–whiplash stage value was: 3.6+, against 1.6+ prior to accident (Vågå: only 0.93%, “CF” exceeding 3+). In the two without new complaints, the mean “CF” value was 1.0+. The number of cases is small, but the similarity of the symptoms—and signs—following whiplash injury may suggest an element of organic origin in the whiplash syndrome.

Book Review of Paleodemography. Age Distributions from Skeletal Samples. Edited by R. D. Hoppa and J. W. Vaupel. (Cambridge: Cambridge University Press, 2002). [pp. 259]. ISBN: 0 521 80063 3. £60 hdbk.

The present volume is a collection of papers based on two workshops on palaeodemography at the Max Planck Institute for Demographic Research in Rostock in 1999 and 2000. The introductory paper by Hoppa and Vaupel presents the so-called Rostock Manifesto for Paleodemography comprising four elements: (1) development of reliable and validated osteological age indicators, based on skeletal samples with known ages-at-death, (2) development of methods for estimating the probability of observing a specific set of osteological characteristics ‘c’, given known age-at-death ‘a’, i.e. P(c|a), (3) recognition of the fact that P(c|a) 61⁄4P(a|c), the latter being the probability that age-at-death was ‘a’, given an observed set of osteological characteristics ‘c’. P(a|c) is the value human osteologists would want to know, and it should be calculated from P(c|a) using Bayes’ theorem. In order to do this, information about the distribution of ages-at-death, f(a), is needed, and thus, (4) even if it seems self-contradictory, because f(a) is what palaeodemographers specifically want to know, an initial qualified guess at f(a) must be given, later to be modified by appropriate analyses of the actual data. The workshops and thus the present volume have at least in part grown out of a great concern for, or even scepticism towards, palaeodemography in general. One of the main problems with ‘traditional’ palaeodemography is that the distribution of ages-at-death of the samples studied (target samples) is biased towards the distribution of ages-at-death in the samples with known age-at-death on which the osteological age determination methods are based (reference samples). Behind this specific problem there is a number of more intriguing problems, but in essence it is fair to say that traditional palaeodemography is based on a diverse set of ad hoc methods, all of them prone to introduce bias in the demographic parameters and distributions calculated. Furthermore, they do not give proper statistical confidence intervals for individual age-at-death estimates or for demographic parameters. The papers in the present volume are intended to remedy these problems by presenting several interesting attempts to develop model-based and theoretically wellfounded methods for use in palaeodemography. One of the attractive features of traditional palaeodemographic methodology is that not only the osteological methods but also the calculation methods (if any) are quite simple. The osteological methods proposed in the present volume are to a large extent based on procedures used in traditional palaeodemography, and they are in any case not more complicated than the latter. However, when it comes to the calculations used, there is a huge difference. The mathematical models as well as the computer programming algorithms needed in order to do proper palaeodemography are quite complicated and most probably beyond all but the most mathematically inclined human osteologists. This is the most obvious ‘negative’ aspect of the book. If one tries to follow the development of models and formulae in detail, reading is slow and the risk of missing important non-technical messages high. However, even if I regard myself as an at least in part mathematically inclined biological anthropologist, I have tried to read the book also from the perspective of the more general reader, and when doing this a lot of important messages actually get through. Therefore, one can read the book from the perspective of a textbook where certain parts (the more complicated sections and formulae) can be ‘skipped without loss of continuity’. What one could ask for was some user-friendly software with easy-to-read manuals that can be used for doing the analyses proposed. The only specifically palaeodemographic software link indicated is dead. One very essential problem that certainly needs more consideration than it has received in this book—or elsewhere—is the question of uniformitarianism, i.e. the validity of the assumption that age-related changes in the osteological characters employed in ANNALS OF HUMAN BIOLOGY MAY–JUNE 2004, VOL. 31, NO. 3, 374–375