Hearing and Balance Exceed Initial Bone Mineral Density in Predicting Incident Fractures: A 25-Year Prospective Observational Study in Menopausal Women With Osteoporosis

Hearing and balance deteriorate, and fracture incidence increases with age, especially in women. The aim of the present study was to investigate whether impaired hearing and body balance are stronger predictors of fractures than bone mass. Between 1995 and 1997, 80 women, aged 50 to 70 years, with primary osteoporosis, taking menopausal hormone therapy, mainly for menopausal symptoms, participated in a double-blind, randomized, placebo-controlled study of treatment with growth hormone versus placebo. All women received calcium 750 mg and vitamin D 400 U daily. They were then examined yearly until 2007 and followed up by registers until 2020. Hearing was assessed by audiometry. Body balance and fine motor function were tested according to the Bruininks-Oseretsky test. Bone properties were measured with DXA. Data on fractures were derived from the Gothenburg Hospital register. Over the 25-year follow-up, 50 women (63%) sustained 104 fractures, most often related to accidental falls. Thoracic and lumbar spine fractures were most common (36%). Other fractures occurred in the pelvis (14%), humerus (14%), hip (11%), and wrist (10%). Hearing impairment at baseline, measured as pure tone average-high (p = 0.007), pure tone average-mid (p = 0.003), and speech-recognition score (p = 0.025), was associated with a subsequent first fracture, as were worse body balance (p = 0.004), upper limb coordination (p = 0.044), and higher running-speed agility (p = 0.012). After adjustment for age and BMD, pure tone average-high (p = 0.036), pure tone average-mid (p = 0.028), and body balance (p = 0.039) were still significantly associated with incident fractures. Bone mineral content, BMD, and treatment at baseline were not associated with subsequent fracture. In conclusion, hearing and body balance at baseline exceeded initial BMD in predicting incident fractures in osteoporotic women regardless of treatment during 25-year follow-up. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

The responses of single units of the inferior colliculus of the cat to acoustic stimulation

Discharges of single units of the inferior colliculus in response to acoustic stimulation have been studied in anaesthetized and decerebrate cats by means of extracellularly placed electrodes. A tonal stimulus may cause a unit to discharge either with a short burst of spikes or with a slowly adapting train of spikes. For each unit there is a ‘characteristic frequency’ at which the threshold is lowest, with rising thresholds for frequencies on either side. In response to tonal stimuli presented to one ear, some units (classed as Group A units) may respond over a relatively wide range of the audible spectrum, while other units (classed as Group B units) are only activated by tonal frequencies within a narrow band of the spectrum. Some Group B units, however, may be activated by two separate bands of frequencies at different parts of the spectrum; this occurs even though the unit can only be activated by stimuli delivered to one ear. An increase in the intensity of the stimulus causes an increase in the rate of firing of the unit, and also a broadening in the range of tonal frequencies which can activate the unit. This takes place to a greater extent for Group A units than for Group B units. Masking of the unitary responses to clicks by different tonal backgrounds was examined. A click response may be abolished by a particular tonal frequency: on either side of this frequency the characteristics of the responses (i. e. the mean latency and number of spikes per discharge) are altered. This may take place over a large or small range of the audible spectrum. Tonal stimuli delivered to either ear may activate the same unit. In such cases, the unit may have two ‘characteristic frequencies’, but these lie close to one another. The range of tonal frequencies which activates the unit, however, differs for the two sides. Click stimulation alone presented to either ear may activate the same unit. When click stimuli are delivered in succession to the two ears, there is revealed an absolutely unresponsive period during which the second stimulus cannot evoke a detectable response. The duration of this unresponsive period is dependent upon which ear is stimulated first, and is not the same for the two sides. For most units, the absolutely unresponsive period was longer when the contralateral ear was stimulated first. With progressive increase in the interval between the two stimuli there is a relatively unresponsive period during which the characteristics of the responses are altered, until finally a constant response to the second stimulus is obtained. If the two stimuli are separated by short intervals, summation of the two responses may take place. When the sound source is moved in a semicircular horizontal plane in front of the head, and click stimuli are delivered at every 15°, an asymmetrical distribution with respect to the latency is revealed. For those units which are activated by click stimuli delivered to either ear, a progressive and linear change in the mean latency of the response occurs as the source is moved from one ear to the opposite ear. When the sound source is placed at the midline, however, there is a deviation from the linear relationship and the mean latency is significantly decreased. This decrease does not occur for responses from units activated by stimuli presented to one ear alone. The significance of these findings is discussed, particularly in relation to central mechanisms for the localization of sound in space.

Auditory pain thresholds for intermittent, "beat" and steady signals

Eight Ss were given audiograms and ear examinations to insure normality and then presented with a series of tones at either 1000 cps or 2500 cps. For each frequency the sounds were presented as constant tones, as interrupted pulses, or as “beats,” the pulses and beats being given at repetition rates of either 3, 6, or 15 per sec. For each condition the intensity of the sound was increased by a series of steps. S was to indicate when the tone was “just noticeably unpleasant” (JNU) and when it was “just noticeably painful” (JNP). These thresholds were measured in terms of the db attenuation from a given maximum of 130 ± 2 db. It was found that individual pain thresholds varied from about 100 db to over 130 db, with unpleasantness thresholds about 8 to 10 db below pain thresholds. The 2500-cps signal, irrespective of whether it is presented as a steady stimulus, a series of pulses, or a series of beats, is reacted to as “unpleasant” or as “painful” at a slightly, but consistently lower intensity level than the corresponding 1000-cps tone. At each frequency used, intermittent tones are judged as “unpleasant” or “painful” at lower intensity levels than steady tones. The differences are slight but consistent. Repetition rates of three pulses or beats per second were fairly consistently found to have a lower unpleasantness and pain threshold than either 6 or 15 per sec. In general, pain thresholds seemed to be related primarily to power per pulse, rather than total energy in a series of pulses.

Methods and findings in an analysis of a vocal operant

The relations among acoustic parameters of a vocal operant were considered and some methods for their measurement are described. Four human subjects (Ss) and one chick were employed in an experiment on the relations among vocal rate, vocal topography, and schedules of reinforcement. The earlier finding that schedules of reinforcement control human and infra-human vocal responding as they do other operants was replicated and extended to the case of variable-interval reinforcement. An analysis of response amplitude, pitch, and duration showed that the mean and variance of these parameters typically increase from CRF to VI, from VI to EXT and, for a second group of Ss, from CRF to EXT. The topography of the chick's vocal response appears to stand in the same relation to reinforcement operations as does the human vocal response.

Size and reliability of frequency-difference thresholds determined with operant tracking procedure

Auditory frequency discrimination thresholds have been determined by a "tracking procedure" at five frequencies and two intensity levels for a group of four cats. Intra-animal thresholds were found to be quite stable, and there was good inter-animal agreement among three of the four cats. Although quite stable, the tracking thresholds were larger than those which had been obtained using an avoidance procedure. However, because of the several differences between the tracking procedure and avoidance conditioning procedure, no conclusions can be drawn concerning the efficacy of the different types of reinforcement in determining the ultimate limit of the animals' discrimination ability.

On the discriminative control of concurrent responses: the relations among response frequency, latency, and topography in auditory generalization

Human subjects were used in a study of auditory generalization following multiple-response discrimination training. The relations observed among stimulus intensity, response probability, and response latency were invariant with respect to whether the two vocal responses conditioned were topographically discrete, as in one experiment, or topographically continuous, as in another. The major findings were:1. The probabilities associated with a specific response were maximal over several stimulus values at the extreme ends of the continuum, then dropped sharply at stimuli intermediate to the initial S(D)'s as the probability of the alternative response increased.2. Overall response latency was inversely related to the relative frequency of the two responses at each stimulus value. When the two responses were most nearly equal in probability, latencies were maximal; when one response had close to unit or zero probability, latencies were minimal.3. Analysis of the latencies of the two responses, taken separately, revealed: (a) an increase in latency as the difference between the test stimulus and the initial S(D) increased; (b) a sharp discontinuity in the latency gradient and reversal in trend at intermediate stimulus intensities; and (c) at a given stimulus value, latencies associated with the stochastically dominant response were consistently shorter than those of the nondominant response.4. No changes in response topography (fundamental frequency) were correlated with the characteristic changes in probability and latency during stimulus generalization.

Generalization gradients of inhibition following auditory discrimination learning

A more direct method than the usual ones for obtaining inhibitory gradients requires that the dimension of the nonreinforced stimulus selected for testing be orthogonal to the dimensions of the reinforced stimulus. In that case, the test points along the inhibitory gradient are equally distant from the reinforced stimulus. An attempt was made to realize this condition by obtaining inhibitory gradients along the frequency dimension of a pure tone after discrimination training in which the nonreinforced stimulus was a pure tone (or tones), and the reinforced stimulus was either white noise or the absence of a tone. The results showed that some degree of specific inhibitory control was exerted by the frequency of the tone, although the gradients were broad and shallow in slope.A further experiment was conducted to see whether the modification of an excitatory gradient resulting from training to discriminate neighboring tones could arise from a simple interaction of inhibitory and excitatory gradients. The results indicated that it could not, since discrimination training produced a concentration of responding in the vicinity of the reinforced stimulus which cannot be derived from any plausible gradient of inhibition.