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L H Larsen

Publications and source records attributed to L H Larsen.

At least 19 recordsLinked to original sources
PubMed1998

Growth hormone in postmenopausal women after long-term oral estrogen replacement therapy.

Studies of estrogen effects on growth hormone (GH) and its pulsatile release in postmenopausal women have typically utilized estrogen replacement therapy (ERT) of relatively short duration (days to weeks). The purpose of this study was to compare GH measures from healthy postmenopausal women who were on oral ERT for 3 years or more (n = 24; mean ERT duration = 16.1 years) with women not on ERT (NERT; n = 40). Blood samples were drawn remotely every 20 min for 24 h and then analyzed for mean 24-h GH, mean GH during sleep, and mean 24-h insulin-like growth factor-I (IGF-I). GH peak analyses were also performed. Mean 24-h GH and GH during sleep were significantly higher and IGF-I was significantly lower in ERT women compared with NERT women. In addition, use of long-term ERT was associated with more GH peaks relative to women not on ERT, but no change in GH peak amplitude or area. GH was not related to age in either group. GH was strongly and negatively correlated with measures of adiposity in NERT women but not in ERT women. In conclusion, long-term oral ERT is associated with increased circulating GH and decreased IGF-I levels, even after many years of treatment.

Administration, Oral↗
PubMed1997

Circadian temperature and cortisol rhythms during a constant routine are phase-delayed in hypersomnic winter depression.

Circadian temperature, cortisol, and thyroid-stimulating hormone (TSH) rhythms during a constant routine were assessed in 6 female controls and 6 female patients with hypersomnic winter depression (seasonal affective disorder, SAD) before and after morning bright light treatment. After sleep was standardized for 6 days, the subjects were sleep-deprived and at bed rest for 27 hours while rectal temperature, cortisol, and TSH levels were assessed. The minimum of the fitted rectal temperature rhythm was phase-delayed in the SAD group compared to the controls 5:42 AM vs. 3:16 AM (p < .005); with bright light treatment, the minimum advanced from 5:42 AM to 3:36 AM (p = .06). The minimum of the cortisol rhythm was phase-delayed in the SAD group compared to the control group, 12:11 AM vs. 10:03 PM (P < .05); with bright light treatment, the minimum advanced from 12:11 AM to 10:38 PM (P = .06) [corrected]. The acrophase of the TSH rhythm was not significantly phase-delayed in SAD subjects compared to control, though the trend appeared to be toward a phase-delay (p = .07). After bright light therapy, the TSH acrophase was not significantly different in the SAD subjects; the trend was a phase-advance (p = .09). Overall, the data suggest that circadian rhythms are phase-delayed relative to sleep in SAD patients and that morning bright light phase-advances those rhythms.

Adult↗
PubMed1996

Objective sleep quality of healthy older men and women is differentially disrupted by nighttime periodic blood sampling via indwelling catheter.

Elucidation of sleep-endocrine relationships requires frequent blood sampling during sleep recording. Unfortunately, such sampling can itself affect sleep and indirectly, hormonal patterns. We examined the effect of catheterization and frequent nighttime blood sampling on the sleep of a large sample of healthy older men and women. A total of 113 healthy older [69.1 +/- 0.6 years, mean +/- standard error of the mean (SEM) adults (68 women and 45 men) were studied. Following an adaptation night sleep was recorded during an undisturbed night and a night of periodic blood sampling via i.v. catheter. Lights out and lights on were significantly delayed and advanced, respectively, on the catheterization night, resulting in a significantly shorter time in bed (TIB). Total sleep time and sleep efficiency were significantly reduced, and sleep latency, total wake time and the number of awakenings from sleep of > or = 1 minute were significantly increased. Rapid eye movement (REM) sleep percentage of TIB was significantly reduced. Stages 3/4 sleep [slow wave sleep (SWS)] percentage of TIB was significantly reduced, as was total delta energy during SWS. With the exception of total sleep time and sleep latency, all sleep-wake and delta variables were significantly correlated between nights. This was particularly the case for SWS and the delta energy variables. When examined separately by gender, both men and women showed significant catheter-based sleep disturbance. However, SWS and delta energy measures in men were unaffected by catheterization. The data clearly demonstrate that both the sleep maintenance and sleep architecture of healthy older men and women are significantly impacted by nighttime blood sampling procedures. Of the various measures examined here, SWS measures appear to be the least disrupted, particularly in men. These findings need to be taken into account in any study examining sleep-endocrine relationships utilizing older subjects.

Aged↗
PubMed1996

Structure and function of a nitrifying biofilm as determined by in situ hybridization and the use of microelectrodes.

Microprofiles of O2 and NO3- were measured in nitrifying biofilms from the trickling filter of an aquaculture water recirculation system. By use of a newly developed biosensor for NO3-, it was possible to avoid conventional interference from other ions. Nitrification was restricted to a narrow zone of 50 microns on the very top of the film. In the same biofilms, the vertical distributions of members of the lithoautotrophic ammonia-oxidizing genus Nitrosomonas and of the nitrite-oxidizing genus Nitrobacter were investigated by applying fluorescence in situ hybridization of whole fixed cells with 16S rRNA-targeted oligonucleotide probes in combination with confocal laser-scanning microscopy. Ammonia oxidizers formed a dense layer of cell clusters in the upper part of the biofilm, whereas the nitrite oxidizers showed less-dense aggregates in close vicinity to the Nitrosomonas clusters. Both species were not restricted to the oxic zone of the biofilm but were also detected in substantially lower numbers in the anoxic layers and even occasionally at the bottom of the biofilm.

Biofilms↗
PubMed1995

Higher plasma IGF-1 levels are associated with increased delta sleep in healthy older men.

BACKGROUND: Sleep quality declines with age, with less time in deep or slow wave sleep (SWS) and reduced amplitude of the delta waves that characterize it. Age-related declines also occur in lean body mass, growth hormone (GH), and insulin-like growth factor 1 (IGF-1). These changes in sleep quality and anabolic status may be related, as administration of GH or growth hormone releasing hormone (GHRH) can enhance SWS and decrease awakenings in young men. Here we examine the relationship between plasma IGF levels and delta sleep quality in older men. METHODS: The sleep EEG of 30 healthy elderly men (64 +/- 6 yrs; range 50-75) was recorded on the second of 2 consecutive nights. Plasma samples were drawn within 3 weeks of EEG recording, and IGF levels were assayed by RIA after acid extraction. RESULTS: IGF explained 28% (semi-partial correlation coefficient r = .53; p = .003) of the variance in average delta energy per epoch of SWS, after age-related variance was removed. Higher IGF was associated with higher average delta energy. Similar results were obtained for total delta energy during SWS (r = .37, p = .04) 4nd time spent in SWS (r = .42, p = .02). Other measures of sleep quality (e.g., wakefulness, REM sleep) were not correlated with IGF. The IGF delta relationship was minimally influenced by moderator variables such as thyroxine (T3, T4), and/or body mass index (BMI). CONCLUSION: We conclude that age-adjusted IGF levels in healthy senior men co-vary significantly with SWS and the delta energy that characterizes it.

Aged↗
PubMed1995

Exercises for chronic low back pain: a clinical trial.

Different training models are effective for the treatment of chronic low back pain, but no consensus has been found. Earlier studies have emphasized training of spinal mobility and back strength. To evaluate if other physiological parameters, such as coordination, are of equal importance, we performed a randomized trial on 40 consecutive patients with chronic low back pain. Two training models were compared: 1) intensive training of muscle endurance and 2) muscle training, including coordination. In both groups, training was performed 1 hour twice a week for 3 months. Pain score, disability score, and spinal mobility improved in both training groups without differences between the two groups. Only intensive training of muscle endurance improved isokinetic back muscle strength. At study entry, we found a significant correlation between spinal mobility and dysfunction, but after the training, no correlation was found between improvement of spinal mobility or isokinetic back extension strength and improvement of function or pain level. We conclude that coordination training for patients with chronic low back pain is as equally effective as endurance training.

Adolescent↗
PubMed1995

A note on the night-to-night stability of stages 3 + 4 sleep in healthy older adults: a comparison of visual and spectral evaluations of stages 3 + 4 sleep.

Night-to-night variability in the minutes of slow-wave sleep (SWS: combined minutes of stages 3 and 4 sleep) was examined for 50 healthy adults: 23 women (56-82 years old) and 27 men (54-74 years old). Visually rated SWS was more variable night to night than computer-evaluated SWS using power spectral techniques. The night-to-night correlation of the visually rated SWS was 0.61. The night-to-night correlation of the spectrally evaluated SWS was 0.91.

Aged↗
PubMed1994

C STAGE, automated sleep scoring: development and comparison with human sleep scoring for healthy older men and women.

Using the sleep records of 200 men and women (age 55-85 years), we have developed a human-assisted computer scoring system, C STAGE. The system can have many applications, including quantitative electroencephalographic (EEG) analysis during specific stages of sleep. C STAGE classifies sleep/wake stages using power spectral analysis and other techniques applied to one channel of EEG data. Here we report comparability data between C STAGE- and human-rated sleep-stage scoring using Rechtschaffen and Kales criteria for 70 normal subjects (a subset of the 200). Because the method was developed using these subjects, we also report comparability data for an independent validation sample of 45 normal older men and women. For waking measures, sleep stages 3 and 4, and total sleep time, C STAGE yielded ratings comparable with the human rater (r = 0.73-0.91; p < 0.001). For sleep stages 1 and 2 and REM sleep, C STAGE correlated less well with human ratings (r = 0.59-0.81; p < 0.001). Overall, these correlations compare well with other currently available computer stage-scoring methods. Epoch-by-epoch comparisons in the validation sample revealed a mean proportion of agreement of 0.74 and a mean Kappa coefficient of 0.57, indicating the two methods provide reasonable agreement on an epoch-by-epoch basis. We conclude that C STAGE is a valid sleep/waking scoring system for healthy older adults.

Aged↗
PubMed1993

Major unipolar depression and mild Alzheimer's disease: differentiation by quantitative tonic REM EEG.

In a previous report, tonic REM sleep epochs from the all-night sleep EEG were processed and analyzed to produce a diagnostic that discriminated mild Alzheimer's disease (AD) from cognitively unimpaired control subjects. Here, we examine the specificity of this diagnostic in distinguishing depression from AD. Twenty-four cognitively unimpaired seniors (aged 63 +/- 1.3) with major depressive disorder (unipolar) were monitored for all-night EEG in a manner identical to that used in our previous report. Tonic REM EEG epochs were preconditioned, spectrally analyzed and compared with known populations of control and AD EEG spectra. Instances when a given depressed subject's spectra fell within spectral zones unique to control or AD populations formed a diagnostic score (control, AD, neither of these). Diagnostic scores correctly identified 88% (21/24) of cognitively unimpaired seniors with major depressive disorder (unipolar). This can be compared with 89% (31/35) of mild AD subjects and 100% (43/43) of control subjects correctly identified in our previous report. This diagnostic also correctly classified as to eventual clinical AD/not AD outcome 8 subjects with both major depressive disorder and validated memory complaints. The diagnostic discrimination of AD is based on the fact that AD subjects have significantly less tonic REM EEG energy in the 13-30 Hz frequency range and more in the 1-10 Hz range than control or depressed subjects, as shown in conventional spectral analysis.

Aged↗
PubMed1993

Dim light melatonin onset and circadian temperature during a constant routine in hypersomnic winter depression.

The onset of melatonin secretion under dim light conditions (DLMO) and the circadian temperature rhythm during a constant routine were assessed in 6 female controls and 6 female patients with winter depression (seasonal affective disorder, SAD) before and after bright light treatment. After sleep was standardized for 6 days, the subjects were sleep-deprived and at bedrest for 27 h while core temperature and evening melatonin levels were determined. The DLMO of the SAD patients was phase-delayed compared with controls (2310 vs 2138); with bright light treatment, the DLMO advanced (2310 to 2135). The minimum of the fitted rectal temperature rhythm was phase-delayed in the SAD group compared with the controls (0542 vs 0316); with bright light treatment, the minimum advanced (0542 vs 0336).

Adult↗
PubMed1992

Quantitative analysis of the EEG during tonic REM sleep--methodology.

Frequency and amplitude characteristics of the clinical (waking) electroencephalogram (EEG) can be diagnostically useful in neuronal degenerative disorders such as Alzheimer's or other cortical dementias. However, interpretation of the clinical EEG may be limited by many factors, including movement and muscle artifacts and uncontrolled variations along the alert/drowsy continuum. Moreover, the clinical EEG involves subjective judgement by experts whose opinions often differ. In an effort to address these problems, we have developed a computer-automated technology that examines the digitized, all-night sleep EEG for frequency and amplitude characteristics of potential diagnostic relevance to Alzheimer's dementia. Robust time series analysis techniques and a modified power spectral analysis (Z-spectra) are used to suppress artifactual information and to automatically select samples of tonic REM sleep EEG. The spectra (amplitude vs. frequency relationship) of this specific EEG state is then assessed for diagnostically relevant information.

Algorithms↗
PubMed1992

EEG markers of early Alzheimer's disease in computer selected tonic REM sleep.

All night sleep/wake EEGs were examined for diagnostic features sensitive to early Alzheimer's disease (AD) using computer automated techniques. Thirty-nine mild AD patients and 43 normal controls underwent 9 h of EEG recording in the sleep laboratory. All-night EEGs were screened for ideal, low artifact tonic REM sleep using autoregressive and power spectral techniques. The frequency spectra during tonic REM sleep revealed a significant shift towards slower wave forms in AD vs. control subjects. Beta (greater than 12 Hz) was reduced and theta and delta (2-8 Hz) increased in AD compared to control groups. This frequency shift was demonstrated by several analytic techniques, including binned spectral energies and unique zones in the frequency spectra. Discriminant analyses using optimal binned EEG variables correctly classified 74% of AD and 98% of control subjects, and unique zone scores correctly classified 92% of AD and 95% of control subjects, indicating that these sleep EEG changes are apparently predictive of AD status.

Aged↗
PubMed1991

EKG artifacts suppression from the EEG.

A method is proposed to identify and eliminate EKG artifacts from a single channel of EEG recordings. The method identifies the EKG as outlying data in the EEG. The algorithm may be applied universally to all EEG recordings.

Algorithms↗
PubMed1991

Healthy elderly women and men have different entrained circadian temperature rhythms.

Body core temperature was measured in healthy elderly men and women under entrained conditions. Female subjects showed a larger amplitude and a higher peak temperature than male subjects. In addition, acrophase was advanced for females by an average of 49 minutes. Variability in acrophase was greater for males than females. This pattern of gender differences varies considerably from the pattern others have observed in young subjects, suggesting that aging may affect the circadian timing system of males and females differently.

Aged↗
PubMed1979

Age and sex specific reference limits for carbohydrate tolerance.

Glucose estimations in the absence of diabetic symptoms may lead to diagnostic problems when clinicians are confronted with borderline results. This study on 28 581 estimations of post-prandial plasma glucose values gives age and sex specific reference limits derived from regression analysis at the 97.5 percentage point. A linear relationship exists between age and glucose tolerance in both sexes which is affected by the time of specimen collection. No evidence was found in support of bimodality; hence, it is believed that the observed diminution of carbohydrate tolerance with age is characteristic of the entire population.

Adult↗
PubMed1979

Evaluation of automated multiphasic health testing in the survey of the north-west region of Melbourne.

The results of automated multiphasic health testing (AMHT) in a randomly selected population of 664 subjects are reported. AMHT revealed a number of conditions that had not been diagnosed previously. A total of 535 newly diagnosed conditions in 301 patients could be attributed to the survey. The yield of new diagnoses by AMHT was not affected by previous surgery attendance or by attendance intervals. Follow-up over one year revealed that treatment was recommended for 342 of the 535 newly diagnosed conditions and that the response was satisfactory in 189 (55%), but the "uncertain" response of 124 (36%) should be investigated by more thorough follow-up in future projects. It is concluded that AMHT is beneficial because of the amount of information that is revealed, because of the financial value and because of the benefit to patients.

Adult↗