Increase in upper extremity fractures in young male soccer players in the Netherlands, 1998-2009.

Young male soccer players have been identified as a target group for injury prevention, but studies addressing trends and determinants of injuries within this group are scarce. The goal of this study was to analyze age-specific trends in hospital-treated upper extremity fractures (UEF) among boys playing soccer in the Netherlands and to explore associated soccer-related factors. Data were obtained from a national database for the period 1998-2009. Rates were expressed as the annual number of UEF per 1000 soccer players. Poisson's regression was used to explore the association of UEF with the number of artificial turf fields and the number of injuries by physical contact. UEF rates increased significantly by 19.4% in boys 5-10 years, 73.2% in boys 11-14 years, and 38.8% in boys 15-18 years old. The number of injuries by physical contact showed a significant univariate association with UEF in boys 15-18 years old. The number of artificial turf fields showed a significant univariate association with UEF in all age groups, and remained significant for boys aged 15-18 years in a multivariate model. This study showed an increase of UEF rates in boys playing soccer, and an independent association between artificial turf fields and UEF in the oldest boys.

Randomised comparison of three tools for improving compliance with occlusion therapy: an educational cartoon story, a reward calendar, and an information leaflet for parents.

BACKGROUND: We previously demonstrated that compliance with occlusion therapy for amblyopia was improved by the use of an educational programme, especially in children of parents of foreign origin and who spoke Dutch poorly. The programme consisted of: (i) a cartoon story for amblyopic children that explained without words why they should patch, (ii) a calendar with reward stickers, and (iii) an information leaflet for parents. In the current study, we assessed the individual effect of each component on compliance. METHODS: We recruited 120 3- to 6-year-old children who lived in a low socio-economic status (SES) area in The Hague and were starting occlusion therapy for the first time. They were randomised to receive one of the components (three intervention groups), or a picture to colour (control group). The randomisation was blinded for treating orthoptist and researcher. Compliance was measured electronically using the Occlusion Dose Monitor (ODM). Primary outcome was percentage of compliance (actual/prescribed occlusion time). Secondary outcome was absolute occlusion hours per day. Parental fluency in Dutch was rated on a five-point scale. RESULTS: Compliance could be measured electronically in 88 of the 120 children; in 32 others, it failed for various reasons. Parental fluency in Dutch was moderate or worse in 36.4 % (p = 0.327). Average compliance was 55 % standard deviation (SD) 40 (n = 18) in the control group, 89 % SD 25 in the group receiving the educational cartoon (n = 25, P = 0.002 compared with control group), 67 % SD 33 (n = 24, P = 0.301) in the reward-calendar group and 73 % SD 40 (n = 21, P = 0.119) in the parent-information-leaflet group. On average, children in the control group occluded 1:46 SD1:19 hours/day, 2:33 SD 1:18 hours/day in the group receiving the educational cartoon, 1:59 SD 1:13 hours/day in the reward-calendar group and 2:18 SD 1:13 hours/day in the parent-information-leaflet group. No child who received the cartoon story occluded less than 1 hour per day, against seven in the reward-calendar group, five in the parent-information-leaflet group and five in the control group. CONCLUSIONS: Although all three components of the programme improved compliance with occlusion therapy in children in low-SES areas, the educational cartoon had the strongest effect, as it explained without words to a 4- to 5-year-old child why it should wear the eye patch.

Long-term effects of lung cancer computed tomography screening on health-related quality of life: the NELSON trial.

The long-term effects of lung cancer computed tomography (CT) screening on health-related quality of life (HRQoL) have not yet been investigated. In the Dutch-Belgian Randomised Lung Cancer Screening Trial (NELSON trial), 1,466 participants received questionnaires before randomisation (T0), 2 months after baseline screening (screen group only; T1) and at 2-yr follow-up (T2). HRQoL was measured as generic HRQoL (12-item short-form questionnaire and EuroQoL questionnaire), anxiety (Spielberger State-Trait Anxiety Inventory) and lung cancer-specific distress (impact of event scale (IES)). Repeated measures of ANOVA were used to analyse differences between the screen and control groups, and between indeterminate (requiring a follow-up CT) and negative screening result groups. At T0 and T2 there were no significant differences in HRQoL scores over time between the screen and control groups, or between the indeterminate or negative second-round screening result group. There was a temporary increase in IES scores after an indeterminate baseline result (T0: mean 4.0 (95% CI 2.8-5.3); T1: mean 7.8 (95% CI 6.5-9.0); T2: mean 4.5 (95% CI 3.3-5.8)). At 2-yr follow-up, the HRQoL of screened subjects was similar to that of control subjects, the unfavourable short-term effects of an indeterminate baseline screening result had resolved and an indeterminate result at the second screening round had no impact on HRQoL.

Impaired lung compliance and DL,CO but no restrictive ventilatory defect in sarcoidosis.

Sarcoidosis is a systemic granulomatous disease with predominant manifestation in the lungs, often presenting as interstitial lung disease. Pulmonary function abnormalities in sarcoidosis include restriction of lung volumes, reduction in diffusing capacity of the lung for carbon monoxide (D(L,CO)), reduced static lung compliance (C(L,s)) and airway obstruction. The aim of the present study was to assess various lung function indices, including C(L,s) and D(L,CO), as markers of functional abnormality in sarcoidosis patients. Results from 830 consecutive patients referred for lung function tests with a diagnosis of sarcoidosis (223 in stage I, 486 in stage II and 121 in stage III) were retreospectively analysed. The mean ± sd age of the patients was 40 ± 11 yrs; 18% were active smokers and 24% were former smokers. Normal total lung capacity was found in 772 (93%) patients. Of these cases, 24.5% had a low C(L,s) and 21.5% had a low D(L,CO). At least one abnormality was observed in 39.3% of these patients, whereas, in restrictive patients, this figure was 88%. Airway obstruction was present in 11.7% of cases. Lung volumes usually remain within the normal range and measurement of either C(L,s) or D(L,CO) often reveal impaired lung function in sarcoidosis patients, even when their lung volumes are still in the normal range; these two measurements provide complementary information.

Short-term health-related quality of life consequences in a lung cancer CT screening trial (NELSON).

BACKGROUND: In lung cancer CT screening, participants often have an indeterminate screening result at baseline requiring a follow-up CT. In subjects with either an indeterminate or a negative result after screening, we investigated whether health-related quality of life (HRQoL) changed over time and differed between groups in the short term. METHODS: A total of 733 participants in the NELSON trial received four questionnaires: T0, before randomisation; T1, 1 week before the baseline screening; T2, 1 day after the screening; and T3, 2 months after the screening results but before the 3-month follow-up CT. HRQoL was measured as generic HRQoL (the 12-item Short Form, SF-12; the EuroQol questionnaire, EQ-5D), anxiety (the Spielberger State-Trait Anxiety Inventory, STAI-6), and lung-cancer-specific distress (the Impact of Event Scale, IES). For analyses, repeated-measures analysis of variance was used, adjusted for covariates. RESULTS: Response to each questionnaire was 88% or higher. Scores on SF-12, EQ-5D, and STAI-6 showed no clinically relevant changes over time. At T3, IES scores that were clinically relevant increased after an indeterminate result, whereas these scores showed a significant decrease after a negative result. At T3, differences in IES scores between the two baseline result groups were both significant and clinically relevant (P<0.01). CONCLUSION: This longitudinal study among participants of a lung cancer screening programme showed that in the short term recipients of an indeterminate result experienced increased lung-cancer-specific distress, whereas the HRQoL changes after a negative baseline screening result may be interpreted as a relief.

Major improvements in health-related quality of life during the use of etanercept in patients with previously refractory juvenile idiopathic arthritis.

OBJECTIVE: To evaluate changes in health-related quality of life (HRQoL) in patients with refractory juvenile idiopathic arthritis (JIA) who are being treated with etanercept. METHODS: 53 patients with JIA from seven Dutch centres were included. HRQoL was measured by the Childhood Health Assessment Questionnaire (CHAQ), Child Health Questionnaire (CHQ) and Health Utilities Index mark 3 (HUI3) at the start and after 3, 15 and 27 months of treatment. At the same time points the following JIA disease activity variables were collected; physician's global assessment through the visual analogue scale (VAS), number of active and limited joints and erythrocyte sedimentation rate. A statistical method linear mixed models was used to assess outcomes over time. RESULTS: During etanercept treatment both disease-specific and generic HRQoL outcomes improved dramatically. Significant improvements were shown after 3 months and these improvements continued at least up to 27 months of treatment. The disease-specific CHAQ, including VAS pain and wellbeing, showed a significant improvement in all domains. The generic health-profile measure CHQ improved for all the health concepts except for "family cohesion", which was normal. The generic preference-based HUI3 showed impairment and, subsequently, significant improvement in the more specific domains ("pain", "ambulatory", "dexterity"). In accordance disease activity variables also improved significantly over time. CONCLUSION: This study shows that the HRQoL of patients with refractory JIA can be substantially improved by the use of etanercept for all aspects impaired by JIA. Information on HRQoL is crucial to understand the complete impact of etanercept treatment on patients with JIA and their families.

A cluster of hepatitis B infections associated with incorrect use of a capillary blood sampling device in a nursing home in the Netherlands, 2007.

In July 2007, two residents of a nursing home were diagnosed with acute Hepatitis B virus infection. To identify risk factors for HBV infection a retrospective cohort study among residents was performed. Case finding included discharged diabetes patients and those receiving home care. Among 32 residents one case of chronic hepatitis B was found that could be identified by genotyping as the source patient for the acute cases. Diabetes and finger sticks were risk factors for HBV infection. Most likely the cause of transmission was a multiclix finger stick device developed for use in individual patients but used in multiple patients. Education and training in the use of new equipment and hygiene audits remain the cornerstones in infection control practices.

Ethnic differences in prenatal growth and the association with maternal and fetal characteristics.

OBJECTIVES: The objectives of this study were to determine ethnic differences in prenatal growth and to examine their association with differences in maternal and fetal characteristics such as maternal height, weight, age, parity and fetal gender. METHODS: A total of 1494 women from Rotterdam, The Netherlands, with a low-risk pregnancy who participated in a population-based cohort study, the Generation R Study, were offered three ultrasound examinations during pregnancy. Multilevel modeling was applied to determine ethnic differences in (estimated) fetal weight (including birth weight) and in the separate biometric variables that were used to calculate the estimated fetal weight (abdominal circumference, head circumference and femur length). Additionally the association of ethnic differences with maternal and fetal characteristics (i.e. maternal weight, height, age, parity and fetal gender) was studied. RESULTS: Turkish, Cape Verdian, Surinamese-Creole and Surinamese-Hindustani women had on average smaller fetuses than the native Dutch women. The differences became more pronounced towards term. In the Turkish group the differences were no longer statistically significant when adjusted for maternal weight, height, age, parity and fetal gender. In the Cape Verdian, Surinamese-Creole and Surinamese-Hindustani groups the differences decreased after adjustment (31%, 16% and 39%, respectively). CONCLUSIONS: This study shows that there are ethnic differences in fetal growth, which to a large extent may be attributed to differences in maternal weight, height, age and parity. For some ethnic groups, however, additional factors are involved, as differences remain significant after correction for fetal and maternal characteristics.

Effects of meteorological factors on epidemic malaria in Ethiopia: a statistical modelling approach based on theoretical reasoning.

This study was conducted to quantify the association between meteorological variables and incidence of Plasmodium falciparum in areas with unstable malaria transmission in Ethiopia. We used morbidity data pertaining to microscopically confirmed cases reported from 35 sites throughout Ethiopia over a period of approximately 6-7 years. A model was developed reflecting biological relationships between meteorological and morbidity variables. A model that included rainfall 2 and 3 months earlier, mean minimum temperature of the previous month and P. falciparum case incidence during the previous month was fitted to morbidity data from the various areas. The model produced similar percentages of over-estimation (19.7% of predictions exceeded twice the observed values) and under-estimation (18.6%, were less than half the observed values). Inclusion of maximum temperature did not improve the model. The model performed better in areas with relatively high or low incidence (>85% of the total variance explained) than those with moderate incidence (55-85% of the total variance explained). The study indicated that a dynamic immunity mechanism is needed in a prediction model. The potential usefulness and drawbacks of the modelling approach in studying the weather-malaria relationship are discussed, including a need for mechanisms that can adequately handle temporal variations in immunity to malaria.

Impact of screening for breast cancer in high-risk women on health-related quality of life.

The effectiveness of intensive surveillance in women at high risk for breast cancer due to a familial or genetic predisposition is uncertain and is currently being evaluated in a Dutch magnetic resonance imaging (MRI) screening (MRISC) study, in which annual imaging consists of mammography and MRI. Unfavourable side effects on health-related quality of life may arise from this screening process. We examined the short-term effects of screening for breast cancer in high-risk women on generic health-related quality of life and distress. A total of 519 participants in the MRISC study were asked to complete generic health-status questionnaires (SF-36, EQ-5D) as well as additional questionnaires for distress and items relating to breast cancer screening, at three different time points around screening. The study population showed significantly better generic health-related quality of life scores compared to age-/sex-adjusted reference scores from the general population. Neither generic health-related quality of life scores nor distress scores among the study sample (n=334) showed significant changes over time. The impact of the screening process on generic health status did not differ between risk categories. Relatively more women reported mammography as quite to very painful (30.1%) compared to MRI. Anxiety was experienced by 37% of the women undergoing MRI. We conclude that screening for breast cancer in high-risk women does not have an unfavourable impact on short-term generic health-related quality of life and general distress. In this study, high-risk women who opted for regular breast cancer screening had a better health status than women from the general population.

Assessing density dependence in the transmission of lymphatic filariasis: uptake and development of Wuchereria bancrofti microfilariae in the vector mosquitoes.

Understanding density dependence in the transmission of lymphatic filariasis is essential for assessing the prospects of elimination. This study seeks to quantify the relationship between microfilaria (Mf) density in human blood and the number of third stage (L3) larvae developing in the mosquito vectors Aedes polynesiensis Marks and Culex quinquefasciatus Say (Diptera: Culicidae) after blood-feeding. Two types of curves are fitted to previously published data. Fitting a linearized power curve through the data allows for correction for measurement error in human Mf counts. Ignoring measurement error leads to overestimation of the strength of density dependence; the degree of overestimation depends on the accuracy of measurement of Mf density. For use in mathematical models of transmission of lymphatic filariasis, a hyperbolic saturating function is preferable. This curve explicitly estimates the Mf uptake and development at lowest Mf densities and the average maximum number of L3 that can develop in mosquitoes. This maximum was estimated at 23 and 4 for Ae. polynesiensis and Cx. quinquefasciatus, respectively.

Macrofilaricides and onchocerciasis control, mathematical modelling of the prospects for elimination.

BACKGROUND: In most endemic parts of the world, onchocerciasis (river blindness) control relies, or will soon rely, exclusively on mass treatment with the microfilaricide ivermectin. Worldwide eradication of the parasite by means of this drug is unlikely. Macrofilaricidal drugs are currently being developed for human use. METHODS: We used ONCHOSIM, a microsimulation mathematical model of the dynamics of onchocerciasis transmission, to explore the potentials of a hypothetical macrofilaricidal drug for the elimination of onchocerciasis under different epidemiological conditions, as characterized by previous intervention strategies, vectorial capacity and levels of coverage. RESULTS: With a high vector biting rate and poor coverage, a very effective macrofilaricide would appear to have a substantially higher potential for achieving elimination of the parasite than does ivermectin. CONCLUSIONS: Macrofilaricides have a substantially higher potential for achieving onchocerciasis elimination than ivermectin, but high coverage levels are still key. When these drugs become available, onchocerciasis elimination strategies should be reconsidered. In view of the impact of control efforts preceding the introduction of macrofilaricides on the success of elimination, it is important to sustain current control efforts.

Quality of sexually transmitted disease case management in Nairobi, Kenya: a comparison among different types of healthcare facilities.

BACKGROUND: In Nairobi, the prevalence for sexually transmitted diseases (STDs) among attenders at antenatal and family planning clinics is substantial, but knowledge about the quality of STD case management is scarce. GOAL: To assess quality of STD case management in Nairobi healthcare facilities. STUDY DESIGN: All the facilities in five sublocations were enumerated. In 142 facilities, 165 providers were interviewed, observed during 441 interactions with patients who had STDs, and visited by a simulated patient. RESULTS: For observations of patients with STDs, correct history-taking ranged from 60% to 92% among the various types of facilities, correct examination from 31% to 66%, and correct treatment from 30% to 75%. The percentage of correctness for all three aspects (World Health Organization prevention indicator 6) varied between 14% and 48%. Public clinics equipped for STD care performed best in all aspects, whereas treatment was poorest in pharmacies and private clinics. The providers trained in STD management performed better than those without training. CONCLUSIONS: Quality of STD case management was unsatisfactory except in public STD-equipped clinics. This indicates the need for improvement by interventions such as further training in syndromic management, improved supervision, and the introduction of prepackaged syndromic management kits.

Determinants of levels and changes of physical functioning in chronically ill persons: results from the GLOBE Study.

STUDY OBJECTIVE: Declines in physical functioning are a common result of chronic illness, but relatively little is known about factors not directly related to severity of disease that influence the occurrence of disability among chronically ill persons. The aim of this study was to assess the effect of a large number of potential determinants (sociodemographic factors, health related behaviour, structural living conditions, and psychosocial factors). DESIGN: Longitudinal study of levels and changes of physical functioning among persons suffering from four chronic diseases (asthma/chronic obstructive pulmonary disease (COPD), heart disease, diabetes, chronic low back pain). In 1991, persons suffering from one or more of these diseases were identified in a general population survey. Self reported disabilities, using a subset of the OECD disability indicator, were measured six times between 1991 and 1997. These data were analysed using generalised estimating equations, relating determinants measured in 1991 to disability between 1991 and 1997, and controlling for a number of potential confounders (age, gender, year of measurement, and type and severity of chronic disease). SETTING: Region of Eindhoven (south eastern Netherlands). PARTICIPANTS: 1784 persons with asthma/COPD, heart disease, diabetes mellitus and/or low back pain. MAIN RESULTS: In a "repeated prevalence" model, statistically significant (p<0.05) and strong associations were found between most of the determinants and the prevalence of disabilities. In a "longitudinal change" model, statistically significant (p<0.05) predictors of unfavourable changes in physical functioning were low income and excessive alcohol consumption, while we also found indications for effects of marital status, degree of urbanisation, smoking, and external locus of control. CONCLUSIONS: Other factors than characteristics of the underlying disease have an important influence on levels and changes of physical functioning among chronically ill persons. Reduction of the prevalence of disabilities in the population not only depends on medical interventions, but may also require social interventions, health education, and psychological interventions among chronically ill persons.

Internal validation of predictive models: efficiency of some procedures for logistic regression analysis.

The performance of a predictive model is overestimated when simply determined on the sample of subjects that was used to construct the model. Several internal validation methods are available that aim to provide a more accurate estimate of model performance in new subjects. We evaluated several variants of split-sample, cross-validation and bootstrapping methods with a logistic regression model that included eight predictors for 30-day mortality after an acute myocardial infarction. Random samples with a size between n = 572 and n = 9165 were drawn from a large data set (GUSTO-I; n = 40,830; 2851 deaths) to reflect modeling in data sets with between 5 and 80 events per variable. Independent performance was determined on the remaining subjects. Performance measures included discriminative ability, calibration and overall accuracy. We found that split-sample analyses gave overly pessimistic estimates of performance, with large variability. Cross-validation on 10% of the sample had low bias and low variability, but was not suitable for all performance measures. Internal validity could best be estimated with bootstrapping, which provided stable estimates with low bias. We conclude that split-sample validation is inefficient, and recommend bootstrapping for estimation of internal validity of a predictive logistic regression model.

A psychometric comparison of health-related quality of life measures in chronic liver disease.

Four generic [the Sickness Impact Profile (SIP-68), Short-Form Health Survey (SF-36), EuroQol instrument (EQ-5D), COOP/WONCA charts], two domain-specific health-related quality of life measures [the sexuality scale of the HIV Overview Problems Evaluating System (HOPES), Multi-dimensional Fatigue Index (MFI-20)], and a self-developed 12-item symptom index were compared in terms of feasibility, test-retest reliability, internal consistency reliability, construct validity, and known groups validity in patients with chronic liver disease. All instruments could be completed within 10 min and exhibited a good psychometric performance in patients with chronic liver disease. The SF-36 and the MFI-20 performed relatively best in terms of reliability, construct validity, and discriminative ability. The sexuality scale of the HOPES demonstrated a relatively poor performance, as the missing value rate was higher than 5%. Further research is needed into the sensitivity to important clinical changes of the instruments.

Neighborhood socioeconomic status and all-cause mortality.

This study sought to determine the contribution of neighborhood socioeconomic status to all-cause mortality and to explore its correlates. As part of the longitudinal "Gezondheid en LevensOmstandigheden Bevolking en omstreken" (GLOBE) study in the Netherlands, 8,506 randomly selected men and women aged 15-74 years from 86 neighborhoods in the city of Eindhoven reported on their socioeconomic status in the 1991 baseline survey. During the 6-year follow-up, 487 persons died. Neighborhood socioeconomic status was derived from individual reports on socioeconomic status. Its effect on mortality was stringently controlled for four individual-level socioeconomic indicators. Persons living in a neighborhood with a high percentage of unemployed/disabled or poor persons had a higher mortality risk than did those living in a neighborhood with a low percentage of unemployed/disabled or poor persons. This was independent of individual socioeconomic characteristics, including individual unemployment/disability or reports of severe financial problems. Educational and occupational neighborhood indicators were similarly, but less strongly, related to mortality. The prevalence of poor housing conditions, social disintegration, and unhealthy psychologic profiles and behaviors was higher in neighborhoods with a low socioeconomic status. Contextual effects of socioeconomic status may thus be due to one or more of these specific circumstances. The findings indicate potential public health benefits of modifying socioeconomic characteristics of areas.

Economic development and traffic accident mortality in the industrialized world, 1962-1990.

BACKGROUND: We examined the association between prosperity and traffic accident mortality in the industrialized world in a long-term perspective. METHODS: We calculated traffic accident mortality, traffic mobility and the fatal injury rate of 21 industrialized countries from 1962 until 1990. We used mortality and population data of the World Health Organization (WHO), and figures on motor vehicle ownership of the International Road Federation (IRF). We examined cross-sectional and longitudinal associations of these traffic-related variables with the prosperity level per country, derived from data of the Organization for Economic Cooperation and Development (OECD). RESULTS: We found a reversal from a positive relation between prosperity and traffic accident mortality in the 1960s to a negative association currently. At a certain level of prosperity, the growth rate of traffic mobility decelerates and the fatal injury rate continues to decline at a similar rate to earlier phases. CONCLUSIONS: In a long-term perspective, the relation between prosperity and traffic accident mortality appears to be non-linear: economic development first leads to a growing number of traffic-related deaths, but later becomes protective. Prosperity growth is not only associated with growing numbers of motor vehicles in the population, but also seems to stimulate adaptation mechanisms, such as improvements in the traffic infrastructure and trauma care.

Mammography requests in general practice during the introduction of nationwide breast cancer screening, 1988-1995.

Introducing an organised breast cancer screening programme for certain age groups in a population might induce opportunistic screening in adjacent (non-invited) age groups and influence health behaviour in the target population. We analysed the effect of the start of the Dutch national screening programme on the number of mammographies requested by 43-45 general practices for the age groups 30-39, 40-49, 50-69 and 70+ years, using logistic regression analysis. In all age groups an immediate increase was observed in the number of mammography requests after the start of the screening, which was largest and statistically significant in the target population of the screening programme (age 50-69 years). More than 2 years after the start of screening, the number of mammography requests in all age groups had decreased to the level before the start and in the age group 50-69 years the number of mammographies was significantly lower than before the screening started. The unexpected increase in mammographies after the start of the breast cancer screening programme might be related to registry problems or to the process of building up the screening programme. Eventually there was a decrease in the number of mammographies in the target population, probably an effect of the introduction of the national screening programme. Opportunistic screening was not clearly demonstrated in adjacent age groups.

Diurnal variation in lung function in subgroups from two Dutch populations: consequences for longitudinal analysis.

We studied circadian variation in FVC, FEV1, PEF, TLC, VC, and RV between 9:00 A.M. and 9:00 P.M. and analyzed how this variation affected estimated longitudinal change. Data from 876 adults were obtained in a longitudinal survey of samples from two Dutch areas. Subjects participated in four surveys held at 3-yr intervals between 1975 and 1985. FVC, FEV1, PEF, and VC increased from 9:00 A.M. until noon and decreased afterwards. TLC was constant over the day, whereas RV decreased from 9:00 A.M. to noon. Average variation in FVC, FEV1 and PEF, expressed as percentages of average level, was 4. 8% (200 ml), 2.8% (86 ml), and 3.1% (250 ml/s), respectively. These results are compatible with circadian changes in airway size. No differences in variability were found between men and women. Significantly larger changes between 9:00 A.M. and noon were found in young adults, smokers, and those with respiratory symptoms than in other subgroups. Adjustment for diurnal variation reduced, albeit slightly, residual standard deviations of estimated longitudinal declines. Average diurnal change was large relative to underlying longitudinal change. Its effect on longitudinal change within an individual can therefore be large depending on age, smoking habits, symptomatology, number of visits, time of measurement, and difference in time between measurements. However, when people are measured at random times during the day for at least three visits, or when measurements are made after 11:00 A.M., effects of diurnal variation in pulmonary function on estimated average longitudinal decline are minimal.