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Biomedical subjects

S M McKinlay

Publications and source records attributed to S M McKinlay.

At least 55 records · Page 3Linked to original sources
PubMed1986

Aging in a 'healthy' population.

A five-year project, building on an ongoing epidemiological study of menopause in 2500 women, will examine the aging process in middle-aged and older men, women, and couples in Massachusetts. While past research on aging has usually focused on disease and has drawn on a self-selecting, usually clinical population, our study will examine healthy individuals randomly selected from the general population. This approach should allow for increased inferential power of findings on how positive adjustment to the aging process occurs. The project is multi-disciplinary, combining physiological measurements (hormone levels, bone densities, etc.) with psychosocial data, and draws on previous experience with community-based methods of collecting physiological and psychological information in large health surveys.

Aged↗
PubMed1985

Statistical constraints on microvascular measurements using fluorescent erythrocytes.

We show that two separate estimators of microvessel hematocrit (H) using the same fluorescent cell technique are not equally precise. The precision of H (indicated by the coefficient of variation, CV) depends on in vivo labeled cell counts (m), the labeled fraction (p), and for time-averaged H estimates, the mean cell velocity (v). Thus, for length-dependent estimates of H, CV2(HL) = 1/E(m) + CV2(p) and for time-averaged H estimates, CV2(Ht) = 1/E(m) + CV2(p) + CV2(v). Because CV(p) can be made small arbitrarily and independently, the precision of H is principally dependent on the expected value of m. Practical sampling constraints and minimum sampling intervals are identified and used to define strategies to minimize CV(H). We show that Ht is preferable to HL because it is more precise and the useful in vivo sampling range of m and p is more flexible. In addition, Ht allows simultaneous determination of cell flux and mean cell velocity.

Erythrocytes↗
PubMed1985

Smoking and age at menopause in women.

Although women can expect to live one half of their adult lives beyond menopause, knowledge about this physiologic event and its various influences on subsequent health and quality of life remains incomplete. In Massachusetts we studied a population-based random sample of 7828 white women, aged 45 to 55 years (response rate, 77%). The median age at last menstruation for the sample is 51.4 +/- 0.19 (SE) years years, and we found no evidence of a secular trend towards a later age at menopause in the last 25 years. Current smokers reach menopause an average of 1.74 years earlier than nonsmokers (t = 3.78, p less than 0.01), but the quantity smoked has a negligible effect. Other potential correlates measured--education and marital status, number of children, and urban/rural residence--have little effect on the age at menopause. The results confirm earlier, more tentative findings from clinical populations.

Age Factors↗
PubMed1979

The influence of a premarital conception and various obstetric complications on subsequent prenatal health behaviour.

This paper is a companion to an earlier report on prenatal visiting patterns in Aberdeen, Scotland (McKinlay, 1970). It examines the following three main questions: (1) Is the emerging trend towards later maternity care among young nulliparae largely due to those who delay because of premarital conception? (2) If premarital conception is primarily responsible for this trend, is this pattern of visiting behaviour continued in subsequent pregnancies, and what variation is there in such behaviour--between, for example, different socioeconomic groups and age groups? (3) Does the presence of one or more obstetric complications associated with a first pregnancy or birth have an effect on subsequent prenatal health behaviour, and does this effect, if present, interact with, say, socioeconomic status, or the legal status of the first pregnancy? The paper concludes with a discussion of some policy implications of the findings.

Adult↗
PubMed1977

Pair-matching-a reappraisal of a popular technique.

Pair-matching is undoubtedly one of the most popular techniques for controlling variation in both medical and other investigations involving human populations. Given the obvious advantages of ease of implementation and comprehension, apparent efficiency and simplicity of analysis, this popularity is understandable. Despite this appeal, however, pair-matching frequently involves high cost (particularly in the loss of unmatchable units), cannot claim efficiency when appropriate comparisons of precision are made, and suffers some important limitations in the analysis which directly affect inference. The persistence of the technique in the face of these limitations is discussed with reference to the disjunction between theoretical models and practical research constraints. It is concluded that this design may not be the optimal choice in many, if not most, research situations.

Biometry↗
PubMedDate not supplied

Operational design and quality control in the CATCH multicenter Trial.

BACKGROUND: The Child and Adolescent Trial for Cardiovascular Health (CATCH) was the first multicenter school-based research study to employ the fundamentals of clinical trials including the standardized protocol and Manuals of Operation, a steering committee for study governance, a distributed data system, an extensive quality control system, and a Data and Safety Monitoring Board. METHOD: CATCH tested the effectiveness of changes in school lunches, physical education, smoking policy, curricula, and family activities. Ninety-six elementary schools in four states were randomized to intervention or control conditions. The baseline cohort comprised 5, 106 ethnically diverse third graders followed through fifth grade. RESULTS: The percentages of calories from fat and saturated fat were reduced significantly more in the intervention school lunches than among the controls. Significant increases in moderate to vigorous activity levels in existing physical education classes were made as well. Changes in self-reported dietary, physical activity, and psychosocial measures were significant. There were no significant differences in the physiological measures. Measurement error was generally low for all physiologic measures except skinfolds, indicating a high level of reliability. Across all sites, the coefficients of variation for lipids, height, and weight were less than 3%, whereas for skinfolds, they were considerably higher, ranging from 6 to 8%. Intraclass correlations for lipid studies were also uniformly high at 0.99. Interobserver agreement scores for SOFIT were greater than 90% for 9 of the 11 activities observed. Data entry error rates were low with less than five errors per 1,000 fields for all forms. CONCLUSIONS: The CATCH results provided more scientific evidence on the importance of schools in the population approach to health promotion. Many of the strategies used in this complex multicenter trial in the areas of design and analysis, measurement, training, data management, and quality control protocols might be appropriate for adoption in other studies.

Adolescent↗
PubMedDate not supplied

Issues in design, measurement, and analysis for menopause research.

Two broad classes of studies relating to menopause are reviewed: descriptive studies (cross-sectional or longitudinal); and comparative studies (observational or experimental). For descriptive studies the issues are: costs of sampling from a general population; measurement of last menstrual period (LMP) in the context of hormone therapy; unbiased symptom reporting in ethnically diverse populations; and in-home vs. clinic-based measurement. Comparative cohort studies of menopause-related therapies are somewhat more vulnerable to selection bias from medical care access than case-control studies with hospital or patient controls. Ideally, in clinical trials, no subjects should have previously used any of the trial therapies to ensure unbiased assessment of side effects and to maximize preservation of masking if a placebo is used. In terms of analysis, information (precision) depends on the proportion in the sample for whom LMP is defined, not the total number in the sample. The role of cigarette smoking as covariate in any analysis is of particular concern as it is the major determinant of the timing of LMP. These design and analysis issues, although identified from research to date, are still new. Some lack wide documentation and are thus not well understood. Others lack clear solutions.

Cohort Studies↗
PubMedDate not supplied

A longitudinal study of weight and the menopause transition: results from the Massachusetts Women's Health Study.

OBJECTIVE: Results of past studies of menopause and weight are inconsistent, in part because of problems in study design and analyses, such as retrospective assessment of age at menopause and failure to control for confounding factors. To address such shortcomings, we conducted multivariate analyses on longitudinal data from a large, community-based sample of initially pre- and perimenopausal women who were making the transition through menopause. DESIGN: Data were from the second phase of the Massachusetts Women's Health Study, a cohort of 418 women aged 50-60 years in 1986. We assessed the relationship between menopause transition and weight, after accounting for previous weight; age; and the behavioral factors of smoking, exercise, and annual ethanol consumption. Menopause status was defined in terms of months of amenorrhea. The association of hormone replacement therapy and weight also was examined. RESULTS: Menopause transition was not consistently associated with increased weight, and use of hormone replacement therapy was not significantly related to weight. Behavioral factors--particularly exercise and ethanol consumption--were more strongly related to weight than was menopause transition. CONCLUSIONS: These results are consistent with findings from other studies that suggest that the weight increases experienced by middle-aged women in the United States are not a result of the menopause transition.

Aging↗
PubMedDate not supplied

Can follicle-stimulating hormone be used to define menopausal status?

OBJECTIVE: To assess the ability of the level of follicle-stimulating hormone (FSH) to distinguish among premenopausal, perimenopausal, and postmenopausal women. METHODS: We examined cross-sectional and longitudinal data from the second phase of the Massachusetts Women's Health Study (1986 to 1995), a population-based cohort of 427 premenopausal and perimenopausal women identified from the first phase of the Massachusetts Women's Health Study (1981 to 1986). RESULTS: Boxplots of FSH levels throughout the menopausal transition displayed considerable overlap. Logistic regressions and their resulting receiver operating characteristic curves further demonstrated that, although FSH is a statistically significant predictor of menopausal status, no single value of FSH is expedient for distinguishing premenopausal from perimenopausal or perimenopausal from postmenopausal women. CONCLUSION: FSH alone is not an effective predictor of transition into the perimenopausal or postmenopausal period. Specifically, the frequently recommended FSH cutoff of 40 IU/L is inappropriate by itself for clinical determination of postmenopausal status.

Journal Article↗
PubMedDate not supplied

Performance characteristics of a blood cholesterol measuring instrument used in screening programs.

Four experiments were conducted to assess the precision and accuracy of the Boehringer Mannheim Diagnostics Reflotron, an instrument that is being adopted by many public health groups to conduct blood cholesterol screening programs. Our study is one of the first to evaluate and document the instrument's performance characteristics. Successive generations of reagent tabs supplied by the manufacturer were tested against a reference laboratory method standardized by the Centers for Disease Control. Three of the experiments also compared two or more Reflotrons to assess intermachine reliability. The Reflotron analyzer provided precise blood cholesterol measurements both in repeated tests and among instruments. The accuracy of the method varied across reagent lots, with an average negative bias of 21.05 milligrams per deciliter (mg per dl), decreasing steadily to a negative bias of 4.07 mg per dl. Reliability between and within analyzers was high. The data provide support for the use of the instrument in blood cholesterol screening efforts, yet signal the need for attention to quality control procedures, both by the manufacturer and operators, to ensure the validity and accuracy of the results.

Cholesterol↗
PubMedDate not supplied

The Massachusetts Women's Health Study: an epidemiologic investigation of the menopause.

This paper presents findings from the Massachusetts Women's Health Study (MWHS), one of the largest population-based studies of mid-aged women. A longitudinal study that followed a population-based cohort of women as they proceeded through menopause, the MWHS's goal was to describe their responses and to identify health-related, life-style, and other social factors that affect this transition. Findings indicate that natural menopause appears to have no major impact on health or health behavior. The majority of women do not seek additional help concerning menopause, and their attitudes toward it are, overwhelmingly, positive or neutral. Physicians treating mid-aged women must be careful not to confuse "menopausal" symptoms with indicators of underlying disease or conditions unrelated to menopause.

Attitude↗