Carpal tunnel syndrome: a nested case-control study of risk factors in women.

Risk factors for the development of carpal tunnel syndrome in women were studied by means of a nested case-control analysis of a prospective cohort study of the health effects of oral contraception in British women. A total of 1,264 women who had a diagnosis of carpal tunnel syndrome reported by their general practitioner between 1968 and 1993 were compared with 1,264 age-matched control women who did not have this diagnosis. The syndrome was associated in older women with some hormonal factors, notably past use of oral contraception (adjusted odds ratio in women aged 40 years and over = 1.38, 95 percent confidence interval: 1.08, 1.76) and more generally with obesity (adjusted odds ratio = 1.68, 95 percent confidence interval: 1.29, 2.18). However, the strongest link was with a previous history of another musculoskeletal complaint for which consultation had been sought (adjusted odds ratio = 1.98, 95 percent confidence interval: 1.61, 2.42). Previous findings of a higher risk in women with diabetes and myxoedema were confirmed, but these contribute only a small proportion of all cases in women. There was no link with psychologic problems or nonmusculoskeletal pain complaints. The previously described increased incidence of carpal tunnel syndrome in women may be partly due to hormonal factors, but is also related to an underlying propensity to musculoskeletal problems and their higher overall frequency in women.

Effects of changes in smoking status on risk estimates for myocardial infarction among women recruited for the Royal College of General Practitioners' Oral Contraception Study in the UK.

STUDY OBJECTIVE: To determine whether changes in smoking status among women recruited for the Royal College of General Practitioners' Oral Contraception Study affected previous risk estimates for myocardial infarction. DESIGN: (1) Postal survey between November 1994 and July 1995 of women still under general practitioner observation. Validation of the smoking information supplied by the women on the questionnaire by comparison with that reported by the general practitioner at recruitment to the main study. (2) Nested case-control study of 103 cases of myocardial infarction, matched with 309 controls, to see if different risk estimates were obtained when smoking status at recruitment or smoking status at time of event were used in the analysis. SETTING: 650 general practices throughout the United Kingdom. PARTICIPANTS: 10,073 women who responded to the questionnaire (85.4% of 11,797 sent out). MAIN RESULTS: There was good agreement between smoking information recorded by the general practitioner at recruitment and that supplied retrospectively by respondents to the questionnaire. The risk estimates for myocardial infarction associated with use of combined oral contraceptives (COCs) were almost identical irrespective of whether smoking status at recruitment or at time of event was used for the statistical adjustment. This was because few women stopped smoking while also using COCs. In fact, fewer regular smokers who have ever used COCs reported stopping smoking than never users. The risk estimates for myocardial infarction associated with smoking were smaller when smoking habits at recruitment was used than when smoking habits at time of event was used. CONCLUSIONS: Previous results from the Oral Contraception Study regarding the effects of COCs are unlikely to have been biased by changes in the smoking habits of the cohort, but the effects of smoking have probably been underestimated. There is still a need for effective health education regarding the risks associated with smoking, particularly among users of COCs.

Prevalence and characteristics associated with use of hormone replacement therapy in Britain.

OBJECTIVE: To describe trends in the prevalence of hormone replacement therapy (HRT) use among women living in Britain between 1981 and 1990, and to determine whether women who receive HRT are different from those who do not. DESIGN: Population-based, prospective, observational study. SETTING: Fourteen hundred general practices throughout the United Kingdom contributing data to the Oral Contraception Study of the Royal College of General Practitioners (RCGP). POPULATION: Prevalence of use: women still under general practitioner observation in the Oral Contraception Study at the end of December 1981 (n = 19,949), 1984 (n = 18,037), 1987 (n = 16,063), 1990 (n = 13,379). Characteristics of users: 3806 HRT users and 3806 never-users matched for age, hysterectomy status and duration of observation in the Oral Contraception Study. MAIN OUTCOME MEASURE: Ever-use of hormone replacement therapy. RESULTS: Between 1981 and 1990 there was a threefold increase in HRT use among women both among those who had and those who had not had a hysterectomy. Increasing trends were apparent in all age groups. By December 1990, 19% of all women (36% of those who had had a hysterectomy and 16% of those who had not had a hysterectomy) had ever used HRT; 9% were classified as current users. Forty-one percent of women using HRT who had had a hysterectomy received combined (oestrogen and progestogen) preparations; 31% of those who had not had a hysterectomy received at least one prescription for unopposed oestrogen. Among those who had had a hysterectomy, HRT was more likely to be prescribed in women with a history of smoking, nonpsychotic psychiatric illness, hot flushes, other menopausal symptoms, oophorectomy, migraine or headache. Women with breast cancer were less likely to receive HRT. In women who had not had a hysterectomy, smoking, nonpsychotic psychiatric illness, hot flushes, other menopausal symptoms, migraine, headache and previous use of oral contraceptives increased the chances of HRT being used; a history of breast cancer, ischaemic heart disease or diabetes mellitus reduced the chances. Weaker associations of reduced risk were also found for hypertension and lower social class. The influence of hot flushes and other menopausal symptoms appeared to be stronger in women who used HRT before the age of 50, than in older women. CONCLUSIONS: HRT use increased dramatically within the cohort during the nine year period. HRT users are different from nonusers in a number of ways which could have opposing effects on a woman's risk of cardiovascular disease.

Animal models for osteoarthritis--ensuring experimental validity.

Confounding factors, bias factors and hidden variables affect the design of experiments involving animal models. In a frequently used dog model for osteoarthritis these can arise, for example, because of the influence of age, sex and breed of dog. Controls are required to investigate the progression of osteoarthritis even in experiments forming time series. However, there are no true controls in animal models for joint degeneration. Analysis of data collected from experiments involving animal models depends on the number of factors being varied. The number of animals influences the level of confidence associated with a result. Ignoring statistics can invalidate conclusions drawn from the experiments. Statistical considerations are also important in the presentation of results.

Non-linear statistical technique applied to data from baboon articular cartilage.

Pattern recognition software was developed and applied together with statistical techniques to articular cartilage data from the knee joint of the baboon. The standard statistical method used for comparison was ANOVA which indicates linear discrimination. In addition a Karhunen-Loève expansion was performed to reduce the dimensionality of the data and provide independent uncorrelated variables. Nearest neighbour analysis, a non-linear method, when combined with bionomial probabilities gave discrimination that was not obtained by ANOVA. Use of pattern recognition and related techniques can improve and extend the analysis of biological data to include non-linear discrimination and classification.