Smoking behavior among participants in the nurses' health study.

We analyzed smoking behavior of 91,651 married female nurses, aged 30-55 years in 1976. The prevalence of smoking was similar among all birth cohorts. The largest percentage increase in starting to smoke occurred between ages 15 and 25 years; by age 25, 50 per cent had started smoking. The cessation rate was lowest in earlier birth cohorts and among nurses starting to smoke at earlier ages. The cessation rate increased substantially between 1963-73 compared with the period 1948-58.     

Prospective study of relative weight, height, and risk of breast cancer

We examined relative weight and height in relation to subsequent breast cancer risk among 115,534 women 30 to 55 years of age and free from cancer in 1976. By 1984, six hundred fifty-eight premenopausal and 420 postmenopausal breast cancers were documented during 734,716 person-years. Among premenopausal women, risk of breast cancer decreased significantly with increasing relative weight (relative risk for the highest category was 0.6). A similar inverse association was seen for recalled relative weight at 18 years of age. Postmenopausal breast cancer was not associated with relative weight, either recent or at age 18. Height was not associated with breast cancer risk among premenopausal women and only weakly related among postmenopausal women. These data suggest that obesity among premenopausal and early postmenopausal women does not increase breast cancer risk substantially.     

Ultrasensitive analysis of the intestinal absorption and compartmentalization of aluminium in uraemic rats: a 26Al tracer study employing accelerator mass spectrometry

BACKGROUND: Developments in accelerator mass spectrometry (AMS) now permit the determination of femtogram amounts of 26Al in blood and in various tissues with good precision and free of external contamination. METHODS: In the present study we used trace quantities of 26Al to investigate the intestinal absorption and compartmentalization of aluminium in rats with renal failure (Nx, 5/6 nephrectomy) and in pair- fed controls (C). Single oral doses of 20 ng 26Al were administered to six animals in each group and, subsequently, 24-h post-load 26Al was analysed in serum, urine, bone, liver, and spleen by means of AMS. RESULTS: Serum concentrations of 26Al were significantly lower in uraemic rats compared to controls, whereas urinary excretion was comparable (Nx, 7.11 +/- 5.78 pg/day vs C, 9.46 +/- 6.10 pg/day), suggesting a higher fraction of ultrafiltrable serum 26Al in uraemia. The target tissues of cellular transferrin-mediated 26Al uptake, liver and spleen, tended to show a larger degree of aluminium accumulation in controls (0.26 +/- 0.31 pg/g vs Nx, 0.14 +/- 0.10 pg/g and 0.37 +/- 0.27 pg/g vs Nx, 0.25 +/- 0.27 pg/g respectively). In contrast, in bone, a site of extracellular aluminium deposition, 26Al concentrations were more elevated in uraemia (1.22 +/- 0.59 pg/g vs C: 0.68 +/- 0.30 pg/g). Estimated total 26Al accumulation in all measured target tissues was significantly higher in uraemic rats (28.15 +/- 9.90 pg vs C: 17.03 +/- 7.03 pg) and total recovery of 26Al from tissue and urine was 26.58 +/- 6.74 pg in controls and 35.75 +/- 7.03 pg in uraemic animals, suggesting a fractional absorption of 0.133% and 0.175% respectively. CONCLUSIONS: Our data suggest that fractional absorption from a dietary level dose of 26Al is about 0.13%. Compartmentalization occurs in transferrin-dependent target tissues such as liver and spleen; however, in quantitative terms extracellular deposition in bone is more important. Uraemia has a significant effect on the intestinal absorption and compartmentalization of aluminium. It enhances fractional absorption and increases subsequent extracellular deposition of aluminium in bone. However, at the same time uraemia does not increase transferrin-dependent cellular accumulation of aluminium in liver and spleen.      

Reproducibility and validity of self-reported menopausal status in a prospective cohort study

The reproducibility and validity of self-reported menopausal status were evaluated among the 121,700 female US registered nurses aged 30-55 years in 1976 who are participants in the Nurses' Health Study, a prospective cohort study of diseases in women. When questioned in 1978, 6,591 of the women who were premenopausal in 1976 reported that their menses had ceased and provided their age at menopause. Two years later, in 1980, 98.8 per cent of the 6,591 women again reported that they were postmenopausal and again gave the reasons for menopause (natural or surgical). Among those women who reported surgical menopause during the 1976-1978 follow-up interval, age at menopause was reported to within one year on both the 1978 and 1980 questionnaires by 95 per cent of women. Among those reporting natural menopause during the 1976-1978 period, 82 per cent of women reported their age at menopause to within one year on the two follow-up questionnaires. A random sample of 255 women reporting surgical menopause between 1982 and 1984 was identified and medical records were obtained for 200. For all but two women, there was complete agreement between self-report and medical record for details of hysterectomy and extent of ovarian surgery. The reproducibility of self-reported age at menopause was assessed among 31,405 women who were menopausal in 1976. Reported age at menopause on consecutive questionnaires showed increasing within-person variance with increasing duration since menopause.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of linoleic and oleic acids on blood pressure, blood viscosity, and erythrocyte cation transport

It has been proposed that dietary linoleic acid lowers blood pressure (BP) by being converted to arachidonic acid and prostanoids of the two-ene series. We tested the effects of linoleic acid on plasma arachidonic acid, blood pressure, blood viscosity, and RBC cation transport. Oleic acid, the major dietary monounsaturated fat and which is not a prostanoid precursor, was used as a control. Seventeen adults consumed 23 g/d of linoleic acid or oleic acid provided by genetic variants of safflower seed, each for 4 weeks in a double-blind crossover design. Linoleic and oleic acids were enriched significantly in the plasma cholesteryl esters, phospholipids and triglycerides during the respective periods of supplementation but there was no increase in arachidonate. Mean BP was 116.1/76.8 during ingestion of oleic and 113.6/74.6 during ingestion of linoleic acid (p = 0.09 systolic, p = 0.12 diastolic). The power of the study was over 75% for detecting a significant (p less than 0.05) effect of 4 mm Hg in systolic BP or diastolic BP. Whole blood and plasma viscosity, and RBC Li/Na countertransport, Na/K cotransport, and Na pump systems (Vmax) were unchanged during the protocol. Therefore, variations in dietary linoleic or oleic acids are unlikely to have major effects on BP or on several membrane-dependent erythrocyte functions related to hypertension.     

Risk of symptomatic gallstones in women with severe obesity.

Although obesity is a well-recognized risk factor for gallstones, the excess risks associated with higher levels of obesity and recent weight change are poorly quantified. We evaluated these issues in the Nurses' Health Study. Among 90,302 women aged 34-59 y at baseline followed from 1980 to 1988, 2122 cases of newly diagnosed symptomatic gallstones occurred during 607,104 person-years of follow-up. From 1980 to 1986, 488 cases of newly diagnosed unremoved gallstones were documented. We observed a striking monotonic increase in gallstone disease risk with obesity; women with a body mass index (BMI) greater than 45 kg/m2 had a sevenfold excess risk compared with those whose BMI was less than 24 kg/m2. Women with a BMI greater than 30 kg/m2 had a yearly gallstone incidence of greater than 1% and those with a BMI greater than or equal to 45 kg/m2 had a rate of approximately 2%/y. Recent weight loss was associated with a modestly increased risk after adjustment for BMI before weight loss. Current smoking was an independent risk factor; women smoking greater than or equal to 35 cigarettes/d had a relative risk of 1.5 (95% CI 1.2-1.9).     

Plasma C-peptide and cognitive performance in older men without diabetes.

BACKGROUND: Emerging evidence suggests that type 2 diabetes may be related to diminished cognition, but little data are available directly regarding the role of insulin levels. OBJECTIVE: The objective of this prospective cohort study was to examine the relation of insulin secretion to cognitive function among men without diabetes. SETTING: The study setting was the Physicians' Health Study-U.S. male physicians. PARTICIPANTS: Three hundred sixty-seven men who provided blood samples in 1982, when they had no lifetime history of diabetes and ranged in age from 47-65 years (mean age: 57 years). MEASUREMENTS: The authors assayed plasma C-peptide, reflecting insulin secretion, in the stored blood samples. Beginning in 2001, an average 18 years after blood collection, the authors administered telephone interviews, including tests of general cognition (Telephone Interview of Cognitive Status [TICS]), verbal memory, and category fluency. The authors used regression models to estimate mean differences in cognitive performance across levels of C-peptide controlling for a wide variety of potential confounding factors. RESULTS: On the TICS, men in the top tertile of C-peptide performed significantly worse than those in the bottom (multivariable-adjusted mean difference: -1.01 points, 95% confidence interval: -1.78 to -0.24); this apparent impact of C-peptide on cognition was equivalent to the cognitive differences the authors observed between men 6 years apart in age. Performance on the global score (combining results from all the individual tests) and verbal memory score (combining results from four tests of verbal memory) appeared lower among men in the highest C-peptide tertile, but results were not statistically significant. CONCLUSION: Higher midlife insulin secretion may be related to decreased later-life cognitive function, even among men without diabetes.