Factors associated with refusal to provide a buccal cell sample in the Agricultural Health Study.

Epidemiological studies are increasingly collecting buccal cells and other sources of DNA for genetic analysis. However, high refusal rates raise concerns about possible selection bias. This study examines the subject characteristics associated with refusal or failure to provide a buccal cell sample. Subjects were male farmers in the Agricultural Health Study, which is being conducted in Iowa and North Carolina. As part of a 5-year follow-up, cohort members were contacted by telephone and asked to participate in a telephone interview and to consent to providing a buccal cell sample using a kit that was mailed to them. Demographic, lifestyle, disease, and occupational characteristics were compared between consenters who returned a sample ("compliers"), nonconsenters ("refusers"), and consenters who failed to return a sample ("noncompliers"). Compliers (n = 8794), refusers (n = 3178), and noncompliers (n = 3008) were quite similar, although compliers tended to be slightly older. Although some significant differences between these groups were observed, the magnitude of these differences was generally small, usually no more than a few percentage points. In conclusion, this study found little difference between male farmers who agreed to provide buccal cell samples versus those who either refused to provide a sample or who agreed but failed to return the sample. Observed differences were typically small and would be unlikely to compromise etiologic associations identified in such a prospective study. In short, there appears to be little selection bias in the Agricultural Health Study buccal cell collection process, further supporting the use of such mailed collection kits in epidemiological research.

Predictors of postoperative movement and resting pain following total knee replacement.

This study determined preoperative predictors of movement and resting pain following total knee replacement (TKR). We hypothesized that younger patients with higher preoperative pain intensity, pain sensitivity, trait anxiety, pain catastrophizing, and depression would be more likely to experience higher postoperative movement pain than older patients with lower scores on these variables prior to surgery, and that predictors would be similar for resting pain. Demographics, analgesic intake, anxiety, depression, pain catastrophizing, resting pain, movement pain (ie, during active knee range of motion), and quantitative sensory tests were performed preoperatively on 215 participants scheduled for a unilateral TKR. On postoperative day 2, analgesic intake, resting pain, and movement pain were again assessed. Significant predictors of moderate or severe movement pain were higher preoperative movement pain, von Frey pain intensity, and heat pain threshold. People with severe movement pain preoperatively were 20 times more likely to have severe movement pain postoperatively. When the influence of preoperative movement pain was removed, depression became a predictor. Significant predictors of moderate to severe resting pain were higher preoperative resting pain, depression, and younger age. These results suggest that patients with higher preoperative pain and depression are more likely to have higher pain following TKR, and younger patients may have higher resting pain. Cutaneous pain sensitivity predicted movement pain but not resting pain, suggesting that mechanisms underlying movement pain are different from resting pain. Aggressive management of preoperative pain, pain sensitivity, and depression prior to surgery may facilitate postoperative recovery.

Comparison of farmers in the agricultural health study to the 1992 and the 1997 censuses of agriculture.

CONTEXT: The Agricultural Health Study (AHS) is a large, prospective cohort study in the states of Iowa and North Carolina that has been developed to better understand how pesticides and other agricultural exposures relate to the occurrence of cancer and other diseases. PURPOSE: This report compares the characteristics of AHS farmers to the Census of Agriculture to evaluate the generalizability of AHS findings. METHODS: We restricted the AHS to private pesticide applicators who enrolled in Iowa (n = 31,065) and in North Carolina (n = 17,239) between 1993 and 1997, and who identified themselves as living or working on a farm. We compared their self-reported data with data from the 1992 and 1997 Censuses of Agriculture. FINDINGS: AHS farmers in Iowa are younger; live or work on larger farms; more frequently apply herbicides, insecticides, and fungicides; and are more likely to raise beef cattle and swine, and grow corn, soybeans, hay, and oats. AHS farmers in North Carolina are also younger, live or work on larger farms, more frequently reported growing crops commonly seen in the state, and are more frequent pesticide users. However, animals raised are similar to those in the North Carolina Census of Agriculture. CONCLUSIONS: AHS farmers likely represent the higher end of pesticide usage in both states in part because AHS farmers have larger farms. Since the health effects of pesticides are best ascertained among pesticide users with the greatest exposure, the AHS cohort should prove to be a valuable resource for health effects research.

Work, leisure-time physical activity, and risk of preeclampsia and gestational hypertension.

Few studies of preeclampsia have assessed physical activity level, yet recent evidence suggests that the pathologic mechanisms in preeclampsia are similar to those in cardiovascular disease, for which physical activity is shown to be protective. The authors assessed the independent and combined effects of work and regular leisure-time physical activity (LTPA) during early pregnancy on risk of de novo preeclampsia (n = 44) and gestational hypertension (n = 172) among women recruited from 13 obstetric practices in the New Haven, Connecticut, area between 1988 and 1991. Control subjects were normotensive throughout pregnancy (n = 2,422). Information on time at work spent sitting, standing, and walking and on LTPA before and during pregnancy was collected via face-to-face interviews. Logistic regression analyses suggested that women who engaged in any regular LTPA regardless of caloric expenditure (adjusted odds ratio (aOR) = 0.66, 95% confidence interval (CI): 0.35, 1.22), were unemployed (aOR = 0.64, 95% CI: 0.21, 2.00), or had nonsedentary jobs (aOR = 0.71, 95% CI: 0.37, 1.36) were at decreased risk of preeclampsia. Analyses of gestational hypertension showed no indication of a protective effect of workplace activity, LTPA, or unemployment. Consistent with other studies, these data suggest that regular physical activity during pregnancy may reduce preeclampsia risk.

Optimizing buccal cell DNA yields in mothers and infants for human leukocyte antigen genotyping.

Buccal cells provide a convenient source of DNA for epidemiologic studies. Mouthwash rinses yield a higher quality and quantity of DNA than cytobrushes but are not practical for collection from infants. Although cytobrushes yield sufficient DNA for most genotyping analyses, human leukocyte antigen (HLA) analysis can require 1,000-fold more DNA. In Iowa City, Iowa, in 2002, the authors tested two cytobrush collection methods to optimize total DNA yield and purity for HLA genotyping in mothers and infants: 1) brushing the left and right inner cheeks (standard method) and 2) brushing the upper and lower "gutters", that is, the space between the gums and the inner lips/cheeks along the front and sides of the mouth (test method). Storage and mailing experiments were performed to define conditions for optimizing DNA yield and purity. Mothers' gutter samples yielded significantly higher total amounts of DNA (mean yield = 15.0 micro g/two brushes) than cheek samples (mean yield = 7.6 micro g/two brushes) (paired t test: p < 0.001), while DNA yields from cheek and gutter collections from infants were equivalent. Cytobrushes stored and/or mailed in paper envelopes yielded significantly more and higher-purity DNA than brushes in plastic bags or tubes. Cytobrush sampling of the mouth's gutter areas can enhance DNA yield in mothers but not in young infants. DNA yields can be further optimized by controlling mailing and storage conditions.