***TASK*** the task is to summarize an input biomedical literature in six sentences 
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    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: BACKGROUND Assortative mating is the nonr and om mating of individuals with respect to phenotype and cultural factors . Previous studies of assortative mating for obesity have indicated that it may have contributed to the obesity epidemic . However , those studies all used body mass index or skinfold thicknesses to measure obesity and did not always account for potential confounding factors . OBJECTIVE We aim ed to assess the level of assortative mating for obesity by using dual-energy X-ray absorptiometry to characterize body composition . DESIGN This was a cross-sectional study of 42 couples . RESULTS Raw spousal correlations showed assortative mating for age , weight , body mass index , lean mass , and fat mass . Removing the effect of age on fat mass strengthened the spousal correlation ( r = 0.405 ) . Social homogamy did not appear to be important , because in this sample there was no significant effect of area of origin on age-corrected fat and lean tissue masses for either sex . Regional body-composition analysis showed that subjects with disproportionately large arms ( both fat and lean ) assortatively mated with partners with the same trait . However , both men and women with high lean tissue in their arms assortatively mated with partners that had a disproportionately low fat content in their legs . CONCLUSIONS These data confirm that assortative mating for obesity exists when dual-energy X-ray absorptiometry is used to evaluate adiposity . We hypothesize that assortative mating may have contributed to the obesity epidemic because the time course of obesity development has shifted progressively earlier , allowing singles in their late teens and early twenties to more easily distinguish partners with obese and lean phenotypes The YMCA ’s Diabetes Prevention Program gives you the skills you need and the support you deserve to make lasting healthy lifestyle changes . WHAT IS PREDIABETES ? Prediabetes occurs when blood sugar levels are higher than normal but not high enough for a type 2 diabetes diagnosis . Risk for developing type 2 diabetes may be reduced or eliminated by weight loss , healthier eating and increased physical activity Prevention of type 2 diabetes by intensive lifestyle intervention design ed to achieve and maintain ideal body weight was assessed in subjects with impaired glucose tolerance ( IGT ) . Male subjects with IGT recruited from health-screening examinees were r and omly assigned in a 4:1 ratio to a st and ard intervention group ( control group ) and intensive intervention group ( intervention group ) . The final numbers of subjects were 356 and 102 , respectively . The subjects in the control group and in the intervention group were advised to maintain body mass index ( BMI ) of < 24.0 kg/m2 and of < 22.0 kg/m2 , respectively , by diet and exercise . In the intervention group , detailed instructions on lifestyle were repeated every 3 - 4 months during hospital visits . Diabetes was judged to have developed when two or more consecutive fasting plasma glucose ( FPG ) values exceeded 140 mg/dl . A 100 g oral glucose tolerance test was performed every 6 months to detect improvement of glucose tolerance . The subjects were seen in an ordinary outpatient clinic . The cumulative 4-year incidence of diabetes was 9.3 % in the control group , versus 3.0 % in the intervention group , and the reduction in risk of diabetes was 67.4 % ( P < 0.001 ) . Body weight decreased by 0.39 kg in the control group and by 2.18 kg in the intervention group ( P < 0.001 ) . The control group was subclassified according to increase and decrease in body weight . The incidence of diabetes was positively correlated with the changes in body weight , and the improvement in glucose tolerance was negatively correlated . Subjects with higher FPG at baseline developed diabetes at a higher rate than those with lower FPG . Higher 2h plasma glucose values and higher BMI values at baseline were also associated with a higher incidence of diabetes , but the differences were not significant . Subjects with a low insulinogenic index ( DeltaIRI/DeltaPG 30 min after an oral glucose load ) developed diabetes at a significantly higher rate than those with a normal insulinogenic index . Comparison of the BMI data and incidence of diabetes in five diabetes prevention studies by lifestyle intervention revealed a linear correlation between the incidence of diabetes and the BMI values , with the exception of the DaQing Study . However , the slope of the reduction in incidence of diabetes in the intensive intervention groups was steeper than expected simply on the basis of the reduction of BMI , suggesting that the effect of lifestyle intervention can not be solely ascribed to the body weight reduction . We conclude that lifestyle intervention aim ed at achieving ideal body weight in men with IGT  is effective and can be conducted in an outpatient clinic setting This study of 220 wives of participants from four of the 22 clinics in the Multiple Risk Factor Intervention Trial ( MRFIT ) addresses the question of whether spouses of men exposed to a continuous coronary heart disease ( CHD ) risk-factor intervention program ( SI group )  make changes in their own risk status compared to wives of men who did not receive the intervention program ( UC group ) .  Total serum cholesterol and low-density lipopro-tein ( LDL ) cholesterol were significantly lower for the SI wives . These differences were found for both hypertensive and normotensive wives , although the magnitudes were much greater for the hypertensive wives . There were also significant differences between the two groups of wives in the food-record rating and in dietary-knowledge scores , indicating that the probable mechanism for the beneficial effect of the intervention with respect to cholesterol levels was the change in the family diet . Although not statistically significant , differences indicating a lower risk for SI wives were found for diastolic blood pressure . There was also a greater mean reduction in cigarettes per day for SI wives who smoked BACKGROUND In the 2.8 years of the Diabetes Prevention Program ( DPP ) r and omised clinical trial ,  diabetes incidence  in high-risk adults was reduced by 58 % with intensive lifestyle intervention and by 31 % with metformin , compared with placebo . We investigated the persistence of these effects in the long term . METHODS All active DPP participants were eligible for continued follow-up . 2766 of 3150 ( 88 % ) enrolled for a median additional follow-up of 5.7 years ( IQR 5.5 - 5.8 ) . 910 participants were from the lifestyle , 924 from the metformin , and 932 were from the original placebo groups .  On the basis of the benefits from the intensive lifestyle intervention in the DPP , all three groups were offered group-implemented lifestyle intervention . Metformin treatment was continued in the original metformin group ( 850 mg twice daily as tolerated ) , with participants unmasked to assignment , and the original lifestyle intervention group was offered additional lifestyle support . The primary outcome was development of diabetes according to American Diabetes Association criteria . Analysis was by intention-to-treat . This study is registered with Clinical Trials.gov , number NCT00038727 . FINDINGS During the 10.0-year ( IQR 9.0 - 10.5 ) follow-up since r and omisation to DPP , the original lifestyle group lost , then partly regained weight . The modest weight loss with metformin was maintained . Diabetes incidence rates during the DPP were 4.8 cases per 100 person-years ( 95 % CI 4.1 - 5.7 ) in the intensive lifestyle intervention group , 7.8 ( 6.8 - 8.8 ) in the metformin group , and 11.0 ( 9.8 - 12.3 ) in the placebo group . Diabetes incidence rates in this follow-up study were similar between treatment groups : 5.9 per 100 person-years ( 5.1 - 6.8 ) for lifestyle , 4.9 ( 4.2 - 5.7 ) for metformin , and 5.6 ( 4.8 - 6.5 ) for placebo . Diabetes incidence in the 10 years since DPP r and omisation was reduced by 34 % ( 24 - 42 ) in the lifestyle group and 18 % ( 7 - 28 ) in the metformin group compared with placebo . INTERPRETATION During follow-up after DPP , incidences in the former placebo and metformin groups fell to equal those in the former lifestyle group , but the cumulative incidence of diabetes remained lowest in the lifestyle group . Prevention or delay of diabetes with lifestyle intervention or metformin can persist for at least 10 years . FUNDING National Institute of Diabetes and Digestive and Kidney Diseases ( NIDDK ) A dietary intervention delivered to one family member with a beneficial impact on other members could provide a cost-effective approach to public health dietary intervention programs . The Women 's Health Trial ( WHT ) was a study in which women were r and omized to be trained in adopting a low-fat diet or to continue their normal diet . The intervention women consumed 21 % of total calories from fat versus 38 % for control women at six months postr and omization . Husb and s of women in the Seattle Clinical Center of the WHT were surveyed between 1985 and 1988 to determine whether and to what extent the husb and s ' diets changed at six months . Ninety-one intervention men and 162 control men , 79 % of those eligible , participated . Intervention men reported an average weight loss of 2.4 pounds , compared to an average 0.7-lb loss among controls ( P = .03 ) . Based on self-reported change of specific foods , we found that intervention men more often reduced butter , margarine , eggs , and red meat over the six months than did control men ( P less than .001 ) . Based on nutrient consumption estimated by a food frequency question naire , intervention husb and s consumed 34 % of total calories from fat versus 36 % for controls ( P = 0.04 ) . The number of meals shared with wives per week modified the effect of the intervention : among the intervention group , for every three meals shared , an accompanying one percentage point reduction in percentage of calories from fat occurred in the husb and 's diet . Thus , we suggest that dietary intervention programs attended by one spouse appear to exert a small beneficial effect on the other spouse OBJECTIVE Health administrative data are frequently used for diabetes surveillance , but validation studies are limited , and undiagnosed diabetes has not been considered in previous studies . We compared the test properties of an administrative definition with self-reported diabetes and estimated prevalence of undiagnosed diabetes by measuring glucose levels in mailed-in capillary blood sample s. RESEARCH DESIGN AND METHODS A stratified r and om sample of 6,247 individuals ( Quebec province ) was surveyed by telephone and asked to mail in fasting blood sample s on filter paper to a central laboratory . An administrative definition was applied ( two physician cl aims or one hospitalization for diabetes within a 2-year period ) and compared with self-reported diabetes alone and with self-reported diabetes or elevated blood glucose level ( ≥7 mmol/L ) . Population -level prevalence was estimated with the use of the administrative definition corrected for its sensitivity and specificity . RESULTS Compared with self-reported diabetes , sensitivity and specificity were 84.3 % ( 95 % CI 79.3–88.5 % ) and 97.9 % ( 97.4–98.4 % ) , respectively . Compared with diabetes by self-report and /or glucose testing , sensitivity was lower at 58.2 % ( 52.2–64.6 % ) , whereas specificity was similar at 98.7 % ( 98.0–99.3 % ) . Adjusted for sampling weights , population -level prevalence of physician-diagnosed diabetes was 7.2 % ( 6.3–8.0 % ) . Prevalence of total diabetes ( physician-diagnosed and undiagnosed ) was 13.4 % ( 11.7–15.0 % ) , indicating that ∼40 % of diabetes cases are undiagnosed . CONCLUSIONS A substantial proportion of diabetes cases are missed by surveillance methods that use health administrative data bases . This finding is concerning because individuals with undiagnosed diabetes are likely to have a delay in treatment and , thus , a higher risk for diabetes-related complications In Mendelian r and omization ( MR ) studies , where genetic variants are used as proxy measures for an exposure trait of interest , obtaining adequate statistical power is frequently a concern due to the small amount of variation in a phenotypic trait that is typically explained by genetic variants . A range of power estimates based on simulations and specific parameters for two-stage least squares ( 2SLS ) MR analyses based on continuous variables has previously been published . However there are presently no specific equations or software tools one can implement for calculating power of a given MR study . Using asymptotic theory , we show that in the case of continuous variables and a single instrument , for example a single-nucleotide polymorphism ( SNP ) or multiple SNP predictor , statistical power for a fixed sample size is a function of two parameters : the proportion of variation in the exposure variable explained by the genetic predictor and the true causal association between the exposure and outcome variable . We demonstrate that power for 2SLS MR can be derived using the non- central ity parameter ( NCP ) of the statistical test that is employed to test whether the 2SLS regression coefficient is zero . We show that the previously published power estimates from simulations can be represented theoretically using this NCP-based approach , with similar estimates observed when the simulation-based estimates are compared with our NCP-based approach . General equations for calculating statistical power for 2S 
    Output:
    
Conclusions Our pooled estimate suggests that a spousal history of diabetes is associated with a 26 % diabetes risk increase .