September 7, 2009 United States Death rates are at a record low and life expectancy is at a record high, according to the latest figures from the Centers for Disease Control and Prevention.
Preliminary data for 2007, released on Aug. 19, show that death rates have decreased to 760.3 per 100,000 from 776.5 in 2006, and a baby born in 2007 can expect to live 77.9 years, compared with 77.7 for one born in 2006.
Age-adjusted death rates decreased significantly for 8 of the 15 leading causes of death: heart disease, cancer, cerebrovascular disease, accidents, diabetes, influenza, high blood pressure and assaults.
The decreases in death rate held across all races and ethnicities, with black males showing the largest decrease — more than 4 percent. The drop occurred in all age groups except infants under 1 year old, where rates were unchanged.
Kenneth D. Kochanek, a co-author of the report and a statistician with the National Center for Health Statistics, said the findings were welcome.
“We want all leading causes of death to go down and life expectancy to go up,” Mr. Kochanek said. “That’s good news, but it doesn’t make the front page of the paper because it’s nothing spectacular.”
August 18, 2009 — The Dietary Approaches to Stop Hypertension (DASH) diet may help protect against kidney stones, according to the results of a prospective study reported online August 13 in the Journal of the American Society of Nephrology.
“Despite previously observed associations between individual dietary factors and kidney stone risk, relatively few studies have examined the impact of overall diet or dietary patterns on risk,” write Eric N. Taylor, MD, from Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, and colleagues.
“The [DASH] diet, which is high in fruits and vegetables, moderate in low-fat dairy products, and low in animal protein represents a novel potential means of kidney stone prevention. The consumption of fruits and vegetables increases urinary citrate, an important inhibitor of calcium stone formation, and a diet with normal to high calcium content but low in animal protein and sodium decreases the risk of calcium oxalate stone recurrence by 51%,” the researchers state.
The investigators studied the association between a DASH-style diet and incident kidney stones in the Health Professionals Follow-up Study (n = 45,821 men; 18 years of follow-up), Nurses’ Health Study I (n = 94,108 older women; 18 years of follow-up), and Nurses’ Health Study II (n = 101,837 younger women; 14 years of follow-up).
To determine degree of compliance with the DASH-style diet, the investigators constructed a DASH score based on 8 components: high consumption of fruits, vegetables, nuts and legumes, low-fat dairy products, and whole grains, and low consumption of sodium, sweetened beverages, and red and processed meats. Cox hazards regression allowed adjustment for age, body mass index (BMI), fluid intake, and other clinical factors.
During a combined follow-up of 50 years, there were 5645 incident kidney stones. Intakes of calcium, potassium, magnesium, oxalate, and vitamin C were higher in participants with higher DASH scores, and sodium intakes were lower.
For participants in the highest vs the lowest DASH score quintile, the multivariate relative risks for kidney stones were
0.55 (95% confidence interval [CI], 0.46 – 0.65) for men,
0.58 (95% CI, 0.49 – 0.68) for older women, and
0.60 (95% CI, 0.52 – 0.70) for younger women.
The observed reductions in kidney stone risk were independent of age, BMI, fluid intake, and other factors. Even in participants with lower calcium intake, higher DASH scores predicted lower risk for kidney stones. The findings were unaffected by excluding participants with hypertension.
“Consumption of a DASH-style diet is associated with a marked decrease in kidney stone risk,” the study authors write. “In contrast to our previous studies of individual dietary factors and kidney stone risk in these populations, the impact of a DASH-style diet was similar in men and women, in older and younger individuals, and in participants with both low and high BMI.”
Limitations of this study include lack of data on stone composition reports from all stone formers, failure to examine the effect of DASH score on 24-hour urine calcium, poor measurement of sodium intake, and limited generalizability.
“Although we think it reasonable for calcium oxalate stone formers with high levels of urinary oxalate to avoid intake of some individual foods very high in oxalate (such as spinach and almonds), our data do not support the common practice of dietary oxalate restriction in calcium stone formers, particularly if such advice results in lower intake of fruits, vegetables, and whole grains. Because of the adverse side effect profile of many current medical therapies for nephrolithiasis, a randomized trial is needed to determine the efficacy of a DASH-style diet compared with medical intervention for the secondary prevention of calcium oxalate kidney stones.”
The National Institutes of Health supported this study. The study authors have disclosed no relevant financial relationships.
J Am Soc Nephrol. Published online August 13, 2009.
Clinical Context
The DASH diet may improve the risk for nephrolithiasis through a variety of mechanisms. The increased consumption of fruits and vegetables in DASH can increase urinary citrate, which is a strong inhibitor of calcium stones. At least moderate calcium intake from low-fat dairy products can also reduce the risk for stones, and the low levels of animal protein and salt intake in DASH can reduce the risk for calcium stones. At the same time, some vegetables and legumes can increase urinary oxalate levels, which could promote a higher risk for stones.
The current study uses large patient cohorts from the Nurses’ Health Study and Physicians’ Health Study to determine the effect of the DASH diet on the risk for kidney stones.
Study Highlights
- The Nurses’ Health Study I enrolled 121,701 women between the ages of 30 and 55 years in 1976, and the Nurses’ Health Study II evaluated 116,671 women between the ages of 25 and 42 years in 1989. The Physicians’ Health Study enrolled 51,529 men between the ages of 40 and 75 years in 1986.
- Researchers used a semiquantitative food frequency questionnaire to measure adherence to the DASH diet. Previous validity studies of these questionnaires confirmed that they were representative of subjects’ actual diets.
- Specifically, researchers focused on the following elements of the DASH diet: high consumption of fruits, vegetables, nuts, low-fat dairy products, whole grains, and legumes and low consumption of sodium, sweetened beverages, red meat, and processed meats. Researchers assigned participants into quintiles on the basis of their adherence to the DASH diet.
- The main study outcome was the interaction between adherence to the DASH diet and incident kidney stones. Diagnoses of kidney stones were recorded by patient self-report. The main result was adjusted to account for participant age, BMI, total energy intake, fluid intake, caffeine use, alcohol use, and a history of hypertension or diabetes.
- During a combined 50 years of follow-up, there were 1717 incident kidney stones recorded in the Physicians’ Health Study cohort (men). There were 1675 and 2253 incident stones in the Nurses’ Health Study I (older women) and II (younger women) cohorts, respectively.
- Participants in the highest quintile of DASH consumption had a lower BMI and prevalence of diabetes compared with lower quintiles.
- Participants in the highest quintiles of DASH consumption had lower adjusted relative risks for kidney stones compared with participants in the lowest quintile. This was true among men (RR, 0.55), older women (RR, 0.58), and younger women (RR, 0.60).
- The exclusion of participants with diabetes or hypertension at baseline did not alter the study’s main conclusion. The DASH diet’s efficacy in reducing the risk for kidney stones did not vary by age or BMI, and the DASH diet was also effective among participants with a low overall calcium intake.
Clinical Implications
- Components of the DASH diet that could promote a lower risk for kidney stone formation include higher consumption of fruits and vegetables, at least moderate intake of low-fat dairy products, and reduced consumption of salt and animal protein.
- In the current study, adherence to the DASH diet was associated with a reduced risk for kidney stone formation among men, older women, and younger women. The DASH diet’s efficacy in reducing the risk for kidney stones did not vary by age or BMI.