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Department of Nutrition, Dietetics and Food Science, Brigham Young University, Provo, Utah
Address reprint requests to: Kay B. Franz, PhD, RD, FACN, Department of Nutrition, Dietetics and Food Science, Brigham Young University, Provo, UT 84602. E-mail: kay_franz{at}byu.edu
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ABSTRACT |
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Methods: These geographical variations, by state, were compared to the tertiles of the Z-score (Z-climate) obtained from the mean annual temperature and precipitation, by state, and to the tertiles of the Z-score (Z-environment) obtained from six environmental factors, by state, in monovariant analyses of variance.
Results: Both Z-scores were significantly related to male heart deaths (Z-climate: p = 0.000009; Z-environment: p = 0.000043) with Z-climate being the most significant. Both Z-scores were significantly related to the 1998 prevalence of diabetes (Z-climate: p = 0.00018; Z-environment: p = 0.0059) with the climate again being the most significant.
Conclusions: Increased temperature can increase magnesium sweat losses, which may not be compensated by diet or water intake. Climate relationships to these diseases need further investigation.
Key words: heart disease, heart deaths, diabetes, climate, temperature, precipitation, magnesium
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INTRODUCTION |
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These geographical variations also show a north-south variation besides the western and eastern variations. The northern parts of the United States are colder than the southern parts. Also the western parts of the country usually have less precipitation than the eastern parts. These climate variations were compared to the state death rates from heart disease for males and to the prevalence of diabetes for men and women combined. Environmental factors were also considered.
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METHODS |
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Six environmental factors were obtained from the 1990 census for each state [3] and included median value of housing units; percentage of households receiving interest, dividend, or net rental income; median household income; percentage of individuals over the age of 25 years who have completed high school; percentage of individuals over the age of 25 years who have completed college; and the percentage of workers employed in executive occupations [4]. A Z-score was calculated for these six environmental factors [4]. The summation of these six Z-scores is called Z-environment.
The yearly temperature and precipitation for the states, from 1990 to 1995, were obtained from the Western Regional Climate Center in the United States [5]. Z-scores were calculated from the temperature and precipitation. The summation of these two Z-scores is called Z-climate.
Temperature and precipitation were not available for Alaska and Hawaii, therefore these states were not included in Z-environment or Z-climate.
Z-scores were compared to the male heart death rates and to the prevalence of diabetes by correlations and also by tertiles of the Z-scores for analysis of variance (ANOVA) using NCSS 6.0 (Kaysville, Utah, USA). Comparisons of the tertiles used the Tukey-Kramer multiple-comparison test with a significance of 0.05.
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RESULTS |
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DISCUSSION |
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Increased climate scores are associated with increased temperature and precipitation, which can result in increased sweat losses of sodium (Na), potassium (K), calcium (Ca), and magnesium (Mg). Na and K should be easily compensated by a normal diet. Ca and Mg may not be. Sweat losses of Ca and Mg in a hot, humid environment with exercise were 1.3 mmol and 0.5 mmol/liter, respectively [6]. If two liters of sweat were lost a day, this would result in a loss of 104 mg of Ca and 24 mg of Mg. If 20% of Ca is absorbed, about 500 mg of additional Ca would be needed. If 20% of Mg is absorbed, 120 mg of Mg would be needed. However, for adults in the United States, the average diet Mg content is already about 100 mg less than the 1997 recommended dietary allowance of 420 mg for men and 320 mg for women [7]. These sweat losses could further compromise the already limited Mg intake. Thus climate conditions that increase sweat losses may contribute to Mg deficiency.
Another consideration is that the states with high precipitation usually have low water hardness, which would further limit Ca and Mg intake (unpublished data).
Low serum or plasma Mg has occurred with increased ischemic heart deaths from the National Health and Nutrition Survey II (NHANES II) [8], patients following a myocardial infarction [9], diabetes [10], insulin resistance [11] and was found to be a risk factor for development of type 2 diabetes [12]. Increased sweat losses of Mg may contribute to low serum or plasma Mg.
Increased health risks in some states may be associated with losses of critical minerals that are not compensated by diet or water. Low environmental Z-scores would be associated with low income which could decrease the quality of the food intake and limit both Ca and Mg intake. In addition, a low income would decrease housing options which could increase sweat losses. Therefore, a combination of low Z-environmental scores in combination with high Z-climate scores, could contribute to increased health risks of heart disease or diabetes.
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This article has been cited by other articles:
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  M. Schootman, E. M. Andresen, F. D. Wolinsky, T. K. Malmstrom, J. P. Miller, Y. Yan, and D. K. Miller The Effect of Adverse Housing and Neighborhood Conditions on the Development of Diabetes Mellitus among Middle-aged African Americans Am. J. Epidemiol., August 15, 2007; 166(4): 379 - 387. [Abstract] [Full Text] [PDF]
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