Dr. Tea Skaaby and colleagues of the Research Centre for Prevention and Health at Glostrup Hospital in Denmark, just published the latest study looking at vitamin D levels and death rates. This was the first study that investigated the association of vitamin D status and different specific causes of death in the same study population.
Skaaby T, Husemoen LLN, Pisinger C, Jørgensen T, Thuesen BH, et al. (2012) Vitamin D Status and Cause-Specific Mortality: A General Population Study. PLoS ONE 7(12): e52423. doi:10.1371/journal.pone.0052423
They studied 9,146 individuals from two different cohorts (groups) from as early as 1993 to the end of 2009 that had frozen blood samples from the beginning of their enrollment and assayed vitamin D levels. Over the years, there were a total of 832 deaths, with a median follow-up of about 10 years.
They split the vitamin D levels into four equal groups (quartiles). For the largest of their two cohorts, the lowest one-fourth had average 25(OH)D levels of 9 ng/ml, the second quartile had a mean of 16 ng/ml, the third quartile had a mean of 22 ng/ml and the highest quartile had a mean of 32 ng/ml.
They found significant associations between vitamin D status and death caused by diseases of the respiratory system (Hazard Ratio or HR=.26), the digestive system (HR=.28), and endocrine, nutritional and metabolic diseases (HR=.21) for the fourth vitamin D quartile compared to the first. However, unlike most other studies, they found no association between vitamin D status and death caused by cancer or cardiovascular disease. I don’t know why such associations were not found, as so many other studies have found such associations.
The authors concluded,
“We found significant inverse associations between vitamin D status and death caused by diseases of the endocrine, the respiratory, and the digestive system but no associations with death caused by neoplasms or diseases of the circulatory system. Due to the explorative nature of the study and the low number of events in some of the disease categories, the results need to be confirmed in other studies. The results, however, suggest that we also look elsewhere (than to cardiovascular disease and cancer) to explain the inverse association between vitamin D status and mortality.”
What was remarkable about this Skaaby et al Danish paper was the breathtaking array of diseases associated with vitamin D deficiency. Even neurological illnesses had a trend towards reduced mortality with higher vitamin D levels.