Latitude gradient decreasing, female/male ratio increasing in MS Published Story by hollie
Individual studies have recently reported on what seems to be a decrease of the MS "latitude gradient" (the lower incidence rate toward the equator) and an increase in the ratio of females to males with MS. To test the overall validity of these indications, two epidemiologists compiled and analyzed MS incidence data from 27 different studies conducted in Europe, the US, and Australia. These studies covered different time periods that ranged from 1950 to 2002.
The analysis confirmed that over these decades, MS rates have been increasing more rapidly in lower latitudes than in higher ones. Also confirmed was the increase in the female:male ratio, which grew from 1.4 in 1955 to 2.3 in 2000. The authors suggest possible explanations for these findings. For instance, changes in lifestyle and living conditions at lower latitudes may result in decreasing exposure to sunlight (and thus lower vitamin D levels) and decreasing exposure to infections at younger ages.
The female:male ratio may have been affected by an increase among women in smoking, which has been associated with MS, or perhaps reproductive factors (although none of these have yet been associated with MS).
One of the limitations pointed out by the authors was that this was not truly a worldwide study due to the shortage of incidence figures from Africa, Asia, and Central/South America. It would be very interesting to study the gender ratio in these regions, for instance, to see whether the explanations put forth remain plausible and/or whether new ones emerge.
Latitude gradient decreasing, female/male ratio increasing in MS Published Story by hollie
Individual studies have recently reported on what seems to be a decrease of the MS "latitude gradient" (the lower incidence rate toward the equator) and an increase in the ratio of females to males with MS. To test the overall validity of these indications, two epidemiologists compiled and analyzed MS incidence data from 27 different studies conducted in Europe, the US, and Australia. These studies covered different time periods that ranged from 1950 to 2002.
The analysis confirmed that over these decades, MS rates have been increasing more rapidly in lower latitudes than in higher ones. Also confirmed was the increase in the female:male ratio, which grew from 1.4 in 1955 to 2.3 in 2000. The authors suggest possible explanations for these findings. For instance, changes in lifestyle and living conditions at lower latitudes may result in decreasing exposure to sunlight (and thus lower vitamin D levels) and decreasing exposure to infections at younger ages.
The female:male ratio may have been affected by an increase among women in smoking, which has been associated with MS, or perhaps reproductive factors (although none of these have yet been associated with MS).
One of the limitations pointed out by the authors was that this was not truly a worldwide study due to the shortage of incidence figures from Africa, Asia, and Central/South America. It would be very interesting to study the gender ratio in these regions, for instance, to see whether the explanations put forth remain plausible and/or whether new ones emerge.