{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,12,14]],"date-time":"2025-12-14T16:58:07Z","timestamp":1765731487155,"version":"3.48.0"},"reference-count":42,"publisher":"BMJ","issue":"8","funder":[{"name":"Aimee Stacey Memorial Bequest"},{"name":"Ignacy Burnett Motor Neuron Disease Bequest"}],"content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Open"],"accepted":{"date-parts":[[2017,6,16]]},"published-print":{"date-parts":[[2017,8]]},"abstract":"<jats:sec>\n                    <jats:title>Objectives<\/jats:title>\n                    <jats:p>The ratio of the length of the index finger (2D) to the ring finger (4D) (2D:4D) has been reported to be lower (ie, 2D&lt;4D) in people with amyotrophic lateral sclerosis (ALS) than non-ALS controls. This has led to suggestions that exposure to increased prenatal testosterone, which also lowers this ratio, could be a risk factor for ALS. In an attempt to test this hypothesis, we examined 2D:4Ds from large numbers of patients with ALS and controls.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Setting<\/jats:title>\n                    <jats:p>An online multilingual questionnaire enabling respondents to measure their own index and ring finger lengths.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Participants<\/jats:title>\n                    <jats:p>Of the initial 949 respondents, 572 remained for analysis after elimination for inability to straighten fingers, not answering the question, statistical outliers and aged &lt;40 years. Respondents remaining for analysis were 202 patients with ALS (125 males, 77 females) and 370 non-ALS controls (112 males, 258 females).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>Unpaired t-tests with 95% CIs were used to assess differences in mean 2D:4Ds. Males had significantly lower mean 2D:4Ds than females, in both ALS and control groups, for both left and right hands. No significant differences were found in 2D:4Ds between ALS and control groups, in either males or females, for either left or right hands. Receiver operating characteristic curves showed no power for 2D:4Ds to predict ALS status in either males or females.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>2D:4Ds did not differ between patients with ALS and controls in this study. This was despite the dataset being large enough to confirm the established finding of lower 2D:4Ds in males compared with females. These findings do not support the hypothesis that exposure to increased prenatal testosterone is a risk factor for ALS. A putative lower 2D:4D has been proposed to explain the link between ALS and exercise, but our results indicate that other exercise-related factors are more likely to explain this association.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1136\/bmjopen-2017-016924","type":"journal-article","created":{"date-parts":[[2017,8,7]],"date-time":"2017-08-07T20:10:53Z","timestamp":1502136653000},"page":"e016924","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":5,"title":["Does the index-to-ring finger length ratio (2D:4D) differ in amyotrophic lateral sclerosis (ALS)? 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