Population mortality and morbidity studies suggest there is a slight but not significant lowering of life expectancy in individuals with Klinefelter syndrome (KS). The average lifespan has been found to be reduced by 1.5 to 2 years, with morbidity and mortality increased due to a wide number of conditions, including diabetes, cerebrovascular disease, and breast cancer.[43]Swerdlow AJ, Higgins CD, Schoemaker MJ, et al. Mortality in patients with Klinefelter syndrome in Britain: a cohort study. J Clin Endocrinol Metab. 2005 Dec;90(12):6516-22.
https://www.doi.org/10.1210/jc.2005-1077
http://www.ncbi.nlm.nih.gov/pubmed/16204366?tool=bestpractice.com
[44]Bojesen A, Juul S, Birkebaek NH, et al. Morbidity in Klinefelter syndrome: a Danish register study based on hospital discharge diagnoses. J Clin Endocrinol Metab. 2006 Apr;91(4):1254-60.
https://www.doi.org/10.1210/jc.2005-0697
http://www.ncbi.nlm.nih.gov/pubmed/16394093?tool=bestpractice.com
Higher rates of osteoporosis and fractures are also important to note.[4]Gravholt CH, Chang S, Wallentin M, et al. Klinefelter syndrome: integrating genetics, neuropsychology, and endocrinology. Endocr Rev. 2018 Aug 1;39(4):389-423.
https://www.doi.org/10.1210/er.2017-00212
http://www.ncbi.nlm.nih.gov/pubmed/29438472?tool=bestpractice.com
[7]Ridder LO, Berglund A, Stochholm K, et al. Morbidity, mortality, and socioeconomics in Klinefelter syndrome and 47,XYY syndrome: a comparative review. Endocr Connect. 2023 May 1;12(5):e230024.
https://www.doi.org/10.1530/EC-23-0024
http://www.ncbi.nlm.nih.gov/pubmed/37098811?tool=bestpractice.com
Appropriate treatment with testosterone can alleviate the portion of excess risk that is due to conditions associated with hypergonadotropic hypogonadism, but some of the elevated risk is likely intrinsic to the chromosome aberration and therefore not corrected by testosterone treatment.[3]Zitzmann M, Aksglaede L, Corona G, et al. European Academy of Andrology guidelines on Klinefelter syndrome. Endorsing organization: European Society of Endocrinology. Andrology. 2021 Jan;9(1):145-67.
https://www.doi.org/10.1111/andr.12909
http://www.ncbi.nlm.nih.gov/pubmed/32959490?tool=bestpractice.com
The increased morbidity and mortality in individuals with KS may also be partially explained by their often lower socioeconomic status, with cohort data suggesting shorter education, higher rates of unemployment, lower average incomes, and earlier average age at retirement compared with men without KS.[1]Groth KA, Skakkebæk A, Høst C, et al. Clinical review: Klinefelter syndrome - a clinical update. J Clin Endocrinol Metab. 2013 Jan;98(1):20-30.
https://www.doi.org/10.1210/jc.2012-2382
http://www.ncbi.nlm.nih.gov/pubmed/23118429?tool=bestpractice.com
[4]Gravholt CH, Chang S, Wallentin M, et al. Klinefelter syndrome: integrating genetics, neuropsychology, and endocrinology. Endocr Rev. 2018 Aug 1;39(4):389-423.
https://www.doi.org/10.1210/er.2017-00212
http://www.ncbi.nlm.nih.gov/pubmed/29438472?tool=bestpractice.com
[7]Ridder LO, Berglund A, Stochholm K, et al. Morbidity, mortality, and socioeconomics in Klinefelter syndrome and 47,XYY syndrome: a comparative review. Endocr Connect. 2023 May 1;12(5):e230024.
https://www.doi.org/10.1530/EC-23-0024
http://www.ncbi.nlm.nih.gov/pubmed/37098811?tool=bestpractice.com
It is important to note that most boys and men with KS are never diagnosed so the reported data likely reflects more severe phenotypes of the condition.