Marriage, cohabitation and mortality in Denmark: national cohort study of 6.5 million persons followed for up to three decades (1982–2011)
Fristch and Simonsen studied mortality according to marital status using a database of 6.5 million Danes that were followed over 12 years. Because of Denmarks extensive civil database system, they were able to access data on health and mortality without relying on self-reports. The causes of mortality were grouped according to marital status and for cohabitation for opposite sex and same sex unions. Studies of this type are particularly useful because they provide a large amount of data from the whole population over a long period of time. In addition, Denmark is relatively tolerant of homosexuality, which means that ‘homophobia’ or discrimination is less likely to a factor in any outcomes. For the purposes of comparison, they assigned ‘opposite sex marriages’ a hazard risk of 1.0 and compared other arrangements to this. For example, A hazard risk of 1.5 means that the arrangement was associated with 50% higher risk of mortality than opposite sex marriage.
They did the same with cohabiting relationships (assign opposite sex cohabiters a hazard risk of 1.0 and compare other ‘cohabitation’ arrangements to this). This means that they did not directly compare same sex married men/women with same sex cohabiting men/women. It is well-known however that hazard risks for married people are lower than those for cohabiters. For example, a study from Finland (Mortality differences According to Living Arrangements (Koskinen et al, International Journal of Epidemiology 2007; 36:1255-1264). This study was chosen because Finland has a population similar in many ways to Denmark and the authors analysed >200,000 deaths from 1996-2000. They found that cohabiting women and men had approximately 65% higher mortality than married ones. Although we are importing findings from another study, we can use them as modifiers to estimate the values that this study did not measure. Therefore the hazard ratios for cohabiters could be estimated at 1.5 when compared to married people at 1.0.
Key findings from the Danish study include:
1. People in opposite sex marriages had consistently lower mortality rates than ALL OTHER ARRANGEMENTS. This is consistent with previous research which shows significant health benefits to being married. It should be noted that vast majority of these studies were on OPPOSITE SEX couples as same sex ‘marriage’ is a relatively recent phenomenon. (For the purposes of comparison, they assigned opposite sex marriage a hazard ratio of 1.0
2. Widows, divorcees and unmarried mortality rates increased 40-70% for women and 20-70% for men.
3. Men in same sex marriages were 40% more likely to die from all causes than men in heterosexual marriages.
4. Same sex cohabiting men had 70% greater risk of mortality than opposite sex cohabiters . As discussed above, opposite sex male cohabiters already had 65% higher mortality than married men so same sex marriage drops mortality by AT BEST 5%.
5. Women in same sex marriages were 70-350% more likely to die than women in heterosexual marriages depending on age. Same sex cohabiting women had 104% greater mortality than opposite sex cohabiters who already had 65% higher mortality than opposite sex married women. This means that same sex marriage has made no significant difference to mortality rates for women.
6. Women in same sex marriages were >6 times more likely to commit suicide as those in opposite sex marriages.
7. Men in same sex marriages were 4x more likely to die from suicide as men in heterosexual marriages. These numbers are consistent with data from Sweden (Andersson et al, 2016) which showed that men in SSM were nearly 3x more likely to suicide.
8. Like other western societies, the most common causes of death for men were cardiovascular disease and cancer. Even when these were removed, along with suicide AND HIV/AIDS, Men in same sex marriages were still 60% more likely to die from ‘other causes’ than men in heterosexual marriages.
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