Married people tend to share lifestyle factors like physical activity, nutritional intake and use of alcohol and tobacco and same living environment such as stairs and carpets that can increase the risk of falling. A meta-analysis showed a substantial spousal concordance for smoking (odds ratio 3.25, 95 % confidence interval 2.94 to 3.59) [
29]. Bone mineral density was evaluated in a study of 104 spouses at age above 50 years and married for approximately 40 years. There was no spousal concordance for Z-score of BMD or in loss of bone density. However, there was an obvious concordance between partners concerning weight, height, BMI, muscle strength, physical activity, 25-hydroxyvitamin D
3, caloric intake and smoking [
30]. Married couples living at high latitudes, as in Scandinavia, are exposed to a shorter period of vitamin D production in the skin. Elderly people at rural areas tend to have lower risk for hip fracture compared to urban areas [
31]. Married couples have similar nutritional intake with impact on gut microbiota. Recent studies have indicated a possible impact of microbiota for several diseases like osteoporosis, atherosclerosis and diabetes [
32‐
34]. Spouses have a doubled risk for peptic ulcer, which might partly be explained by spousal concordance in Heliobacter colonisation [
20]. Spouses share lifestyle factors over many years especially in ages above 70 years in which there is a high incidence of fractures, cardiovascular and cancer. A meta-analysis showed spousal concordance for most risk factors in cardiovascular disease such as hypertension, smoking, diabetes and obesity. Authors therefore argue that interventions to reduce cardiovascular risk factors should be addressed to both members of a marital couple [
29]. A study of the importance of family factors and cancer was performed in the Swedish Family-Cancer Database (FCD) comprised of almost 15 million people coordinated with the Multigeneration Register. The results showed a significant familial risk for almost all types of cancer including colorectal, stomach, oesophagus, lung, urinary bladder and skin. The standardised incidence ratio (SIR) was higher also in first-degree relatives. However, SIR for oesophagus cancer was approximately 3.0 in spouses and 2.64 in first-degree relatives. The population attributable fraction for familial cancer was estimated to 6 % [
23]. Genetic factors and lifestyle factors often occur together. Studies have shown not only a strong heritability of smoking but also assortative mating for smoking among spouses explaining high SIRs for lung cancer both for first-degree relatives and spouses [
23]. Measures for preventing cancer, such as stopping smoking and sun protection, should be advocated both for relatives and married couples. A meta-analysis of spousal concordance for diabetes showed a 26 % increased diabetes risk after spousal history of diabetes. Authors argue for health interventions with increased physical activity and nutritional intervention among married couples to prevent diabetes [
35]. A recent study of 29,096 individuals with celiac disease in Sweden showed an increased risk for other autoimmune disease among both first-degree relatives and spouses indicating that in addition to genetic factors, also environmental factors contribute to the risk of autoimmunity [
36].