Paternal age and schizophrenia
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《英国医生杂志》
EDITOR—Sipos et al set themselves the task of showing the presence of a higher than average paternal age in schizophrenia and that this phenomenon is restricted only to cases with a low family history for the disease.1 Both hypotheses are confirmed with statistical significance in their study.
This is interesting, but the sample studied is biased, which casts serious doubts on the validity of the results. The study includes only subjects with an age at onset between 16 and 38. The literature on schizophrenia shows that to generalise the results obtained from a limited age sample is dangerous. Often differences that seem highly significant in age biased samples even up when the cohorts are followed up throughout their lifetime. The aetiological factors in schizophrenia are probably the same at all ages qualitatively but seem to vary greatly quantitatively.2
The male to female ratio in the incidence and prevalence of schizophrenia is a cautionary tale. The incidence is significantly higher in men than in women in age groups up to the mid-30s, but the ratio of men to women becomes inverted with age, reaching 1:2 for onset after 40 years of age and 1:6 after 60. Eventually the lifetime morbid risk is the same in both sexes.3
The results of the study by Sipos et al are therefore intriguing but must be interpreted cautiously. No stratification can correct the above bias. Only the follow up of this cohort for at least a further 15 years can offer reliable results.
Marco Procopio, consultant psychiatrist
Priory Hospital Hove, Hove, East Sussex BN3 4FH marcoprocopio00@hotmail.com
Competing interests: None declared.
References
Sipos A, Rasmussen F, Harrison G, Tynelius P, Lewis G, Leon DA, Gunnell D. Paternal age and schizophrenia: a population based cohort study. BMJ 2004;329: 1070-3. (6 November.)
Kendler KS, Karkowski-Shuman L, Walsh D. Age at onset in schizophrenia and risk of illness in relatives. Br J Psychiatry 1996;169: 213-8.
Jablenski A, Sartorius N, Ernberg G, Anker M, Korten A, Cooper JE, et al. Schizophrenia: manifestations, incidence and course in different cultures. A World Health Organisation 10-country study. Psychol Med 1992;20(suppl): 1-97.
This is interesting, but the sample studied is biased, which casts serious doubts on the validity of the results. The study includes only subjects with an age at onset between 16 and 38. The literature on schizophrenia shows that to generalise the results obtained from a limited age sample is dangerous. Often differences that seem highly significant in age biased samples even up when the cohorts are followed up throughout their lifetime. The aetiological factors in schizophrenia are probably the same at all ages qualitatively but seem to vary greatly quantitatively.2
The male to female ratio in the incidence and prevalence of schizophrenia is a cautionary tale. The incidence is significantly higher in men than in women in age groups up to the mid-30s, but the ratio of men to women becomes inverted with age, reaching 1:2 for onset after 40 years of age and 1:6 after 60. Eventually the lifetime morbid risk is the same in both sexes.3
The results of the study by Sipos et al are therefore intriguing but must be interpreted cautiously. No stratification can correct the above bias. Only the follow up of this cohort for at least a further 15 years can offer reliable results.
Marco Procopio, consultant psychiatrist
Priory Hospital Hove, Hove, East Sussex BN3 4FH marcoprocopio00@hotmail.com
Competing interests: None declared.
References
Sipos A, Rasmussen F, Harrison G, Tynelius P, Lewis G, Leon DA, Gunnell D. Paternal age and schizophrenia: a population based cohort study. BMJ 2004;329: 1070-3. (6 November.)
Kendler KS, Karkowski-Shuman L, Walsh D. Age at onset in schizophrenia and risk of illness in relatives. Br J Psychiatry 1996;169: 213-8.
Jablenski A, Sartorius N, Ernberg G, Anker M, Korten A, Cooper JE, et al. Schizophrenia: manifestations, incidence and course in different cultures. A World Health Organisation 10-country study. Psychol Med 1992;20(suppl): 1-97.